draft-ietf-cellar-ffv1-v4-17.txt   draft-ietf-cellar-ffv1-v4-18.txt 
cellar M. Niedermayer cellar M. Niedermayer
Internet-Draft Internet-Draft
Intended status: Standards Track D. Rice Intended status: Standards Track D. Rice
Expires: 26 November 2021 Expires: 31 May 2022
J. Martinez J. Martinez
25 May 2021 27 November 2021
FFV1 Video Coding Format Version 4 FFV1 Video Coding Format Version 4
draft-ietf-cellar-ffv1-v4-17 draft-ietf-cellar-ffv1-v4-18
Abstract Abstract
This document defines FFV1, a lossless intra-frame video encoding This document defines FFV1, a lossless, intra-frame video encoding
format. FFV1 is designed to efficiently compress video data in a format. FFV1 is designed to efficiently compress video data in a
variety of pixel formats. Compared to uncompressed video, FFV1 variety of pixel formats. Compared to uncompressed video, FFV1
offers storage compression, frame fixity, and self-description, which offers storage compression, frame fixity, and self-description, which
makes FFV1 useful as a preservation or intermediate video format. makes FFV1 useful as a preservation or intermediate video format.
Status of This Memo Status of This Memo
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Notation and Conventions . . . . . . . . . . . . . . . . . . 4 2. Notation and Conventions . . . . . . . . . . . . . . . . . . 4
2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.1. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 6 2.2.1. Pseudocode . . . . . . . . . . . . . . . . . . . . . 6
2.2.2. Arithmetic Operators . . . . . . . . . . . . . . . . 6 2.2.2. Arithmetic Operators . . . . . . . . . . . . . . . . 6
2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 7 2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 7
2.2.4. Comparison Operators . . . . . . . . . . . . . . . . 7 2.2.4. Comparison Operators . . . . . . . . . . . . . . . . 7
2.2.5. Mathematical Functions . . . . . . . . . . . . . . . 7 2.2.5. Mathematical Functions . . . . . . . . . . . . . . . 7
2.2.6. Order of Operation Precedence . . . . . . . . . . . . 8 2.2.6. Order of Operation Precedence . . . . . . . . . . . . 8
2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 9 2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 9
2.2.9. Bitstream Functions . . . . . . . . . . . . . . . . . 9 2.2.9. Bitstream Functions . . . . . . . . . . . . . . . . . 9
3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 9 3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3. Median Predictor . . . . . . . . . . . . . . . . . . . . 11 3.3. Median Predictor . . . . . . . . . . . . . . . . . . . . 11
3.3.1. Exception . . . . . . . . . . . . . . . . . . . . . . 11 3.3.1. Exception . . . . . . . . . . . . . . . . . . . . . . 11
3.4. Quantization Table Sets . . . . . . . . . . . . . . . . . 12 3.4. Quantization Table Sets . . . . . . . . . . . . . . . . . 12
3.5. Context . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.5. Context . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 13 3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 13
3.7. Color spaces . . . . . . . . . . . . . . . . . . . . . . 13 3.7. Color Spaces . . . . . . . . . . . . . . . . . . . . . . 13
3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 13 3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 13
3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.8. Coding of the Sample Difference . . . . . . . . . . . . . 16 3.8. Coding of the Sample Difference . . . . . . . . . . . . . 16
3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 16 3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 16
3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 23 3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 23
4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.1. Quantization Table Set . . . . . . . . . . . . . . . . . 30 4.1. Quantization Table Set . . . . . . . . . . . . . . . . . 30
4.1.1. quant_tables . . . . . . . . . . . . . . . . . . . . 31 4.1.1. quant_tables . . . . . . . . . . . . . . . . . . . . 31
4.1.2. context_count . . . . . . . . . . . . . . . . . . . . 32 4.1.2. context_count . . . . . . . . . . . . . . . . . . . . 31
4.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 32 4.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 31
4.2.1. version . . . . . . . . . . . . . . . . . . . . . . . 34 4.2.1. version . . . . . . . . . . . . . . . . . . . . . . . 33
4.2.2. micro_version . . . . . . . . . . . . . . . . . . . . 34 4.2.2. micro_version . . . . . . . . . . . . . . . . . . . . 33
4.2.3. coder_type . . . . . . . . . . . . . . . . . . . . . 35 4.2.3. coder_type . . . . . . . . . . . . . . . . . . . . . 34
4.2.4. state_transition_delta . . . . . . . . . . . . . . . 36 4.2.4. state_transition_delta . . . . . . . . . . . . . . . 35
4.2.5. colorspace_type . . . . . . . . . . . . . . . . . . . 36 4.2.5. colorspace_type . . . . . . . . . . . . . . . . . . . 35
4.2.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 37 4.2.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 36
4.2.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 37 4.2.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 36
4.2.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 38 4.2.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 37
4.2.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 38 4.2.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 37
4.2.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 38 4.2.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 37
4.2.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 38 4.2.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 37
4.2.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 39 4.2.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 38
4.2.13. quant_table_set_count . . . . . . . . . . . . . . . . 39 4.2.13. quant_table_set_count . . . . . . . . . . . . . . . . 38
4.2.14. states_coded . . . . . . . . . . . . . . . . . . . . 39 4.2.14. states_coded . . . . . . . . . . . . . . . . . . . . 38
4.2.15. initial_state_delta . . . . . . . . . . . . . . . . . 39 4.2.15. initial_state_delta . . . . . . . . . . . . . . . . . 38
4.2.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.2.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.2.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 40 4.2.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 39
4.3. Configuration Record . . . . . . . . . . . . . . . . . . 40 4.3. Configuration Record . . . . . . . . . . . . . . . . . . 39
4.3.1. reserved_for_future_use . . . . . . . . . . . . . . . 41 4.3.1. reserved_for_future_use . . . . . . . . . . . . . . . 40
4.3.2. configuration_record_crc_parity . . . . . . . . . . . 41 4.3.2. configuration_record_crc_parity . . . . . . . . . . . 40
4.3.3. Mapping FFV1 into Containers . . . . . . . . . . . . 41 4.3.3. Mapping FFV1 into Containers . . . . . . . . . . . . 40
4.4. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.4. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.5. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.5. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.6. Slice Header . . . . . . . . . . . . . . . . . . . . . . 45 4.6. Slice Header . . . . . . . . . . . . . . . . . . . . . . 43
4.6.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 45 4.6.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 44
4.6.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 45 4.6.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 44
4.6.3. slice_width . . . . . . . . . . . . . . . . . . . . . 45 4.6.3. slice_width . . . . . . . . . . . . . . . . . . . . . 44
4.6.4. slice_height . . . . . . . . . . . . . . . . . . . . 46 4.6.4. slice_height . . . . . . . . . . . . . . . . . . . . 44
4.6.5. quant_table_set_index_count . . . . . . . . . . . . . 46 4.6.5. quant_table_set_index_count . . . . . . . . . . . . . 45
4.6.6. quant_table_set_index . . . . . . . . . . . . . . . . 46 4.6.6. quant_table_set_index . . . . . . . . . . . . . . . . 45
4.6.7. picture_structure . . . . . . . . . . . . . . . . . . 46 4.6.7. picture_structure . . . . . . . . . . . . . . . . . . 45
4.6.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 47 4.6.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 45
4.6.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 47 4.6.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 46
4.6.10. reset_contexts . . . . . . . . . . . . . . . . . . . 47 4.6.10. reset_contexts . . . . . . . . . . . . . . . . . . . 46
4.6.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 47 4.6.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 46
4.7. Slice Content . . . . . . . . . . . . . . . . . . . . . . 48 4.7. Slice Content . . . . . . . . . . . . . . . . . . . . . . 46
4.7.1. primary_color_count . . . . . . . . . . . . . . . . . 48 4.7.1. primary_color_count . . . . . . . . . . . . . . . . . 47
4.7.2. plane_pixel_height . . . . . . . . . . . . . . . . . 48 4.7.2. plane_pixel_height . . . . . . . . . . . . . . . . . 47
4.7.3. slice_pixel_height . . . . . . . . . . . . . . . . . 49 4.7.3. slice_pixel_height . . . . . . . . . . . . . . . . . 47
4.7.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 49 4.7.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 47
4.8. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 49 4.8. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.8.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 49 4.8.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 48
4.8.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 50 4.8.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 48
4.8.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 50 4.8.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 48
4.8.4. sample_difference . . . . . . . . . . . . . . . . . . 50 4.8.4. sample_difference . . . . . . . . . . . . . . . . . . 49
4.9. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 50 4.9. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 49
4.9.1. slice_size . . . . . . . . . . . . . . . . . . . . . 51 4.9.1. slice_size . . . . . . . . . . . . . . . . . . . . . 49
4.9.2. error_status . . . . . . . . . . . . . . . . . . . . 51 4.9.2. error_status . . . . . . . . . . . . . . . . . . . . 49
4.9.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 51 4.9.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 50
5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 51 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 50
6. Security Considerations . . . . . . . . . . . . . . . . . . . 52 6. Security Considerations . . . . . . . . . . . . . . . . . . . 51
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 51
7.1. Media Type Definition . . . . . . . . . . . . . . . . . . 52 7.1. Media Type Definition . . . . . . . . . . . . . . . . . . 51
8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 54 8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9. Normative References . . . . . . . . . . . . . . . . . . . . 54 9. Normative References . . . . . . . . . . . . . . . . . . . . 53
10. Informative References . . . . . . . . . . . . . . . . . . . 55 10. Informative References . . . . . . . . . . . . . . . . . . . 53
Appendix A. Multi-theaded decoder implementation suggestions . . 56 Appendix A. Multithreaded Decoder Implementation Suggestions . . 55
Appendix B. Future handling of some streams created by non Appendix B. Future Handling of Some Streams Created by
conforming encoders . . . . . . . . . . . . . . . . . . . 57 Nonconforming Encoders . . . . . . . . . . . . . . . . . 56
Appendix C. FFV1 Implementations . . . . . . . . . . . . . . . . 57 Appendix C. FFV1 Implementations . . . . . . . . . . . . . . . . 56
C.1. FFmpeg FFV1 Codec . . . . . . . . . . . . . . . . . . . . 57 C.1. FFmpeg FFV1 Codec . . . . . . . . . . . . . . . . . . . . 56
C.2. FFV1 Decoder in Go . . . . . . . . . . . . . . . . . . . 57 C.2. FFV1 Decoder in Go . . . . . . . . . . . . . . . . . . . 56
C.3. MediaConch . . . . . . . . . . . . . . . . . . . . . . . 58 C.3. MediaConch . . . . . . . . . . . . . . . . . . . . . . . 57
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 58 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 57
1. Introduction 1. Introduction
This document describes FFV1, a lossless video encoding format. The This document describes FFV1, a lossless video encoding format. The
design of FFV1 considers the storage of image characteristics, data design of FFV1 considers the storage of image characteristics, data
fixity, and the optimized use of encoding time and storage fixity, and the optimized use of encoding time and storage
requirements. FFV1 is designed to support a wide range of lossless requirements. FFV1 is designed to support a wide range of lossless
video applications such as long-term audiovisual preservation, video applications such as long-term audiovisual preservation,
scientific imaging, screen recording, and other video encoding scientific imaging, screen recording, and other video encoding
scenarios that seek to avoid the generational loss of lossy video scenarios that seek to avoid the generational loss of lossy video
encodings. encodings.
This document defines a version 4 of FFV1. Prior versions of FFV1 This document defines a version 4 of FFV1. Prior versions of FFV1
are defined within [I-D.ietf-cellar-ffv1]. are defined within [I-D.ietf-cellar-ffv1].
This document assumes familiarity with mathematical and coding This document assumes familiarity with mathematical and coding
concepts such as Range coding [range-coding] and YCbCr color spaces concepts such as Range encoding [Range-Encoding] and YCbCr color
[YCbCr]. spaces [YCbCr].
This specification describes the valid bitstream and how to decode This specification describes the valid bitstream and how to decode
such valid bitstream. Bitstreams not conforming to this it. Nonconformant bitstreams and the nonconformant handling of
specification or how they are handled is outside this specification. bitstreams are outside this specification. A decoder can perform any
A decoder could reject every invalid bitstream or attempt to perform action that it deems appropriate for an invalid bitstream: reject the
error concealment or re-download or use a redundant copy of the bitstream, attempt to perform error concealment, or re-download or
invalid part or any other action it deems appropriate. use a redundant copy of the invalid part.
2. Notation and Conventions 2. Notation and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2.1. Definitions 2.1. Definitions
"FFV1": chosen name of this video encoding format, short version of FFV1: The chosen name of this video encoding format, which is the
"FF Video 1", the letters "FF" coming from "FFmpeg", the name of the short version of "FF Video 1". The letters "FF" come from
reference decoder, whose first letters originally meant "Fast "FFmpeg", which is the name of the reference decoder whose first
Forward". letters originally meant "Fast Forward".
"Container": Format that encapsulates Frames (see Section 4.4) and Container: A format that encapsulates Frames (see Section 4.4) and
(when required) a "Configuration Record" into a bitstream. (when required) a Configuration Record into a bitstream.
"Sample": The smallest addressable representation of a color Sample: The smallest addressable representation of a color component
component or a luma component in a Frame. Examples of Sample are or a luma component in a Frame. Examples of Sample are Luma (Y),
Luma (Y), Blue-difference Chroma (Cb), Red-difference Chroma (Cr), Blue-difference Chroma (Cb), Red-difference Chroma (Cr),
Transparency, Red, Green, and Blue. Transparency, Red, Green, and Blue.
"Symbol": A value stored in the bitstream, which is defined and Symbol: A value stored in the bitstream, which is defined and
decoded through one of the methods described in Table 4. decoded through one of the methods described in Table 4.
"Line": A discrete component of a static image composed of Samples Line: A discrete component of a static image composed of Samples
that represent a specific quantification of Samples of that image. that represent a specific quantification of Samples of that image.
"Plane": A discrete component of a static image composed of Lines Plane: A discrete component of a static image composed of Lines that
that represent a specific quantification of Lines of that image. represent a specific quantification of Lines of that image.
"Pixel": The smallest addressable representation of a color in a Pixel: The smallest addressable representation of a color in a
Frame. It is composed of one or more Samples. Frame. It is composed of one or more Samples.
"MSB": Most Significant Bit, the bit that can cause the largest MSB: Most Significant Bit, the bit that can cause the largest change
change in magnitude of the Symbol. in magnitude of the symbol.
"VLC": Variable Length Code, a code that maps source symbols to a VLC: Variable Length Code, a code that maps source symbols to a
variable number of bits. variable number of bits.
"RGB": A reference to the method of storing the value of a Pixel by RGB: A reference to the method of storing the value of a pixel by
using three numeric values that represent Red, Green, and Blue. using three numeric values that represent Red, Green, and Blue.
"YCbCr": A reference to the method of storing the value of a Pixel by YCbCr: A reference to the method of storing the value of a pixel by
using three numeric values that represent the luma of the Pixel (Y) using three numeric values that represent the luma of the pixel
and the chroma of the Pixel (Cb and Cr). YCbCr word is used for (Y) and the chroma of the pixel (Cb and Cr). The term YCbCr is
historical reasons and currently references any color space relying used for historical reasons and currently references any color
on 1 luma Sample and 2 chroma Samples, e.g. YCbCr, YCgCo or ICtCp. space relying on one luma Sample and two chroma Samples, e.g.,
The exact meaning of the three numeric values is unspecified. YCbCr (luma, blue-difference chroma, red-difference chroma),
YCgCo, or ICtCp (intensity, blue-yellow, red-green).
"TBA": To Be Announced. Used in reference to the development of TBA: To Be Announced. Used in reference to the development of
future iterations of the FFV1 specification. future iterations of the FFV1 specification.
2.2. Conventions 2.2. Conventions
2.2.1. Pseudo-code 2.2.1. Pseudocode
The FFV1 bitstream is described in this document using pseudo-code. The FFV1 bitstream is described in this document using pseudocode.
Note that the pseudo-code is used for clarity in order to illustrate Note that the pseudocode is used to illustrate the structure of FFV1
the structure of FFV1 and not intended to specify any particular and is not intended to specify any particular implementation. The
implementation. The pseudo-code used is based upon the C programming pseudocode used is based upon the C programming language
language [ISO.9899.2018] and uses its "if/else", "while" and "for" [ISO.9899.2018] and uses its if/else, while, and for keywords as well
keywords as well as functions defined within this document. as functions defined within this document.
In some instances, pseudo-code is presented in a two-column format In some instances, pseudocode is presented in a two-column format
such as shown in Figure 1. In this form the "type" column provides a such as shown in Figure 1. In this form, the type column provides a
Symbol as defined in Table 4 that defines the storage of the data symbol as defined in Table 4 that defines the storage of the data
referenced in that same line of pseudo-code. referenced in that same line of pseudocode.
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
ExamplePseudoCode( ) { | ExamplePseudoCode( ) { |
value | ur value | ur
} | } |
Figure 1: A depiction of type-labelled pseudo-code used within Figure 1: A depiction of type-labeled pseudocode used within this
this document. document.
2.2.2. Arithmetic Operators 2.2.2. Arithmetic Operators
Note: the operators and the order of precedence are the same as used Note: the operators and the order of precedence are the same as used
in the C programming language [ISO.9899.2018], with the exception of in the C programming language [ISO.9899.2018], with the exception of
">>" (removal of implementation defined behavior) and "^" (power >> (removal of implementation-defined behavior) and ^ (power instead
instead of XOR) operators which are re-defined within this section. of XOR) operators, which are redefined within this section.
"a + b" means a plus b. a + b means a plus b.
"a - b" means a minus b. a - b means a minus b.
"-a" means negation of a. -a means negation of a.
"a * b" means a multiplied by b. a * b means a multiplied by b.
"a / b" means a divided by b. a / b means a divided by b.
"a ^ b" means a raised to the b-th power. a ^ b means a raised to the b-th power.
"a & b" means bit-wise "and" of a and b. a & b means bit-wise "and" of a and b.
"a | b" means bit-wise "or" of a and b. a | b means bit-wise "or" of a and b.
"a >> b" means arithmetic right shift of two's complement integer a >> b means arithmetic right shift of the two's complement integer
representation of a by b binary digits. This is equivalent to representation of a by b binary digits. This is equivalent to
dividing a by 2, b times, with rounding toward negative infinity. dividing a by 2, b times, with rounding toward negative infinity.
"a << b" means arithmetic left shift of two's complement integer a << b means arithmetic left shift of the two's complement integer
representation of a by b binary digits. representation of a by b binary digits.
2.2.3. Assignment Operators 2.2.3. Assignment Operators
"a = b" means a is assigned b. a = b means a is assigned b.
"a++" is equivalent to a is assigned a + 1. a++ is equivalent to a is assigned a + 1.
"a--" is equivalent to a is assigned a - 1. a-- is equivalent to a is assigned a - 1.
"a += b" is equivalent to a is assigned a + b. a += b is equivalent to a is assigned a + b.
"a -= b" is equivalent to a is assigned a - b. a -= b is equivalent to a is assigned a - b.
"a *= b" is equivalent to a is assigned a * b. a *= b is equivalent to a is assigned a * b.
2.2.4. Comparison Operators 2.2.4. Comparison Operators
"a > b" is true when a is greater than b. a > b is true when a is greater than b.
"a >= b" is true when a is greater than or equal to b. a >= b is true when a is greater than or equal to b.
"a < b" is true when a is less than b. a < b is true when a is less than b.
"a <= b" is true when a is less than or equal b. a <= b is true when a is less than or equal b.
"a == b" is true when a is equal to b. a == b is true when a is equal to b.
"a != b" is true when a is not equal to b. a != b is true when a is not equal to b.
"a && b" is true when both a is true and b is true. a && b is true when both a is true and b is true.
"a || b" is true when either a is true or b is true. a || b is true when either a is true or b is true.
"!a" is true when a is not true. !a is true when a is not true.
"a ? b : c" if a is true, then b, otherwise c. a ? b : c if a is true, then b, otherwise c.
2.2.5. Mathematical Functions 2.2.5. Mathematical Functions
"floor(a)" means the largest integer less than or equal to a. floor(a) means the largest integer less than or equal to a.
"ceil(a)" means the smallest integer greater than or equal to a. ceil(a) means the smallest integer greater than or equal to a.
"sign(a)" extracts the sign of a number, i.e. if a < 0 then -1, else sign(a) extracts the sign of a number, i.e., if a < 0 then -1, else
if a > 0 then 1, else 0. if a > 0 then 1, else 0.
"abs(a)" means the absolute value of a, i.e. "abs(a)" = "sign(a) * abs(a) means the absolute value of a, i.e., abs(a) = sign(a) * a.
a".
"log2(a)" means the base-two logarithm of a. log2(a) means the base-two logarithm of a.
"min(a,b)" means the smaller of two values a and b. min(a,b) means the smaller of two values a and b.
"max(a,b)" means the larger of two values a and b. max(a,b) means the larger of two values a and b.
"median(a,b,c)" means the numerical middle value in a data set of a, median(a,b,c) means the numerical middle value in a data set of a, b,
b, and c, i.e. a+b+c-min(a,b,c)-max(a,b,c). and c, i.e., a+b+c-min(a,b,c)-max(a,b,c).
"A ==> B" means A implies B. a ==> b means a implies b.
"A <==> B" means A ==> B , B ==> A. a <==> b means a ==> b , b ==> a.
a_b means the b-th value of a sequence of a a_b means the b-th value of a sequence of a.
a_(b,c) means the 'b,c'-th value of a sequence of a a_(b,c) means the 'b,c'-th value of a sequence of a.
2.2.6. Order of Operation Precedence 2.2.6. Order of Operation Precedence
When order of precedence is not indicated explicitly by use of When order of precedence is not indicated explicitly by use of
parentheses, operations are evaluated in the following order (from parentheses, operations are evaluated in the following order (from
top to bottom, operations of same precedence being evaluated from top to bottom, operations of same precedence being evaluated from
left to right). This order of operations is based on the order of left to right). This order of operations is based on the order of
operations used in Standard C. operations used in Standard C.
a++, a-- a++, a--
skipping to change at page 9, line 7 skipping to change at page 9, line 7
a == b, a != b a == b, a != b
a & b a & b
a | b a | b
a && b a && b
a || b a || b
a ? b : c a ? b : c
a = b, a += b, a -= b, a *= b a = b, a += b, a -= b, a *= b
2.2.7. Range 2.2.7. Range
"a...b" means any value from a to b, inclusive. a...b means any value from a to b, inclusive.
2.2.8. NumBytes 2.2.8. NumBytes
"NumBytes" is a non-negative integer that expresses the size in 8-bit NumBytes is a nonnegative integer that expresses the size in 8-bit
octets of a particular FFV1 "Configuration Record" or "Frame". FFV1 octets of a particular FFV1 Configuration Record or Frame. FFV1
relies on its Container to store the "NumBytes" values; see relies on its container to store the NumBytes values; see
Section 4.3.3. Section 4.3.3.
2.2.9. Bitstream Functions 2.2.9. Bitstream Functions
2.2.9.1. remaining_bits_in_bitstream 2.2.9.1. remaining_bits_in_bitstream
"remaining_bits_in_bitstream( NumBytes )" means the count of remaining_bits_in_bitstream( NumBytes ) means the count of remaining
remaining bits after the pointer in that "Configuration Record" or bits after the pointer in that Configuration Record or Frame. It is
"Frame". It is computed from the "NumBytes" value multiplied by 8 computed from the NumBytes value multiplied by 8 minus the count of
minus the count of bits of that "Configuration Record" or "Frame" bits of that Configuration Record or Frame already read by the
already read by the bitstream parser. bitstream parser.
2.2.9.2. remaining_symbols_in_syntax 2.2.9.2. remaining_symbols_in_syntax
"remaining_symbols_in_syntax( )" is true as long as the RangeCoder remaining_symbols_in_syntax( ) is true as long as the range coder has
has not consumed all the given input bytes. not consumed all the given input bytes.
2.2.9.3. byte_aligned 2.2.9.3. byte_aligned
"byte_aligned( )" is true if "remaining_bits_in_bitstream( NumBytes byte_aligned( ) is true if remaining_bits_in_bitstream( NumBytes ) is
)" is a multiple of 8, otherwise false. a multiple of 8, otherwise false.
2.2.9.4. get_bits 2.2.9.4. get_bits
"get_bits( i )" is the action to read the next "i" bits in the get_bits( i ) is the action to read the next i bits in the bitstream,
bitstream, from most significant bit to least significant bit, and to from most significant bit to least significant bit, and to return the
return the corresponding value. The pointer is increased by "i". corresponding value. The pointer is increased by i.
3. Sample Coding 3. Sample Coding
For each "Slice" (as described in Section 4.5) of a Frame, the For each Slice (as described in Section 4.5) of a Frame, the Planes,
Planes, Lines, and Samples are coded in an order determined by the Lines, and Samples are coded in an order determined by the color
color space (see Section 3.7). Each Sample is predicted by the space (see Section 3.7). Each Sample is predicted by the median
median predictor as described in Section 3.3 from other Samples predictor as described in Section 3.3 from other Samples within the
within the same Plane and the difference is stored using the method same Plane, and the difference is stored using the method described
described in Section 3.8. in Section 3.8.
3.1. Border 3.1. Border
A border is assumed for each coded "Slice" for the purpose of the A border is assumed for each coded Slice for the purpose of the
median predictor and context according to the following rules: median predictor and context according to the following rules:
* one column of Samples to the left of the coded slice is assumed as * One column of Samples to the left of the coded Slice is assumed as
identical to the Samples of the leftmost column of the coded slice identical to the Samples of the leftmost column of the coded Slice
shifted down by one row. The value of the topmost Sample of the shifted down by one row. The value of the topmost Sample of the
column of Samples to the left of the coded slice is assumed to be column of Samples to the left of the coded Slice is assumed to be
"0" 0.
* one column of Samples to the right of the coded slice is assumed * One column of Samples to the right of the coded Slice is assumed
as identical to the Samples of the rightmost column of the coded as identical to the Samples of the rightmost column of the coded
slice Slice.
* an additional column of Samples to the left of the coded slice and * An additional column of Samples to the left of the coded Slice and
two rows of Samples above the coded slice are assumed to be "0" two rows of Samples above the coded Slice are assumed to be 0.
Figure 2 depicts a slice of 9 Samples "a,b,c,d,e,f,g,h,i" in a 3x3 Figure 2 depicts a Slice of nine Samples a,b,c,d,e,f,g,h,i in a
arrangement along with its assumed border. three-by-three arrangement along with its assumed border.
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | 0 | | 0 | 0 | 0 | | 0 | | 0 | 0 | | 0 | 0 | 0 | | 0 |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | 0 | | 0 | 0 | 0 | | 0 | | 0 | 0 | | 0 | 0 | 0 | | 0 |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | 0 | | a | b | c | | c | | 0 | 0 | | a | b | c | | c |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | a | | d | e | f | | f | | 0 | a | | d | e | f | | f |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | d | | g | h | i | | i | | 0 | d | | g | h | i | | i |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
Figure 2: A depiction of FFV1's assumed border for a set example Figure 2: A depiction of FFV1's assumed border for a set of
Samples. example Samples.
3.2. Samples 3.2. Samples
Relative to any Sample "X", six other relatively positioned Samples Relative to any Sample X, six other relatively positioned Samples
from the coded Samples and presumed border are identified according from the coded Samples and presumed border are identified according
to the labels used in Figure 3. The labels for these relatively to the labels used in Figure 3. The labels for these relatively
positioned Samples are used within the median predictor and context. positioned Samples are used within the median predictor and context.
+---+---+---+---+ +---+---+---+---+
| | | T | | | | | T | |
+---+---+---+---+ +---+---+---+---+
| |tl | t |tr | | |tl | t |tr |
+---+---+---+---+ +---+---+---+---+
| L | l | X | | | L | l | X | |
+---+---+---+---+ +---+---+---+---+
Figure 3: A depiction of how relatively positioned Samples are Figure 3: A depiction of how relatively positioned Samples are
referenced within this document. referenced within this document.
The labels for these relative Samples are made of the first letters The labels for these relative Samples are made of the first letters
of the words Top, Left and Right. of the words Top, Left, and Right.
3.3. Median Predictor 3.3. Median Predictor
The prediction for any Sample value at position "X" may be computed The prediction for any Sample value at position X may be computed
based upon the relative neighboring values of "l", "t", and "tl" via based upon the relative neighboring values of l, t, and tl via this
this equation: equation:
median(l, t, l + t - tl) median(l, t, l + t - tl)
Note, this prediction template is also used in [ISO.14495-1.1999] and Note that this prediction template is also used in [ISO.14495-1.1999]
[HuffYUV]. and [HuffYUV].
3.3.1. Exception 3.3.1. Exception
If "colorspace_type == 0 && bits_per_raw_sample == 16 && ( coder_type If colorspace_type == 0 && bits_per_raw_sample == 16 && ( coder_type
== 1 || coder_type == 2 )" (see Section 4.2.5, Section 4.2.7 and == 1 || coder_type == 2 ) (see Section 4.2.5, Section 4.2.7, and
Section 4.2.3), the following median predictor MUST be used: Section 4.2.3), the following median predictor MUST be used:
median(left16s, top16s, left16s + top16s - diag16s) median(left16s, top16s, left16s + top16s - diag16s)
where: where:
left16s = l >= 32768 ? ( l - 65536 ) : l left16s = l >= 32768 ? ( l - 65536 ) : l
top16s = t >= 32768 ? ( t - 65536 ) : t top16s = t >= 32768 ? ( t - 65536 ) : t
diag16s = tl >= 32768 ? ( tl - 65536 ) : tl diag16s = tl >= 32768 ? ( tl - 65536 ) : tl
Background: a two's complement 16-bit signed integer was used for Background: a two's complement 16-bit signed integer was used for
storing Sample values in all known implementations of FFV1 bitstream storing Sample values in all known implementations of FFV1 bitstream
(see Appendix C). So in some circumstances, the most significant bit (see Appendix C). So in some circumstances, the most significant bit
was wrongly interpreted (used as a sign bit instead of the 16th bit was wrongly interpreted (used as a sign bit instead of the 16th bit
of an unsigned integer). Note that when the issue was discovered, of an unsigned integer). Note that when the issue was discovered,
the only configuration of all known implementations being impacted is the only impacted configuration of all known implementations was the
16-bit YCbCr with no Pixel transformation with Range Coder coder, as 16-bit YCbCr with no pixel transformation and with the range coder
other potentially impacted configurations (e.g. 15/16-bit coder type, as the other potentially impacted configurations (e.g.,
JPEG2000-RCT with Range Coder coder, or 16-bit content with Golomb the 15/16-bit JPEG 2000 Reversible Color Transform (RCT)
Rice coder) were implemented nowhere [ISO.15444-1.2016]. In the
meanwhile, 16-bit JPEG2000-RCT with Range Coder coder was implemented [ISO.15444-1.2019] with range coder or the 16-bit content with the
without this issue in one implementation and validated by one Golomb Rice coder type) were not implemented. Meanwhile, the 16-bit
conformance checker. It is expected (to be confirmed) to remove this JPEG 2000 RCT with range coder was deployed without this issue in one
exception for the median predictor in the next version of the FFV1 implementation and validated by one conformance checker. It is
bitstream. expected (to be confirmed) that this exception for the median
predictor will be removed in the next version of the FFV1 bitstream.
3.4. Quantization Table Sets 3.4. Quantization Table Sets
Quantization Tables are used on Sample Differences (see Section 3.8), Quantization Tables are used on Sample Differences (see Section 3.8),
so Quantized Sample Differences are stored in the bitstream. so Quantized Sample Differences are stored in the bitstream.
The FFV1 bitstream contains one or more Quantization Table Sets. The FFV1 bitstream contains one or more Quantization Table Sets.
Each Quantization Table Set contains exactly 5 Quantization Tables Each Quantization Table Set contains exactly five Quantization Tables
with each Quantization Table corresponding to one of the five with each Quantization Table corresponding to one of the five
Quantized Sample Differences. For each Quantization Table, both the Quantized Sample Differences. For each Quantization Table, both the
number of quantization steps and their distribution are stored in the number of quantization steps and their distribution are stored in the
FFV1 bitstream; each Quantization Table has exactly 256 entries, and FFV1 bitstream; each Quantization Table has exactly 256 entries, and
the 8 least significant bits of the Quantized Sample Difference are the eight least significant bits of the Quantized Sample Difference
used as index: are used as an index:
Q_(j)[k] = quant_tables[i][j][k&255] Q_(j)[k] = quant_tables[i][j][k&255]
Figure 4 Figure 4: Description of the mapping from sample differences to the
corresponding Quantized Sample Differences.
In this formula, "i" is the Quantization Table Set index, "j" is the In this formula, i is the Quantization Table Set index, j is the
Quantized Table index, "k" the Quantized Sample Difference (see Quantized Table index, and k is the Quantized Sample Difference (see
Section 4.1.1). Section 4.1.1).
3.5. Context 3.5. Context
Relative to any Sample "X", the Quantized Sample Differences "L-l", Relative to any Sample X, the Quantized Sample Differences L-l, l-tl,
"l-tl", "tl-t", "T-t", and "t-tr" are used as context: tl-t, T-t, and t-tr are used as context:
context = Q_(0)[l - tl] + context = Q_(0)[l - tl] +
Q_(1)[tl - t] + Q_(1)[tl - t] +
Q_(2)[t - tr] + Q_(2)[t - tr] +
Q_(3)[L - l] + Q_(3)[L - l] +
Q_(4)[T - t] Q_(4)[T - t]
Figure 5 Figure 5: Description of the computing of the Context.
If "context >= 0" then "context" is used and the difference between If context >= 0 then context is used, and the difference between the
the Sample and its predicted value is encoded as is, else "-context" Sample and its predicted value is encoded as is; else -context is
is used and the difference between the Sample and its predicted value used, and the difference between the Sample and its predicted value
is encoded with a flipped sign. is encoded with a flipped sign.
3.6. Quantization Table Set Indexes 3.6. Quantization Table Set Indexes
For each Plane of each slice, a Quantization Table Set is selected For each Plane of each Slice, a Quantization Table Set is selected
from an index: from an index:
* For Y Plane, "quant_table_set_index[ 0 ]" index is used * For Y Plane, quant_table_set_index[ 0 ] index is used.
* For Cb and Cr Planes, "quant_table_set_index[ 1 ]" index is used * For Cb and Cr Planes, quant_table_set_index[ 1 ] index is used.
* For extra Plane, "quant_table_set_index[ (version <= 3 || * For extra Plane, quant_table_set_index[ (version <= 3 ||
chroma_planes) ? 2 : 1 ]" index is used chroma_planes) ? 2 : 1 ] index is used.
Background: in first implementations of FFV1 bitstream, the index for Background: in the first implementations of the FFV1 bitstream, the
Cb and Cr Planes was stored even if it is not used (chroma_planes set index for Cb and Cr Planes was stored even if it was not used
to 0), this index is kept for "version" <= 3 in order to keep (chroma_planes set to 0), this index is kept for version <= 3 in
compatibility with FFV1 bitstreams in the wild. order to keep compatibility with FFV1 bitstreams in the wild.
3.7. Color spaces 3.7. Color Spaces
FFV1 supports several color spaces. The count of allowed coded FFV1 supports several color spaces. The count of allowed coded
planes and the meaning of the extra Plane are determined by the Planes and the meaning of the extra Plane are determined by the
selected color space. selected color space.
The FFV1 bitstream interleaves data in an order determined by the The FFV1 bitstream interleaves data in an order determined by the
color space. In YCbCr for each Plane, each Line is coded from top to color space. In YCbCr for each Plane, each Line is coded from top to
bottom and for each Line, each Sample is coded from left to right. bottom, and for each Line, each Sample is coded from left to right.
In JPEG2000-RCT for each Line from top to bottom, each Plane is coded In JPEG 2000 RCT for each Line from top to bottom, each Plane is
and for each Plane, each Sample is encoded from left to right. coded, and for each Plane, each Sample is encoded from left to right.
3.7.1. YCbCr 3.7.1. YCbCr
This color space allows 1 to 4 Planes. This color space allows one to four Planes.
The Cb and Cr Planes are optional, but if used then MUST be used The Cb and Cr Planes are optional, but if they are used, then they
together. Omitting the Cb and Cr Planes codes the frames in MUST be used together. Omitting the Cb and Cr Planes codes the
grayscale without color data. frames in gray scale without color data.
An optional transparency Plane can be used to code transparency data. An optional transparency Plane can be used to code transparency data.
An FFV1 Frame using YCbCr MUST use one of the following arrangements: An FFV1 Frame using YCbCr MUST use one of the following arrangements:
* Y * Y
* Y, Transparency * Y, Transparency
* Y, Cb, Cr * Y, Cb, Cr
* Y, Cb, Cr, Transparency * Y, Cb, Cr, Transparency
The Y Plane MUST be coded first. If the Cb and Cr Planes are used The Y Plane MUST be coded first. If the Cb and Cr Planes are used,
then they MUST be coded after the Y Plane. If a transparency Plane then they MUST be coded after the Y Plane. If a transparency Plane
is used, then it MUST be coded last. is used, then it MUST be coded last.
3.7.2. RGB 3.7.2. RGB
This color space allows 3 or 4 Planes. This color space allows three or four Planes.
An optional transparency Plane can be used to code transparency data. An optional transparency Plane can be used to code transparency data.
JPEG2000-RCT is a Reversible Color Transform that codes RGB (red, JPEG 2000 RCT is a Reversible Color Transform that codes RGB (Red,
green, blue) Planes losslessly in a modified YCbCr color space Green, Blue) Planes losslessly in a modified YCbCr color space
[ISO.15444-1.2016]. Reversible Pixel transformations between YCbCr [ISO.15444-1.2019]. Reversible pixel transformations between YCbCr
and RGB use the following formulae. and RGB use the following formulae:
Cb = b - g Cb = b - g
Cr = r - g Cr = r - g
Y = g + (Cb + Cr) >> 2 Y = g + (Cb + Cr) >> 2
Figure 6: Description of the transformation of pixels from RGB Figure 6: Description of the transformation of pixels from RGB
color space to coded modified YCbCr color space. color space to coded, modified YCbCr color space.
g = Y - (Cb + Cr) >> 2 g = Y - (Cb + Cr) >> 2
r = Cr + g r = Cr + g
b = Cb + g b = Cb + g
Figure 7: Description of the transformation of pixels from coded Figure 7: Description of the transformation of pixels from coded,
modified YCbCr color space to RGB color space. modified YCbCr color space to RGB color space.
Cb and Cr are positively offset by "1 << bits_per_raw_sample" after Cb and Cr are positively offset by 1 << bits_per_raw_sample after the
the conversion from RGB to the modified YCbCr and are negatively conversion from RGB to the modified YCbCr, and they are negatively
offseted by the same value before the conversion from the modified offset by the same value before the conversion from the modified
YCbCr to RGB, in order to have only non-negative values after the YCbCr to RGB in order to have only nonnegative values after the
conversion. conversion.
When FFV1 uses the JPEG2000-RCT, the horizontal Lines are interleaved When FFV1 uses the JPEG 2000 RCT, the horizontal Lines are
to improve caching efficiency since it is most likely that the interleaved to improve caching efficiency since it is most likely
JPEG2000-RCT will immediately be converted to RGB during decoding. that the JPEG 2000 RCT will immediately be converted to RGB during
The interleaved coding order is also Y, then Cb, then Cr, and then, decoding. The interleaved coding order is also Y, then Cb, then Cr,
if used, transparency. and then, if used, transparency.
As an example, a Frame that is two Pixels wide and two Pixels high, As an example, a Frame that is two pixels wide and two pixels high
could comprise the following structure: could comprise the following structure:
+------------------------+------------------------+ +------------------------+------------------------+
| Pixel(1,1) | Pixel(2,1) | | Pixel(1,1) | Pixel(2,1) |
| Y(1,1) Cb(1,1) Cr(1,1) | Y(2,1) Cb(2,1) Cr(2,1) | | Y(1,1) Cb(1,1) Cr(1,1) | Y(2,1) Cb(2,1) Cr(2,1) |
+------------------------+------------------------+ +------------------------+------------------------+
| Pixel(1,2) | Pixel(2,2) | | Pixel(1,2) | Pixel(2,2) |
| Y(1,2) Cb(1,2) Cr(1,2) | Y(2,2) Cb(2,2) Cr(2,2) | | Y(1,2) Cb(1,2) Cr(1,2) | Y(2,2) Cb(2,2) Cr(2,2) |
+------------------------+------------------------+ +------------------------+------------------------+
In JPEG2000-RCT, the coding order would be left to right and then top In JPEG 2000 RCT, the coding order is left to right and then top to
to bottom, with values interleaved by Lines and stored in this order: bottom, with values interleaved by Lines and stored in this order:
Y(1,1) Y(2,1) Cb(1,1) Cb(2,1) Cr(1,1) Cr(2,1) Y(1,2) Y(2,2) Cb(1,2) Y(1,1) Y(2,1) Cb(1,1) Cb(2,1) Cr(1,1) Cr(2,1) Y(1,2) Y(2,2) Cb(1,2)
Cb(2,2) Cr(1,2) Cr(2,2) Cb(2,2) Cr(1,2) Cr(2,2)
3.7.2.1. Exception 3.7.2.1. RGB Exception
If "bits_per_raw_sample" is between 9 and 15 inclusive and If bits_per_raw_sample is between 9 and 15 inclusive and extra_plane
"extra_plane" is 0, the following formulae for reversible conversions is 0, the following formulae for reversible conversions between YCbCr
between YCbCr and RGB MUST be used instead of the ones above: and RGB MUST be used instead of the ones above:
Cb = g - b Cb = g - b
Cr = r - b Cr = r - b
Y = b + (Cb + Cr) >> 2 Y = b + (Cb + Cr) >> 2
Figure 8: Description of the transformation of pixels from RGB Figure 8: Description of the transformation of pixels from RGB
color space to coded modified YCbCr color space (in case of color space to coded, modified YCbCr color space (in case of
exception). exception).
b = Y - (Cb + Cr) >> 2 b = Y - (Cb + Cr) >> 2
r = Cr + b r = Cr + b
g = Cb + b g = Cb + b
Figure 9: Description of the transformation of pixels from coded Figure 9: Description of the transformation of pixels from coded,
modified YCbCr color space to RGB color space (in case of modified YCbCr color space to RGB color space (in case of
exception). exception).
Background: At the time of this writing, in all known implementations Background: At the time of this writing, in all known implementations
of FFV1 bitstream, when "bits_per_raw_sample" was between 9 and 15 of the FFV1 bitstream, when bits_per_raw_sample was between 9 and 15
inclusive and "extra_plane" is 0, GBR Planes were used as BGR Planes inclusive and extra_plane was 0, Green Blue Red (GBR) Planes were
during both encoding and decoding. In the meanwhile, 16-bit used as Blue Green Red (BGR) Planes during both encoding and
JPEG2000-RCT was implemented without this issue in one implementation decoding. Meanwhile, 16-bit JPEG 2000 RCT was implemented without
and validated by one conformance checker. Methods to address this this issue in one implementation and validated by one conformance
exception for the transform are under consideration for the next checker. Methods to address this exception for the transform are
version of the FFV1 bitstream. under consideration for the next version of the FFV1 bitstream.
3.8. Coding of the Sample Difference 3.8. Coding of the Sample Difference
Instead of coding the n+1 bits of the Sample Difference with Huffman Instead of coding the n+1 bits of the Sample Difference with Huffman
or Range coding (or n+2 bits, in the case of JPEG2000-RCT), only the or Range coding (or n+2 bits, in the case of JPEG 2000 RCT), only the
n (or n+1, in the case of JPEG2000-RCT) least significant bits are n (or n+1, in the case of JPEG 2000 RCT) least significant bits are
used, since this is sufficient to recover the original Sample. In used, since this is sufficient to recover the original Sample. In
the equation below, the term "bits" represents "bits_per_raw_sample + Figure 10, the term bits represents bits_per_raw_sample + 1 for JPEG
1" for JPEG2000-RCT or "bits_per_raw_sample" otherwise: 2000 RCT or bits_per_raw_sample otherwise:
coder_input = ((sample_difference + 2 ^ (bits - 1)) & coder_input = ((sample_difference + 2 ^ (bits - 1)) &
(2 ^ bits - 1)) - 2 ^ (bits - 1) (2 ^ bits - 1)) - 2 ^ (bits - 1)
Figure 10: Description of the coding of the Sample Difference in Figure 10: Description of the coding of the Sample Difference in
the bitstream. the bitstream.
3.8.1. Range Coding Mode 3.8.1. Range Coding Mode
Early experimental versions of FFV1 used the CABAC Arithmetic coder Early experimental versions of FFV1 used the CABAC Arithmetic coder
from H.264 as defined in [ISO.14496-10.2014] but due to the uncertain from H.264 as defined in [ISO.14496-10.2020], but due to the
patent/royalty situation, as well as its slightly worse performance, uncertain patent/royalty situation, as well as its slightly worse
CABAC was replaced by a Range coder based on an algorithm defined by performance, CABAC was replaced by a range coder based on an
G. Nigel N. Martin in 1979 [range-coding]. algorithm defined by G. Nigel N. Martin in 1979 [Range-Encoding].
3.8.1.1. Range Binary Values 3.8.1.1. Range Binary Values
To encode binary digits efficiently a Range coder is used. A Range To encode binary digits efficiently, a range coder is used. A range
coder encodes a series of binary symbols by using a probability coder encodes a series of binary symbols by using a probability
estimation within each context. The sizes of each of the 2 sub- estimation within each context. The sizes of each of the two
ranges are proportional to their estimated probability. The subranges are proportional to their estimated probability. The
quantization table is used to choose the context used from the Quantization Table is used to choose the context used from the
surrounding image sample values for the case of coding the sample surrounding image sample values for the case of coding the Sample
differences. Coding integers is done by coding multiple binary Differences. The coding of integers is done by coding multiple
values. The range decoder will read bytes until it can determine binary values. The range decoder will read bytes until it can
which sub-range the input falls into to return the next binary determine into which subrange the input falls to return the next
symbol. binary symbol.
To describe Range coding for FFV1 the following values are used: To describe Range coding for FFV1, the following values are used:
C_i the i-th Context. C_i the i-th context.
B_i the i-th byte of the bytestream. B_i the i-th byte of the bytestream.
R_i the Range at the i-th symbol. R_i the Range at the i-th symbol.
r_i the boundary between two sub-ranges of R_i: a sub-range of r_i r_i the boundary between two subranges of R_i: a subrange of r_i
values and a sub-range R_i - r_i values. values and a subrange R_i - r_i values.
L_i the Low value of the Range at the i-th symbol. L_i the Low value of the Range at the i-th symbol.
l_i a temporary variable to carry-over or adjust the Low value of l_i a temporary variable to carry over or adjust the Low value of
the Range between range coding operations. the Range between range coding operations.
t_i a temporary variable to transmit sub-ranges between range coding t_i a temporary variable to transmit subranges between range coding
operations. operations.
b_i the i-th Range coded binary value. b_i the i-th range-coded binary value.
S_(0, i) the i-th initial state. S_(0, i) the i-th initial state.
j_n the length of the bytestream encoding n binary symbols. j_n the length of the bytestream encoding n binary symbols.
The following Range coder state variables are initialized to the The following range coder state variables are initialized to the
following values. The Range is initialized to a value of 65,280 following values. The Range is initialized to a value of 65,280
(expressed in base 16 as 0xFF00) as depicted in Figure 11. The Low (expressed in base 16 as 0xFF00) as depicted in Figure 11. The Low
is initialized according to the value of the first two bytes as is initialized according to the value of the first two bytes as
depicted in Figure 12. j_i tracks the length of the bytestream depicted in Figure 12. j_i tracks the length of the bytestream
encoding while incremening from an initial value of j_0 to a final encoding while incrementing from an initial value of j_0 to a final
value of j_n. j_0 is initialized to 2 as depicted in Figure 13. value of j_n. j_0 is initialized to 2 as depicted in Figure 13.
R_(0) = 65280 R_(0) = 65280
Figure 11: The initial value for "Range". Figure 11: The initial value for the Range.
L_(0) = 2 ^ 8 * B_(0) + B_(1) L_(0) = 2 ^ 8 * B_(0) + B_(1)
Figure 12: The initial value for "Low" is set according to the Figure 12: The initial value for Low is set according to the
first two bytes of the bytestream. first two bytes of the bytestream.
j_(0) = 2 j_(0) = 2
Figure 13: The initial value for "j", the length of the Figure 13: The initial value for j, the length of the bytestream
bytestream encoding. encoding.
The following equations define how the Range coder variables evolve The following equations define how the range coder variables evolve
as it reads or writes symbols. as it reads or writes symbols.
r_(i) = floor( ( R_(i) * S_(i, C_(i)) ) / 2 ^ 8 ) r_(i) = floor( ( R_(i) * S_(i, C_(i)) ) / 2 ^ 8 )
Figure 14: This formula shows the positioning of range split Figure 14: This formula shows the positioning of range split
based on the State. based on the state.
b_(i) = 0 <==> b_(i) = 0 <==>
L_(i) < R_(i) - r_(i) ==> L_(i) < R_(i) - r_(i) ==>
S_(i + 1, C_(i)) = zero_state_(S_(i, C_(i))) AND S_(i + 1, C_(i)) = zero_state_(S_(i, C_(i))) AND
l_(i) = L_(i) AND l_(i) = L_(i) AND
t_(i) = R_(i) - r_(i) t_(i) = R_(i) - r_(i)
b_(i) = 1 <==> b_(i) = 1 <==>
L_(i) >= R_(i) - r_(i) ==> L_(i) >= R_(i) - r_(i) ==>
S_(i + 1, C_(i)) = one_state_(S_(i, C_(i))) AND S_(i + 1, C_(i)) = one_state_(S_(i, C_(i))) AND
l_(i) = L_(i) - R_(i) + r_(i) AND l_(i) = L_(i) - R_(i) + r_(i) AND
t_(i) = r_(i) t_(i) = r_(i)
Figure 15: This formula shows the linking of the decoded symbol Figure 15: This formula shows the linking of the decoded symbol
(represented as b_i), the updated State (represented as (represented as b_i), the updated state (represented as
S_(i+1,C_(i))), and the updated range (represented as a range S_(i+1,C_(i))), and the updated range (represented as a range
from l_i to t_i). from l_i to t_i).
C_(i) != k ==> S_(i + 1, k) = S_(i, k) C_(i) != k ==> S_(i + 1, k) = S_(i, k)
Figure 16: If the value of "k" is unequal to the i-th value of Figure 16: If the value of k is unequal to the i-th value of
Context, in other words if the State is unchanged from the last context, in other words, if the state is unchanged from the last
symbol coding, then the value of the State is carried over to the symbol coding, then the value of the state is carried over to the
next symbol coding. next symbol coding.
t_(i) < 2 ^ 8 ==> t_(i) < 2 ^ 8 ==>
R_(i + 1) = 2 ^ 8 * t_(i) AND R_(i + 1) = 2 ^ 8 * t_(i) AND
L_(i + 1) = 2 ^ 8 * l_(i) + B_(j_(i)) AND L_(i + 1) = 2 ^ 8 * l_(i) + B_(j_(i)) AND
j_(i + 1) = j_(i) + 1 j_(i + 1) = j_(i) + 1
t_(i) >= 2 ^ 8 ==> t_(i) >= 2 ^ 8 ==>
R_(i + 1) = t_(i) AND R_(i + 1) = t_(i) AND
L_(i + 1) = l_(i) AND L_(i + 1) = l_(i) AND
j_(i + 1) = j_(i) j_(i + 1) = j_(i)
Figure 17: This formula shows the linking of the Range coder with Figure 17: This formula shows the linking of the range coder with
the reading or writing of the bytestream. the reading or writing of the bytestream.
range = 0xFF00; range = 0xFF00;
end = 0; end = 0;
low = get_bits(16); low = get_bits(16);
if (low >= range) { if (low >= range) {
low = range; low = range;
end = 1; end = 1;
} }
Figure 18: A pseudo-code description of the initialization of Figure 18: A pseudocode description of the initialization of
Range coder variables in Range Binary mode. range coder variables in Range binary mode.
refill() { refill() {
if (range < 256) { if (range < 256) {
range = range * 256; range = range * 256;
low = low * 256; low = low * 256;
if (!end) { if (!end) {
c.low += get_bits(8); c.low += get_bits(8);
if (remaining_bits_in_bitstream( NumBytes ) == 0) { if (remaining_bits_in_bitstream( NumBytes ) == 0) {
end = 1; end = 1;
} }
} }
} }
} }
Figure 19: A pseudo-code description of refilling the Range Figure 19: A pseudocode description of refilling the binary value
Binary Value coder buffer. buffer of the range coder.
get_rac(state) { get_rac(state) {
rangeoff = (range * state) / 256; rangeoff = (range * state) / 256;
range -= rangeoff; range -= rangeoff;
if (low < range) { if (low < range) {
state = zero_state[state]; state = zero_state[state];
refill(); refill();
return 0; return 0;
} else { } else {
low -= range; low -= range;
state = one_state[state]; state = one_state[state];
range = rangeoff; range = rangeoff;
refill(); refill();
return 1; return 1;
} }
} }
Figure 20: A pseudo-code description of the read of a binary Figure 20: A pseudocode description of the read of a binary value
value in Range Binary mode. in Range binary mode.
3.8.1.1.1. Termination 3.8.1.1.1. Termination
The range coder can be used in three modes. The range coder can be used in three modes:
* In "Open mode" when decoding, every Symbol the reader attempts to * In Open mode when decoding, every symbol the reader attempts to
read is available. In this mode arbitrary data can have been read is available. In this mode, arbitrary data can have been
appended without affecting the range coder output. This mode is appended without affecting the range coder output. This mode is
not used in FFV1. not used in FFV1.
* In "Closed mode" the length in bytes of the bytestream is provided * In Closed mode, the length in bytes of the bytestream is provided
to the range decoder. Bytes beyond the length are read as 0 by to the range decoder. Bytes beyond the length are read as 0 by
the range decoder. This is generally one byte shorter than the the range decoder. This is generally one byte shorter than the
open mode. Open mode.
* In "Sentinel mode" the exact length in bytes is not known and thus * In Sentinel mode, the exact length in bytes is not known, and thus
the range decoder MAY read into the data that follows the range the range decoder MAY read into the data that follows the range-
coded bytestream by one byte. In "Sentinel mode", the end of the coded bytestream by one byte. In Sentinel mode, the end of the
range coded bytestream is a binary Symbol with state 129, which range-coded bytestream is a binary symbol with state 129, which
value SHALL be discarded. After reading this Symbol, the range value SHALL be discarded. After reading this symbol, the range
decoder will have read one byte beyond the end of the range coded decoder will have read one byte beyond the end of the range-coded
bytestream. This way the byte position of the end can be bytestream. This way the byte position of the end can be
determined. Bytestreams written in "Sentinel mode" can be read in determined. Bytestreams written in Sentinel mode can be read in
"Closed mode" if the length can be determined, in this case the Closed mode if the length can be determined. In this case, the
last (sentinel) Symbol will be read non-corrupted and be of value last (sentinel) symbol will be read uncorrupted and be of value 0.
0.
Above describes the range decoding. Encoding is defined as any The above describes the range decoding. Encoding is defined as any
process which produces a decodable bytestream. process that produces a decodable bytestream.
There are three places where range coder termination is needed in There are three places where range coder termination is needed in
FFV1. First is in the "Configuration Record", in this case the size FFV1. The first is in the Configuration Record, which in this case
of the range coded bytestream is known and handled as "Closed mode". the size of the range coded bytestream is known and handled as Closed
Second is the switch from the "Slice Header" which is range coded to mode. The second is the switch from the Slice Header, which is range
Golomb coded slices as "Sentinel mode". Third is the end of range coded to Golomb-coded Slices as Sentinel mode. The third is the end
coded Slices which need to terminate before the CRC at their end. of range-coded Slices, which need to terminate before the CRC at
This can be handled as "Sentinel mode" or as "Closed mode" if the CRC their end. This can be handled as Sentinel mode or as Closed mode if
position has been determined. the CRC position has been determined.
3.8.1.2. Range Non Binary Values 3.8.1.2. Range Non Binary Values
To encode scalar integers, it would be possible to encode each bit To encode scalar integers, it would be possible to encode each bit
separately and use the past bits as context. However that would mean separately and use the past bits as context. However, that would
255 contexts per 8-bit Symbol that is not only a waste of memory but mean 255 contexts per 8-bit symbol, which is not only a waste of
also requires more past data to reach a reasonably good estimate of memory but also requires more past data to reach a reasonably good
the probabilities. Alternatively assuming a Laplacian distribution estimate of the probabilities. Alternatively, it would also be
and only dealing with its variance and mean (as in Huffman coding) possible to assume a Laplacian distribution and only dealing with its
would also be possible, however, for maximum flexibility and variance and mean (as in Huffman coding). However, for maximum
simplicity, the chosen method uses a single Symbol to encode if a flexibility and simplicity, the chosen method uses a single symbol to
number is 0, and if not, encodes the number using its exponent, encode if a number is 0, and if the number is nonzero, it encodes the
mantissa and sign. The exact contexts used are best described by number using its exponent, mantissa, and sign. The exact contexts
Figure 21. used are best described by Figure 21.
int get_symbol(RangeCoder *c, uint8_t *state, int is_signed) { int get_symbol(RangeCoder *c, uint8_t *state, int is_signed) {
if (get_rac(c, state + 0) { if (get_rac(c, state + 0) {
return 0; return 0;
} }
int e = 0; int e = 0;
while (get_rac(c, state + 1 + min(e, 9)) { //1..10 while (get_rac(c, state + 1 + min(e, 9)) { //1..10
e++; e++;
} }
skipping to change at page 21, line 31 skipping to change at page 21, line 31
return a; return a;
} }
if (get_rac(c, state + 11 + min(e, 10))) { //11..21 if (get_rac(c, state + 11 + min(e, 10))) { //11..21
return -a; return -a;
} else { } else {
return a; return a;
} }
} }
Figure 21: A pseudo-code description of the contexts of Range Non Figure 21: A pseudocode description of the contexts of Range
Binary Values. nonbinary values.
"get_symbol" is used for the read out of "sample_difference" get_symbol is used for the read out of sample_difference indicated in
indicated in Figure 10. Figure 10.
"get_rac" returns a boolean, computed from the bytestream as get_rac returns a boolean, computed from the bytestream as described
described in Figure 14 as a formula and in Figure 20 as pseudo-code. by the formula found in Figure 14 and by the pseudocode found in
Figure 20.
3.8.1.3. Initial Values for the Context Model 3.8.1.3. Initial Values for the Context Model
When "keyframe" (see Section 4.4) value is 1, all Range coder state When the keyframe value (see Section 4.4) value is 1, all range coder
variables are set to their initial state. state variables are set to their initial state.
3.8.1.4. State Transition Table 3.8.1.4. State Transition Table
In this mode a State Transition Table is used, indicating in which In this model, a state transition table is used, indicating to which
state the decoder will move to, based on the current state and the state the decoder will move to, based on the current state and the
value extracted from Figure 20. value extracted from Figure 20.
one_state_(i) = one_state_(i) =
default_state_transition_(i) + state_transition_delta_(i) default_state_transition_(i) + state_transition_delta_(i)
Figure 22
Figure 22: Description of the coding of the state transition
table for a get_rac readout value of 0.
zero_state_(i) = 256 - one_state_(256-i) zero_state_(i) = 256 - one_state_(256-i)
Figure 23 Figure 23: Description of the coding of the state transition
table for a get_rac readout value of 1.
3.8.1.5. default_state_transition 3.8.1.5. default_state_transition
By default, the following State Transition Table is used: By default, the following state transition table is used:
0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27, 0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27,
28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42,
43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57,
58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73,
74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88,
skipping to change at page 23, line 5 skipping to change at page 22, line 52
180,181,182,183,184,185,186,187,188,189,190,190,191,192,194,194, 180,181,182,183,184,185,186,187,188,189,190,190,191,192,194,194,
195,196,197,198,199,200,201,202,202,204,205,206,207,208,209,209, 195,196,197,198,199,200,201,202,202,204,205,206,207,208,209,209,
210,211,212,213,215,215,216,217,218,219,220,220,222,223,224,225, 210,211,212,213,215,215,216,217,218,219,220,220,222,223,224,225,
226,227,227,229,229,230,231,232,234,234,235,236,237,238,239,240, 226,227,227,229,229,230,231,232,234,234,235,236,237,238,239,240,
241,242,243,244,245,246,247,248,248, 0, 0, 0, 0, 0, 0, 0, 241,242,243,244,245,246,247,248,248, 0, 0, 0, 0, 0, 0, 0,
Figure 24: Default state transition table for Range coding.
3.8.1.6. Alternative State Transition Table 3.8.1.6. Alternative State Transition Table
The alternative state transition table has been built using iterative The alternative state transition table has been built using iterative
minimization of frame sizes and generally performs better than the minimization of frame sizes and generally performs better than the
default. To use it, the "coder_type" (see Section 4.2.3) MUST be set default. To use it, the coder_type (see Section 4.2.3) MUST be set
to 2 and the difference to the default MUST be stored in the to 2, and the difference to the default MUST be stored in the
"Parameters", see Section 4.2. The reference implementation of FFV1 Parameters, see Section 4.2. At the time of this writing, the
in FFmpeg uses Figure 24 by default at the time of this writing when reference implementation of FFV1 in FFmpeg uses Figure 25 by default
Range coding is used. when Range coding is used.
0, 10, 10, 10, 10, 16, 16, 16, 28, 16, 16, 29, 42, 49, 20, 49, 0, 10, 10, 10, 10, 16, 16, 16, 28, 16, 16, 29, 42, 49, 20, 49,
59, 25, 26, 26, 27, 31, 33, 33, 33, 34, 34, 37, 67, 38, 39, 39, 59, 25, 26, 26, 27, 31, 33, 33, 33, 34, 34, 37, 67, 38, 39, 39,
40, 40, 41, 79, 43, 44, 45, 45, 48, 48, 64, 50, 51, 52, 88, 52, 40, 40, 41, 79, 43, 44, 45, 45, 48, 48, 64, 50, 51, 52, 88, 52,
53, 74, 55, 57, 58, 58, 74, 60,101, 61, 62, 84, 66, 66, 68, 69, 53, 74, 55, 57, 58, 58, 74, 60,101, 61, 62, 84, 66, 66, 68, 69,
87, 82, 71, 97, 73, 73, 82, 75,111, 77, 94, 78, 87, 81, 83, 97, 87, 82, 71, 97, 73, 73, 82, 75,111, 77, 94, 78, 87, 81, 83, 97,
skipping to change at page 23, line 47 skipping to change at page 23, line 47
175,189,179,181,186,183,192,185,200,187,191,188,190,197,193,196, 175,189,179,181,186,183,192,185,200,187,191,188,190,197,193,196,
197,194,195,196,198,202,199,201,210,203,207,204,205,206,208,214, 197,194,195,196,198,202,199,201,210,203,207,204,205,206,208,214,
209,211,221,212,213,215,224,216,217,218,219,220,222,228,223,225, 209,211,221,212,213,215,224,216,217,218,219,220,222,228,223,225,
226,224,227,229,240,230,231,232,233,234,235,236,238,239,237,242, 226,224,227,229,240,230,231,232,233,234,235,236,238,239,237,242,
241,243,242,244,245,246,247,248,249,250,251,252,252,253,254,255, 241,243,242,244,245,246,247,248,249,250,251,252,252,253,254,255,
Figure 24: Alternative state transition table for Range coding. Figure 25: Alternative state transition table for Range coding.
3.8.2. Golomb Rice Mode 3.8.2. Golomb Rice Mode
The end of the bitstream of the Frame is padded with 0-bits until the The end of the bitstream of the Frame is padded with zeroes until the
bitstream contains a multiple of 8 bits. bitstream contains a multiple of eight bits.
3.8.2.1. Signed Golomb Rice Codes 3.8.2.1. Signed Golomb Rice Codes
This coding mode uses Golomb Rice codes. The VLC is split into two This coding mode uses Golomb Rice codes. The VLC is split into two
parts. The prefix stores the most significant bits and the suffix parts: the prefix and suffix. The prefix stores the most significant
stores the k least significant bits or stores the whole number in the bits or indicates if the symbol is too large to be stored (this is
ESC case. known as the ESC case. The suffix either stores the k least
significant bits or stores the whole number in the ESC case.
int get_ur_golomb(k) { int get_ur_golomb(k) {
for (prefix = 0; prefix < 12; prefix++) { for (prefix = 0; prefix < 12; prefix++) {
if (get_bits(1)) { if (get_bits(1)) {
return get_bits(k) + (prefix << k); return get_bits(k) + (prefix << k);
} }
} }
return get_bits(bits) + 11; return get_bits(bits) + 11;
} }
Figure 25: A pseudo-code description of the read of an unsigned Figure 26: A pseudocode description of the read of an unsigned
integer in Golomb Rice mode. integer in Golomb Rice mode.
int get_sr_golomb(k) { int get_sr_golomb(k) {
v = get_ur_golomb(k); v = get_ur_golomb(k);
if (v & 1) return - (v >> 1) - 1; if (v & 1) return - (v >> 1) - 1;
else return (v >> 1); else return (v >> 1);
} }
Figure 26: A pseudo-code description of the read of a signed Figure 27: A pseudocode description of the read of a signed
integer in Golomb Rice mode. integer in Golomb Rice mode.
3.8.2.1.1. Prefix 3.8.2.1.1. Prefix
+================+=======+ +================+=======+
| bits | value | | bits | value |
+================+=======+ +================+=======+
| 1 | 0 | | 1 | 0 |
+----------------+-------+ +----------------+-------+
| 01 | 1 | | 01 | 1 |
skipping to change at page 25, line 24 skipping to change at page 25, line 4
| ... | ... | | ... | ... |
+----------------+-------+ +----------------+-------+
| 0000 0000 01 | 9 | | 0000 0000 01 | 9 |
+----------------+-------+ +----------------+-------+
| 0000 0000 001 | 10 | | 0000 0000 001 | 10 |
+----------------+-------+ +----------------+-------+
| 0000 0000 0001 | 11 | | 0000 0000 0001 | 11 |
+----------------+-------+ +----------------+-------+
| 0000 0000 0000 | ESC | | 0000 0000 0000 | ESC |
+----------------+-------+ +----------------+-------+
Table 1: Description
of the coding of the
prefix of signed
Golomb Rice codes.
Table 1 ESC is an ESCape symbol to indicate that the symbol to be stored is
"ESC" is an ESCape Symbol to indicate that the Symbol to be stored is
too large for normal storage and that an alternate storage method is too large for normal storage and that an alternate storage method is
used. used.
3.8.2.1.2. Suffix 3.8.2.1.2. Suffix
+=========+========================================+ +=========+========================================+
+=========+========================================+ +=========+========================================+
| non ESC | the k least significant bits MSB first | | non ESC | the k least significant bits MSB first |
+---------+----------------------------------------+ +---------+----------------------------------------+
| ESC | the value - 11, in MSB first order | | ESC | the value - 11, in MSB first order |
+---------+----------------------------------------+ +---------+----------------------------------------+
Table 2 Table 2: Description of the coding of the suffix
of signed Golomb Rice codes.
ESC MUST NOT be used if the value can be coded as non ESC. ESC MUST NOT be used if the value can be coded as non-ESC.
3.8.2.1.3. Examples 3.8.2.1.3. Examples
Table 3 shows practical examples of how Signed Golomb Rice Codes are Table 3 shows practical examples of how signed Golomb Rice codes are
decoded based on the series of bits extracted from the bitstream as decoded based on the series of bits extracted from the bitstream as
described by the method above: described by the method above:
+=====+=======================+=======+ +=====+=======================+=======+
| k | bits | value | | k | bits | value |
+=====+=======================+=======+ +=====+=======================+=======+
| 0 | 1 | 0 | | 0 | 1 | 0 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| 0 | 001 | 2 | | 0 | 001 | 2 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| 2 | 1 00 | 0 | | 2 | 1 00 | 0 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| 2 | 1 10 | 2 | | 2 | 1 10 | 2 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| 2 | 01 01 | 5 | | 2 | 01 01 | 5 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| any | 000000000000 10000000 | 139 | | any | 000000000000 10000000 | 139 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
Table 3: Examples of decoded Signed Table 3: Examples of decoded,
Golomb Rice Codes. signed Golomb Rice codes.
3.8.2.2. Run Mode 3.8.2.2. Run Mode
Run mode is entered when the context is 0 and left as soon as a non-0 Run mode is entered when the context is 0 and left as soon as a
difference is found. The sample difference is identical to the nonzero difference is found. The Sample Difference is identical to
predicted one. The run and the first different sample difference are the predicted one. The run and the first different Sample Difference
coded as defined in Section 3.8.2.4.1. are coded are coded as defined in Section 3.8.2.4.1.
3.8.2.2.1. Run Length Coding 3.8.2.2.1. Run Length Coding
The run value is encoded in two parts. The prefix part stores the The run value is encoded in two parts. The prefix part stores the
more significant part of the run as well as adjusting the "run_index" more significant part of the run as well as adjusting the run_index
that determines the number of bits in the less significant part of that determines the number of bits in the less significant part of
the run. The second part of the value stores the less significant the run. The second part of the value stores the less significant
part of the run as it is. The "run_index" is reset for each Plane part of the run as it is. The run_index is reset to zero for each
and slice to 0. Plane and Slice.
log2_run[41] = { log2_run[41] = {
0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1,
2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 3, 3, 3, 3,
4, 4, 5, 5, 6, 6, 7, 7, 4, 4, 5, 5, 6, 6, 7, 7,
8, 9,10,11,12,13,14,15, 8, 9,10,11,12,13,14,15,
16,17,18,19,20,21,22,23, 16,17,18,19,20,21,22,23,
24, 24,
}; };
skipping to change at page 27, line 33 skipping to change at page 26, line 49
} else { } else {
run_count = 0; run_count = 0;
} }
if (run_index) { if (run_index) {
run_index--; run_index--;
} }
run_mode = 2; run_mode = 2;
} }
} }
The "log2_run" array is also used within [ISO.14495-1.1999]. The log2_run array is also used within [ISO.14495-1.1999].
3.8.2.3. Sign extension 3.8.2.3. Sign Extension
"sign_extend" is the function of increasing the number of bits of an sign_extend is the function of increasing the number of bits of an
input binary number in twos complement signed number representation input binary number in two's complement signed number representation
while preserving the input number's sign (positive/negative) and while preserving the input number's sign (positive/negative) and
value, in order to fit in the output bit width. It MAY be computed value, in order to fit in the output bit width. It MAY be computed
with: with the following:
sign_extend(input_number, input_bits) { sign_extend(input_number, input_bits) {
negative_bias = 1 << (input_bits - 1); negative_bias = 1 << (input_bits - 1);
bits_mask = negative_bias - 1; bits_mask = negative_bias - 1;
output_number = input_number & bits_mask; // Remove negative bit output_number = input_number & bits_mask; // Remove negative bit
is_negative = input_number & negative_bias; // Test negative bit is_negative = input_number & negative_bias; // Test negative bit
if (is_negative) if (is_negative)
output_number -= negative_bias; output_number -= negative_bias;
return output_number return output_number
} }
skipping to change at page 29, line 10 skipping to change at page 29, line 5
3.8.2.4.1. Golomb Rice Sample Difference Coding 3.8.2.4.1. Golomb Rice Sample Difference Coding
Level coding is identical to the normal difference coding with the Level coding is identical to the normal difference coding with the
exception that the 0 value is removed as it cannot occur: exception that the 0 value is removed as it cannot occur:
diff = get_vlc_symbol(context_state); diff = get_vlc_symbol(context_state);
if (diff >= 0) { if (diff >= 0) {
diff++; diff++;
} }
Note, this is different from JPEG-LS, which doesn't use prediction in Note that this is different from JPEG-LS (lossless JPEG), which
run mode and uses a different encoding and context model for the last doesn't use prediction in run mode and uses a different encoding and
difference. On a small set of test Samples the use of prediction context model for the last difference. On a small set of test
slightly improved the compression rate. Samples, the use of prediction slightly improved the compression
rate.
3.8.2.5. Initial Values for the VLC context state 3.8.2.5. Initial Values for the VLC Context State
When "keyframe" (see Section 4.4) value is 1, all VLC coder state When keyframe (see Section 4.4) value is 1, all VLC coder state
variables are set to their initial state. variables are set to their initial state.
drift = 0; drift = 0;
error_sum = 4; error_sum = 4;
bias = 0; bias = 0;
count = 1; count = 1;
4. Bitstream 4. Bitstream
An FFV1 bitstream is composed of a series of one or more Frames and An FFV1 bitstream is composed of a series of one or more Frames and
(when required) a "Configuration Record". (when required) a Configuration Record.
Within the following sub-sections, pseudo-code is used, as described Within the following subsections, pseudocode as described in
in Section 2.2.1, to explain the structure of each FFV1 bitstream Section 2.2.1, is used to explain the structure of each FFV1
component. Table 4 lists symbols used to annotate that pseudo-code bitstream component. Table 4 lists symbols used to annotate that
in order to define the storage of the data referenced in that line of pseudocode in order to define the storage of the data referenced in
pseudo-code. that line of pseudocode.
+========+=================================================+ +========+==================================================+
| Symbol | Definition | | symbol | definition |
+========+=================================================+ +========+==================================================+
| u(n) | unsigned big endian integer Symbol using n bits | | u(n) | Unsigned, big-endian integer symbol using n bits |
+--------+-------------------------------------------------+ +--------+--------------------------------------------------+
| sg | Golomb Rice coded signed scalar Symbol coded | | br | Boolean (1-bit) symbol that is range coded with |
| | with the method described in Section 3.8.2 | | | the method described in Section 3.8.1.1 |
+--------+-------------------------------------------------+ +--------+--------------------------------------------------+
| br | Range coded Boolean (1-bit) Symbol with the | | ur | Unsigned scalar symbol that is range coded with |
| | method described in Section 3.8.1.1 | | | the method described in Section 3.8.1.2 |
+--------+-------------------------------------------------+ +--------+--------------------------------------------------+
| ur | Range coded unsigned scalar Symbol coded with | | sr | Signed scalar symbol that is range coded with |
| | the method described in Section 3.8.1.2 | | | the method described in Section 3.8.1.2 |
+--------+-------------------------------------------------+ +--------+--------------------------------------------------+
| sr | Range coded signed scalar Symbol coded with the | | sd | Sample difference symbol that is coded with the |
| | method described in Section 3.8.1.2 | | | method described in Section 3.8 |
+--------+-------------------------------------------------+ +--------+--------------------------------------------------+
| sd | Sample difference Symbol coded with the method |
| | described in Section 3.8 |
+--------+-------------------------------------------------+
Table 4: Definition of pseudo-code symbols for this Table 4: Definition of pseudocode symbols for this document.
document.
The following MUST be provided by external means during The following MUST be provided by external means during the
initialization of the decoder: initialization of the decoder:
"frame_pixel_width" is defined as Frame width in Pixels. frame_pixel_width is defined as Frame width in pixels.
"frame_pixel_height" is defined as Frame height in Pixels. frame_pixel_height is defined as Frame height in pixels.
Default values at the decoder initialization phase: Default values at the decoder initialization phase:
"ConfigurationRecordIsPresent" is set to 0. ConfigurationRecordIsPresent is set to 0.
4.1. Quantization Table Set 4.1. Quantization Table Set
The Quantization Table Sets are stored by storing the number of equal The Quantization Table Sets store a sequence of values that are equal
entries -1 of the first half of the table (represented as "len - 1" to one less than the count of equal concurrent entries for each set
in the pseudo-code below) using the method described in of equal concurrent entries within the first half of the table
Section 3.8.1.2. The second half doesn't need to be stored as it is (represented as <tt>len - 1</tt> in the pseudocode below) using the
identical to the first with flipped sign. "scale" and "len_count[ i method described in Section 3.8.1.2. The second half doesn’
][ j ]" are temporary values used for the computing of (U+2019)t need to be stored as it is identical to the first with
"context_count[ i ]" and are not used outside Quantization Table Set flipped sign. scale and len_count[ i ][ j ] are temporary values used
pseudo-code. for the computing of context_count[ i ] and are not used outside
Quantization Table Set pseudocode.
Example: Example:
Table: 0 0 1 1 1 1 2 2 -2 -2 -2 -1 -1 -1 -1 0 Table: 0 0 1 1 1 1 2 2 -2 -2 -2 -1 -1 -1 -1 0
Stored values: 1, 3, 1 Stored values: 1, 3, 1
"QuantizationTableSet" has its own initial states, all set to 128. QuantizationTableSet has its own initial states, all set to 128.
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
QuantizationTableSet( i ) { | QuantizationTableSet( i ) { |
scale = 1 | scale = 1 |
for (j = 0; j < MAX_CONTEXT_INPUTS; j++) { | for (j = 0; j < MAX_CONTEXT_INPUTS; j++) { |
QuantizationTable( i, j, scale ) | QuantizationTable( i, j, scale ) |
scale *= 2 * len_count[ i ][ j ] - 1 | scale *= 2 * len_count[ i ][ j ] - 1 |
} | } |
context_count[ i ] = ceil( scale / 2 ) | context_count[ i ] = ceil( scale / 2 ) |
} | } |
"MAX_CONTEXT_INPUTS" is 5. MAX_CONTEXT_INPUTS is 5.
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
QuantizationTable(i, j, scale) { | QuantizationTable(i, j, scale) { |
v = 0 | v = 0 |
for (k = 0; k < 128;) { | for (k = 0; k < 128;) { |
len - 1 | ur len - 1 | ur
for (n = 0; n < len; n++) { | for (n = 0; n < len; n++) { |
quant_tables[ i ][ j ][ k ] = scale * v | quant_tables[ i ][ j ][ k ] = scale * v |
k++ | k++ |
} | } |
v++ | v++ |
skipping to change at page 31, line 47 skipping to change at page 31, line 28
quant_tables[ i ][ j ][ 256 - k ] = \ | quant_tables[ i ][ j ][ 256 - k ] = \ |
-quant_tables[ i ][ j ][ k ] | -quant_tables[ i ][ j ][ k ] |
} | } |
quant_tables[ i ][ j ][ 128 ] = \ | quant_tables[ i ][ j ][ 128 ] = \ |
-quant_tables[ i ][ j ][ 127 ] | -quant_tables[ i ][ j ][ 127 ] |
len_count[ i ][ j ] = v | len_count[ i ][ j ] = v |
} | } |
4.1.1. quant_tables 4.1.1. quant_tables
"quant_tables[ i ][ j ][ k ]" indicates the quantization table value quant_tables[ i ][ j ][ k ] indicates the quantization table value of
of the Quantized Sample Difference "k" of the Quantization Table "j" the Quantized Sample Difference k of the Quantization Table j of the
of the Quantization Table Set "i". Quantization Table Set i.
4.1.2. context_count 4.1.2. context_count
"context_count[ i ]" indicates the count of contexts for Quantization context_count[ i ] indicates the count of contexts for Quantization
Table Set "i". "context_count[ i ]" MUST be less than or equal to Table Set i. context_count[ i ] MUST be less than or equal to 32768.
32768.
4.2. Parameters 4.2. Parameters
The "Parameters" section contains significant characteristics about The Parameters section contains significant characteristics about the
the decoding configuration used for all instances of Frame (in FFV1 decoding configuration used for all instances of Frame (in FFV1
version 0 and 1) or the whole FFV1 bitstream (other versions), version 0 and 1) or the whole FFV1 bitstream (other versions),
including the stream version, color configuration, and quantization including the stream version, color configuration, and quantization
tables. Figure 27 describes the contents of the bitstream. tables. Figure 28 describes the contents of the bitstream.
"Parameters" has its own initial states, all set to 128. Parameters has its own initial states, all set to 128.
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Parameters( ) { | Parameters( ) { |
version | ur version | ur
if (version >= 3) { | if (version >= 3) { |
micro_version | ur micro_version | ur
} | } |
coder_type | ur coder_type | ur
if (coder_type > 1) { | if (coder_type > 1) { |
for (i = 1; i < 256; i++) { | for (i = 1; i < 256; i++) { |
state_transition_delta[ i ] | sr state_transition_delta[ i ] | sr
skipping to change at page 33, line 50 skipping to change at page 32, line 50
initial_state_delta[ i ][ j ][ k ] | sr initial_state_delta[ i ][ j ][ k ] | sr
} | } |
} | } |
} | } |
} | } |
ec | ur ec | ur
intra | ur intra | ur
} | } |
} | } |
Figure 27: A pseudo-code description of the bitstream contents. Figure 28: A pseudocode description of the bitstream contents.
CONTEXT_SIZE is 32. CONTEXT_SIZE is 32.
4.2.1. version 4.2.1. version
"version" specifies the version of the FFV1 bitstream. version specifies the version of the FFV1 bitstream.
Each version is incompatible with other versions: decoders SHOULD Each version is incompatible with other versions: decoders SHOULD
reject FFV1 bitstreams due to an unknown version. reject FFV1 bitstreams due to an unknown version.
Decoders SHOULD reject FFV1 bitstreams with version <= 1 && Decoders SHOULD reject FFV1 bitstreams with version <= 1 &&
ConfigurationRecordIsPresent == 1. ConfigurationRecordIsPresent == 1.
Decoders SHOULD reject FFV1 bitstreams with version >= 3 && Decoders SHOULD reject FFV1 bitstreams with version >= 3 &&
ConfigurationRecordIsPresent == 0. ConfigurationRecordIsPresent == 0.
skipping to change at page 34, line 34 skipping to change at page 33, line 34
+-------+-------------------------+ +-------+-------------------------+
| 2 | reserved* | | 2 | reserved* |
+-------+-------------------------+ +-------+-------------------------+
| 3 | FFV1 version 3 | | 3 | FFV1 version 3 |
+-------+-------------------------+ +-------+-------------------------+
| 4 | FFV1 version 4 | | 4 | FFV1 version 4 |
+-------+-------------------------+ +-------+-------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------+ +-------+-------------------------+
Table 5 Table 5: The definitions for
version values.
* Version 2 was experimental and this document does not describe it. * Version 2 was experimental and this document does not describe it.
4.2.2. micro_version 4.2.2. micro_version
"micro_version" specifies the micro-version of the FFV1 bitstream. micro_version specifies the micro-version of the FFV1 bitstream.
After a version is considered stable (a micro-version value is After a version is considered stable (a micro-version value is
assigned to be the first stable variant of a specific version), each assigned to be the first stable variant of a specific version), each
new micro-version after this first stable variant is compatible with new micro-version after this first stable variant is compatible with
the previous micro-version: decoders SHOULD NOT reject FFV1 the previous micro-version: decoders SHOULD NOT reject FFV1
bitstreams due to an unknown micro-version equal or above the micro- bitstreams due to an unknown micro-version equal or above the micro-
version considered as stable. version considered as stable.
Meaning of "micro_version" for "version" 3: Meaning of micro_version for version 3:
+=======+=========================+ +=======+=========================+
| value | micro_version | | value | micro_version |
+=======+=========================+ +=======+=========================+
| 0...3 | reserved* | | 0...3 | reserved* |
+-------+-------------------------+ +-------+-------------------------+
| 4 | first stable variant | | 4 | first stable variant |
+-------+-------------------------+ +-------+-------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------+ +-------+-------------------------+
Table 6: The definitions for Table 6: The definitions for
"micro_version" values for FFV1 micro_version values for FFV1
version 3. version 3.
* development versions may be incompatible with the stable variants. * Development versions may be incompatible with the stable variants.
Meaning of "micro_version" for "version" 4 (note: at the time of Meaning of micro_version for version 4 (note: at the time of writing
writing of this specification, version 4 is not considered stable so of this specification, version 4 is not considered stable so the
the first stable "micro_version" value is to be announced in the first stable micro_version value is to be announced in the future):
future):
+=========+=========================+ +=========+=========================+
| value | micro_version | | value | micro_version |
+=========+=========================+ +=========+=========================+
| 0...TBA | reserved* | | 0...TBA | reserved* |
+---------+-------------------------+ +---------+-------------------------+
| TBA | first stable variant | | TBA | first stable variant |
+---------+-------------------------+ +---------+-------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+---------+-------------------------+ +---------+-------------------------+
Table 7: The definitions for Table 7: The definitions for
"micro_version" values for FFV1 micro_version values for FFV1
version 4. version 4.
* development versions which may be incompatible with the stable * Development versions which may be incompatible with the stable
variants. variants.
4.2.3. coder_type 4.2.3. coder_type
"coder_type" specifies the coder used. coder_type specifies the coder used.
+=======+=================================================+ +=======+=================================================+
| value | coder used | | value | coder used |
+=======+=================================================+ +=======+=================================================+
| 0 | Golomb Rice | | 0 | Golomb Rice |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| 1 | Range Coder with default state transition table | | 1 | Range coder with default state transition table |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| 2 | Range Coder with custom state transition table | | 2 | Range coder with custom state transition table |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
Table 8 Table 8: The definitions for coder_type values.
Restrictions: Restrictions:
If "coder_type" is 0, then "bits_per_raw_sample" SHOULD NOT be > 8. If coder_type is 0, then bits_per_raw_sample SHOULD NOT be > 8.
Background: At the time of this writing, there is no known Background: At the time of this writing, there is no known
implementation of FFV1 bitstream supporting Golomb Rice algorithm implementation of FFV1 bitstream supporting the Golomb Rice algorithm
with "bits_per_raw_sample" greater than 8, and Range Coder is with bits_per_raw_sample greater than eight, and range coder is
prefered. preferred.
4.2.4. state_transition_delta 4.2.4. state_transition_delta
"state_transition_delta" specifies the Range coder custom state state_transition_delta specifies the range coder custom state
transition table. transition table.
If "state_transition_delta" is not present in the FFV1 bitstream, all If state_transition_delta is not present in the FFV1 bitstream, all
Range coder custom state transition table elements are assumed to be range coder custom state transition table elements are assumed to be
0. 0.
4.2.5. colorspace_type 4.2.5. colorspace_type
"colorspace_type" specifies the color space encoded, the pixel colorspace_type specifies the color space encoded, the pixel
transformation used by the encoder, the extra plane content, as well transformation used by the encoder, the extra Plane content, as well
as interleave method. as interleave method.
+=======+==============+================+==============+============+ +=======+==============+================+==============+============+
| value | color space | pixel | extra plane | interleave | | value | color space | pixel | extra Plane | interleave |
| | encoded | transformation | content | method | | | encoded | transformation | content | method |
+=======+==============+================+==============+============+ +=======+==============+================+==============+============+
| 0 | YCbCr | None | Transparency | Plane then | | 0 | YCbCr | None | Transparency | Plane then |
| | | | | Line | | | | | | Line |
+-------+--------------+----------------+--------------+------------+ +-------+--------------+----------------+--------------+------------+
| 1 | RGB | JPEG2000-RCT | Transparency | Line then | | 1 | RGB | JPEG 2000 RCT | Transparency | Line then |
| | | | | Plane | | | | | | Plane |
+-------+--------------+----------------+--------------+------------+ +-------+--------------+----------------+--------------+------------+
| Other | reserved | reserved for | reserved for | reserved | | Other | reserved | reserved for | reserved for | reserved |
| | for future | future use | future use | for future | | | for future | future use | future use | for future |
| | use | | | use | | | use | | | use |
+-------+--------------+----------------+--------------+------------+ +-------+--------------+----------------+--------------+------------+
Table 9 Table 9: The definitions for colorspace_type values.
FFV1 bitstreams with "colorspace_type" == 1 && ("chroma_planes" != FFV1 bitstreams with colorspace_type == 1 && (chroma_planes != 1 ||
1 || "log2_h_chroma_subsample" != 0 || "log2_v_chroma_subsample" != log2_h_chroma_subsample != 0 || log2_v_chroma_subsample != 0) are not
0) are not part of this specification. part of this specification.
4.2.6. chroma_planes 4.2.6. chroma_planes
"chroma_planes" indicates if chroma (color) Planes are present. chroma_planes indicates if chroma (color) Planes are present.
+=======+===============================+ +=======+===============================+
| value | presence | | value | presence |
+=======+===============================+ +=======+===============================+
| 0 | chroma Planes are not present | | 0 | chroma Planes are not present |
+-------+-------------------------------+ +-------+-------------------------------+
| 1 | chroma Planes are present | | 1 | chroma Planes are present |
+-------+-------------------------------+ +-------+-------------------------------+
Table 10 Table 10: The definitions for
chroma_planes values.
4.2.7. bits_per_raw_sample 4.2.7. bits_per_raw_sample
"bits_per_raw_sample" indicates the number of bits for each Sample. bits_per_raw_sample indicates the number of bits for each Sample.
Inferred to be 8 if not present. Inferred to be 8 if not present.
+=======+=================================+ +=======+=================================+
| value | bits for each sample | | value | bits for each sample |
+=======+=================================+ +=======+=================================+
| 0 | reserved* | | 0 | reserved* |
+-------+---------------------------------+ +-------+---------------------------------+
| Other | the actual bits for each Sample | | Other | the actual bits for each Sample |
+-------+---------------------------------+ +-------+---------------------------------+
Table 11 Table 11: The definitions for
bits_per_raw_sample values.
* Encoders MUST NOT store "bits_per_raw_sample" = 0. Decoders SHOULD * Encoders MUST NOT store bits_per_raw_sample = 0. Decoders SHOULD
accept and interpret "bits_per_raw_sample" = 0 as 8. accept and interpret bits_per_raw_sample = 0 as 8.
4.2.8. log2_h_chroma_subsample 4.2.8. log2_h_chroma_subsample
"log2_h_chroma_subsample" indicates the subsample factor, stored in log2_h_chroma_subsample indicates the subsample factor, stored in
powers to which the number 2 is raised, between luma and chroma width powers to which the number 2 is raised, between luma and chroma width
("chroma_width = 2 ^ -log2_h_chroma_subsample * luma_width"). (chroma_width = 2 ^ -log2_h_chroma_subsample * luma_width).
4.2.9. log2_v_chroma_subsample 4.2.9. log2_v_chroma_subsample
"log2_v_chroma_subsample" indicates the subsample factor, stored in log2_v_chroma_subsample indicates the subsample factor, stored in
powers to which the number 2 is raised, between luma and chroma powers to which the number 2 is raised, between luma and chroma
height ("chroma_height = 2 ^ -log2_v_chroma_subsample * height (chroma_height = 2 ^ -log2_v_chroma_subsample * luma_height).
luma_height").
4.2.10. extra_plane 4.2.10. extra_plane
"extra_plane" indicates if an extra Plane is present. extra_plane indicates if an extra Plane is present.
+=======+============================+ +=======+============================+
| value | presence | | value | presence |
+=======+============================+ +=======+============================+
| 0 | extra Plane is not present | | 0 | extra Plane is not present |
+-------+----------------------------+ +-------+----------------------------+
| 1 | extra Plane is present | | 1 | extra Plane is present |
+-------+----------------------------+ +-------+----------------------------+
Table 12 Table 12: The definitions for
extra_plane values.
4.2.11. num_h_slices 4.2.11. num_h_slices
"num_h_slices" indicates the number of horizontal elements of the num_h_slices indicates the number of horizontal elements of the Slice
slice raster. raster.
Inferred to be 1 if not present. Inferred to be 1 if not present.
4.2.12. num_v_slices 4.2.12. num_v_slices
"num_v_slices" indicates the number of vertical elements of the slice num_v_slices indicates the number of vertical elements of the Slice
raster. raster.
Inferred to be 1 if not present. Inferred to be 1 if not present.
4.2.13. quant_table_set_count 4.2.13. quant_table_set_count
"quant_table_set_count" indicates the number of Quantization quant_table_set_count indicates the number of Quantization
Table Sets. "quant_table_set_count" MUST be less than or equal to 8. Table Sets. quant_table_set_count MUST be less than or equal to 8.
Inferred to be 1 if not present. Inferred to be 1 if not present.
MUST NOT be 0. MUST NOT be 0.
4.2.14. states_coded 4.2.14. states_coded
"states_coded" indicates if the respective Quantization Table Set has states_coded indicates if the respective Quantization Table Set has
the initial states coded. the initial states coded.
Inferred to be 0 if not present. Inferred to be 0 if not present.
+=======+================================+ +=======+================================+
| value | initial states | | value | initial states |
+=======+================================+ +=======+================================+
| 0 | initial states are not present | | 0 | initial states are not present |
| | and are assumed to be all 128 | | | and are assumed to be all 128 |
+-------+--------------------------------+ +-------+--------------------------------+
| 1 | initial states are present | | 1 | initial states are present |
+-------+--------------------------------+ +-------+--------------------------------+
Table 13 Table 13: The definitions for
states_coded values.
4.2.15. initial_state_delta 4.2.15. initial_state_delta
"initial_state_delta[ i ][ j ][ k ]" indicates the initial Range initial_state_delta[ i ][ j ][ k ] indicates the initial range coder
coder state, it is encoded using "k" as context index and state, and it is encoded using k as context index for the range coder
and the following pseudocode:
pred = j ? initial_states[ i ][j - 1][ k ] : 128 pred = j ? initial_states[ i ][j - 1][ k ] : 128
Figure 28 Figure 29: Predictor value for the coding of initial_state_delta[
i ][ j ][ k ].
initial_state[ i ][ j ][ k ] = initial_state[ i ][ j ][ k ] =
( pred + initial_state_delta[ i ][ j ][ k ] ) & 255 ( pred + initial_state_delta[ i ][ j ][ k ] ) & 255
Figure 29 Figure 30: Description of the coding of initial_state_delta[ i ][
j ][ k ].
4.2.16. ec 4.2.16. ec
"ec" indicates the error detection/correction type. ec indicates the error detection/correction type.
+=======+=================================================+ +=======+=============================================+
| value | error detection/correction type | | value | error detection/correction type |
+=======+=================================================+ +=======+=============================================+
| 0 | 32-bit CRC in "ConfigurationRecord" | | 0 | 32-bit CRC in ConfigurationRecord |
+-------+-------------------------------------------------+ +-------+---------------------------------------------+
| 1 | 32-bit CRC in "Slice" and "ConfigurationRecord" | | 1 | 32-bit CRC in Slice and ConfigurationRecord |
+-------+-------------------------------------------------+ +-------+---------------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------------------------------+ +-------+---------------------------------------------+
Table 14 Table 14: The definitions for ec values.
4.2.17. intra 4.2.17. intra
"intra" indicates the constraint on "keyframe" in each instance of intra indicates the constraint on keyframe in each instance of Frame.
Frame.
Inferred to be 0 if not present. Inferred to be 0 if not present.
+=======+=======================================================+ +=======+=====================================================+
| value | relationship | | value | relationship |
+=======+=======================================================+ +=======+=====================================================+
| 0 | "keyframe" can be 0 or 1 (non keyframes or keyframes) | | 0 | keyframe can be 0 or 1 (non keyframes or keyframes) |
+-------+-------------------------------------------------------+ +-------+-----------------------------------------------------+
| 1 | "keyframe" MUST be 1 (keyframes only) | | 1 | keyframeMUST be 1 (keyframes only) |
+-------+-------------------------------------------------------+ +-------+-----------------------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------------------------------------+ +-------+-----------------------------------------------------+
Table 15 Table 15: The definitions for intra values.
4.3. Configuration Record 4.3. Configuration Record
In the case of a FFV1 bitstream with "version >= 3", a "Configuration In the case of a FFV1 bitstream with version >= 3, a Configuration
Record" is stored in the underlying Container as described in Record is stored in the underlying container as described in
Section 4.3.3. It contains the "Parameters" used for all instances Section 4.3.3. It contains the Parameters used for all instances of
of Frame. The size of the "Configuration Record", "NumBytes", is Frame. The size of the Configuration Record, NumBytes, is supplied
supplied by the underlying Container. by the underlying container.
pseudo-code | type pseudocode | type
-----------------------------------------------------------|----- -----------------------------------------------------------|-----
ConfigurationRecord( NumBytes ) { | ConfigurationRecord( NumBytes ) { |
ConfigurationRecordIsPresent = 1 | ConfigurationRecordIsPresent = 1 |
Parameters( ) | Parameters( ) |
while (remaining_symbols_in_syntax(NumBytes - 4)) { | while (remaining_symbols_in_syntax(NumBytes - 4)) { |
reserved_for_future_use | br/ur/sr reserved_for_future_use | br/ur/sr
} | } |
configuration_record_crc_parity | u(32) configuration_record_crc_parity | u(32)
} | } |
4.3.1. reserved_for_future_use 4.3.1. reserved_for_future_use
"reserved_for_future_use" is a placeholder for future updates of this reserved_for_future_use is a placeholder for future updates of this
specification. specification.
Encoders conforming to this version of this specification SHALL NOT Encoders conforming to this version of this specification SHALL NOT
write "reserved_for_future_use". write reserved_for_future_use.
Decoders conforming to this version of this specification SHALL Decoders conforming to this version of this specification SHALL
ignore "reserved_for_future_use". ignore reserved_for_future_use.
4.3.2. configuration_record_crc_parity 4.3.2. configuration_record_crc_parity
"configuration_record_crc_parity" 32 bits that are chosen so that the configuration_record_crc_parity is 32 bits that are chosen so that
"Configuration Record" as a whole has a CRC remainder of 0. the Configuration Record as a whole has a CRC remainder of zero.
This is equivalent to storing the CRC remainder in the 32-bit parity. This is equivalent to storing the CRC remainder in the 32-bit parity.
The CRC generator polynomial used is described in Section 4.9.3. The CRC generator polynomial used is described in Section 4.9.3.
4.3.3. Mapping FFV1 into Containers 4.3.3. Mapping FFV1 into Containers
This "Configuration Record" can be placed in any file format This Configuration Record can be placed in any file format that
supporting "Configuration Records", fitting as much as possible with supports Configuration Records, fitting as much as possible with how
how the file format uses to store "Configuration Records". The the file format stores Configuration Records. The Configuration
"Configuration Record" storage place and "NumBytes" are currently Record storage place and NumBytes are currently defined and supported
defined and supported by this version of this specification for the for the following formats:
following formats:
4.3.3.1. AVI File Format 4.3.3.1. Audio Video Interleave (AVI) File Format
The "Configuration Record" extends the stream format chunk ("AVI ", The Configuration Record extends the stream format chunk ("AVI ",
"hdlr", "strl", "strf") with the ConfigurationRecord bitstream. "hdlr", "strl", "strf") with the ConfigurationRecord bitstream.
See [AVI] for more information about chunks. See [AVI] for more information about chunks.
"NumBytes" is defined as the size, in bytes, of the strf chunk NumBytes is defined as the size, in bytes, of the "strf" chunk
indicated in the chunk header minus the size of the stream format indicated in the chunk header minus the size of the stream format
structure. structure.
4.3.3.2. ISO Base Media File Format 4.3.3.2. ISO Base Media File Format
The "Configuration Record" extends the sample description box The Configuration Record extends the sample description box ("moov",
("moov", "trak", "mdia", "minf", "stbl", "stsd") with a "glbl" box "trak", "mdia", "minf", "stbl", "stsd") with a "glbl" box that
that contains the ConfigurationRecord bitstream. See contains the ConfigurationRecord bitstream. See [ISO.14496-12.2020]
[ISO.14496-12.2015] for more information about boxes. for more information about boxes.
"NumBytes" is defined as the size, in bytes, of the "glbl" box NumBytes is defined as the size, in bytes, of the "glbl" box
indicated in the box header minus the size of the box header. indicated in the box header minus the size of the box header.
4.3.3.3. NUT File Format 4.3.3.3. NUT File Format
The "codec_specific_data" element (in "stream_header" packet) The codec_specific_data element (in stream_header packet) contains
contains the ConfigurationRecord bitstream. See [NUT] for more the ConfigurationRecord bitstream. See [NUT] for more information
information about elements. about elements.
"NumBytes" is defined as the size, in bytes, of the NumBytes is defined as the size, in bytes, of the codec_specific_data
"codec_specific_data" element as indicated in the "length" field of element as indicated in the "length" field of codec_specific_data.
"codec_specific_data".
4.3.3.4. Matroska File Format 4.3.3.4. Matroska File Format
FFV1 SHOULD use "V_FFV1" as the Matroska "Codec ID". For FFV1 FFV1 SHOULD use V_FFV1 as the Matroska Codec ID. For FFV1 versions 2
versions 2 or less, the Matroska "CodecPrivate" Element SHOULD NOT be or less, the Matroska CodecPrivate Element SHOULD NOT be used. For
used. For FFV1 versions 3 or greater, the Matroska "CodecPrivate" FFV1 versions 3 or greater, the Matroska CodecPrivate Element MUST
Element MUST contain the FFV1 "Configuration Record" structure and no contain the FFV1 Configuration Record structure and no other data.
other data. See [Matroska] for more information about elements. See [I-D.ietf-cellar-matroska] for more information about elements.
"NumBytes" is defined as the "Element Data Size" of the NumBytes is defined as the Element Data Size of the CodecPrivate
"CodecPrivate" Element. Element.
4.4. Frame 4.4. Frame
A Frame is an encoded representation of a complete static image. The A Frame is an encoded representation of a complete static image. The
whole Frame is provided by the underlaying container. whole Frame is provided by the underlaying container.
A Frame consists of the "keyframe" field, "Parameters" (if "version" A Frame consists of the keyframe field, Parameters (if version <= 1),
<= 1), and a sequence of independent slices. The pseudo-code below and a sequence of independent Slices. The pseudocode below describes
describes the contents of a Frame. the contents of a Frame.
"keyframe" field has its own initial state, set to 128. The keyframe field has its own initial state, set to 128.
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Frame( NumBytes ) { | Frame( NumBytes ) { |
keyframe | br keyframe | br
if (keyframe && !ConfigurationRecordIsPresent { | if (keyframe && !ConfigurationRecordIsPresent { |
Parameters( ) | Parameters( ) |
} | } |
while (remaining_bits_in_bitstream( NumBytes )) { | while (remaining_bits_in_bitstream( NumBytes )) { |
Slice( ) | Slice( ) |
} | } |
} | } |
Architecture overview of slices in a Frame: The following is an architecture overview of Slices in a Frame:
+=================================================================+
+=================================================================+
| first slice header |
+-----------------------------------------------------------------+
| first slice content |
+-----------------------------------------------------------------+
| first slice footer |
+-----------------------------------------------------------------+
| --------------------------------------------------------------- |
+-----------------------------------------------------------------+
| second slice header |
+-----------------------------------------------------------------+
| second slice content |
+-----------------------------------------------------------------+
| second slice footer |
+-----------------------------------------------------------------+
| --------------------------------------------------------------- |
+-----------------------------------------------------------------+
| ... |
+-----------------------------------------------------------------+
| --------------------------------------------------------------- |
+-----------------------------------------------------------------+
| last slice header |
+-----------------------------------------------------------------+
| last slice content |
+-----------------------------------------------------------------+
| last slice footer |
+-----------------------------------------------------------------+
Table 16 +-----------------------------------------------------------------+ |
first Slice header |
+-----------------------------------------------------------------+ |
first Slice content |
+-----------------------------------------------------------------+ |
first Slice footer | +-----------------------------------------------
------------------+ |------------------------------------------------
---------------|
+-----------------------------------------------------------------+ |
second Slice header |
+-----------------------------------------------------------------+ |
second Slice content |
+-----------------------------------------------------------------+ |
second Slice footer | +----------------------------------------------
-------------------+ |-----------------------------------------------
----------------|
+-----------------------------------------------------------------+ |
... | +-------------------------------------------------------------
----+ |--------------------------------------------------------------
-|
+-----------------------------------------------------------------+ |
last Slice header |
+-----------------------------------------------------------------+ |
last Slice content |
+-----------------------------------------------------------------+ |
last Slice footer |
+-----------------------------------------------------------------+
4.5. Slice 4.5. Slice
A "Slice" is an independent spatial sub-section of a Frame that is A Slice is an independent, spatial subsection of a Frame that is
encoded separately from another region of the same Frame. The use of encoded separately from another region of the same Frame. The use of
more than one "Slice" per Frame can be useful for taking advantage of more than one Slice per Frame provides opportunities for taking
the opportunities of multithreaded encoding and decoding. advantage of multithreaded encoding and decoding.
A "Slice" consists of a "Slice Header" (when relevant), a "Slice A Slice consists of a Slice Header (when relevant), a Slice Content,
Content", and a "Slice Footer" (when relevant). The pseudo-code and a Slice Footer (when relevant). The pseudocode below describes
below describes the contents of a "Slice". the contents of a Slice.
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Slice( ) { | Slice( ) { |
if (version >= 3) { | if (version >= 3) { |
SliceHeader( ) | SliceHeader( ) |
} | } |
SliceContent( ) | SliceContent( ) |
if (coder_type == 0) { | if (coder_type == 0) { |
while (!byte_aligned()) { | while (!byte_aligned()) { |
padding | u(1) padding | u(1)
} | } |
skipping to change at page 44, line 38 skipping to change at page 43, line 31
if (version <= 1) { | if (version <= 1) { |
while (remaining_bits_in_bitstream( NumBytes ) != 0) {| while (remaining_bits_in_bitstream( NumBytes ) != 0) {|
reserved | u(1) reserved | u(1)
} | } |
} | } |
if (version >= 3) { | if (version >= 3) { |
SliceFooter( ) | SliceFooter( ) |
} | } |
} | } |
"padding" specifies a bit without any significance and used only for padding specifies a bit without any significance and used only for
byte alignment. MUST be 0. byte alignment. padding MUST be 0.
"reserved" specifies a bit without any significance in this revision reserved specifies a bit without any significance in this
of the specification and may have a significance in a later revision specification but may have a significance in a later revision of this
of this specification. specification.
Encoders SHOULD NOT fill "reserved". Encoders SHOULD NOT fill reserved.
Decoders SHOULD ignore "reserved". Decoders SHOULD ignore reserved.
4.6. Slice Header 4.6. Slice Header
A "Slice Header" provides information about the decoding A Slice Header provides information about the decoding configuration
configuration of the "Slice", such as its spatial position, size, and of the Slice, such as its spatial position, size, and aspect ratio.
aspect ratio. The pseudo-code below describes the contents of the The pseudocode below describes the contents of the Slice Header.
"Slice Header".
"Slice Header" has its own initial states, all set to 128. Slice Header has its own initial states, all set to 128.
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
SliceHeader( ) { | SliceHeader( ) { |
slice_x | ur slice_x | ur
slice_y | ur slice_y | ur
slice_width - 1 | ur slice_width - 1 | ur
slice_height - 1 | ur slice_height - 1 | ur
for (i = 0; i < quant_table_set_index_count; i++) { | for (i = 0; i < quant_table_set_index_count; i++) { |
quant_table_set_index[ i ] | ur quant_table_set_index[ i ] | ur
} | } |
picture_structure | ur picture_structure | ur
sar_num | ur sar_num | ur
sar_den | ur sar_den | ur
if (version >= 4) { | if (version >= 4) { |
reset_contexts | br reset_contexts | br
slice_coding_mode | ur slice_coding_mode | ur
} | } |
} | } |
4.6.1. slice_x 4.6.1. slice_x
"slice_x" indicates the x position on the slice raster formed by slice_x indicates the x position on the Slice raster formed by
num_h_slices. num_h_slices.
Inferred to be 0 if not present. Inferred to be 0 if not present.
4.6.2. slice_y 4.6.2. slice_y
"slice_y" indicates the y position on the slice raster formed by slice_y indicates the y position on the Slice raster formed by
num_v_slices. num_v_slices.
Inferred to be 0 if not present. Inferred to be 0 if not present.
4.6.3. slice_width 4.6.3. slice_width
"slice_width" indicates the width on the slice raster formed by slice_width indicates the width on the Slice raster formed by
num_h_slices. num_h_slices.
Inferred to be 1 if not present. Inferred to be 1 if not present.
4.6.4. slice_height 4.6.4. slice_height
"slice_height" indicates the height on the slice raster formed by slice_height indicates the height on the Slice raster formed by
num_v_slices. num_v_slices.
Inferred to be 1 if not present. Inferred to be 1 if not present.
4.6.5. quant_table_set_index_count 4.6.5. quant_table_set_index_count
"quant_table_set_index_count" is defined as: quant_table_set_index_count is defined as the following:
1 + ( ( chroma_planes || version <= 3 ) ? 1 : 0 ) 1 + ( ( chroma_planes || version <= 3 ) ? 1 : 0 )
+ ( extra_plane ? 1 : 0 ) + ( extra_plane ? 1 : 0 )
4.6.6. quant_table_set_index 4.6.6. quant_table_set_index
"quant_table_set_index" indicates the Quantization Table Set index to quant_table_set_index indicates the Quantization Table Set index to
select the Quantization Table Set and the initial states for the select the Quantization Table Set and the initial states for the
"Slice Content". Slice Content.
Inferred to be 0 if not present. Inferred to be 0 if not present.
4.6.7. picture_structure 4.6.7. picture_structure
"picture_structure" specifies the temporal and spatial relationship picture_structure specifies the temporal and spatial relationship of
of each Line of the Frame. each Line of the Frame.
Inferred to be 0 if not present. Inferred to be 0 if not present.
+=======+=========================+ +=======+=========================+
| value | picture structure used | | value | picture structure used |
+=======+=========================+ +=======+=========================+
| 0 | unknown | | 0 | unknown |
+-------+-------------------------+ +-------+-------------------------+
| 1 | top field first | | 1 | top field first |
+-------+-------------------------+ +-------+-------------------------+
| 2 | bottom field first | | 2 | bottom field first |
+-------+-------------------------+ +-------+-------------------------+
| 3 | progressive | | 3 | progressive |
+-------+-------------------------+ +-------+-------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------+ +-------+-------------------------+
Table 17 Table 16: The definitions for
picture_structure values.
4.6.8. sar_num 4.6.8. sar_num
"sar_num" specifies the Sample aspect ratio numerator. sar_num specifies the Sample aspect ratio numerator.
Inferred to be 0 if not present. Inferred to be 0 if not present.
A value of 0 means that aspect ratio is unknown. A value of 0 means that aspect ratio is unknown.
Encoders MUST write 0 if Sample aspect ratio is unknown. Encoders MUST write 0 if the Sample aspect ratio is unknown.
If "sar_den" is 0, decoders SHOULD ignore the encoded value and If sar_den is 0, decoders SHOULD ignore the encoded value and
consider that "sar_num" is 0. consider that sar_num is 0.
4.6.9. sar_den 4.6.9. sar_den
"sar_den" specifies the Sample aspect ratio denominator. sar_den specifies the Sample aspect ratio denominator.
Inferred to be 0 if not present. Inferred to be 0 if not present.
A value of 0 means that aspect ratio is unknown. A value of 0 means that aspect ratio is unknown.
Encoders MUST write 0 if Sample aspect ratio is unknown. Encoders MUST write 0 if the Sample aspect ratio is unknown.
If "sar_num" is 0, decoders SHOULD ignore the encoded value and If sar_num is 0, decoders SHOULD ignore the encoded value and
consider that "sar_den" is 0. consider that sar_den is 0.
4.6.10. reset_contexts 4.6.10. reset_contexts
"reset_contexts" indicates if slice contexts MUST be reset. reset_contexts indicates if Slice contexts MUST be reset.
Inferred to be 0 if not present. Inferred to be 0 if not present.
4.6.11. slice_coding_mode 4.6.11. slice_coding_mode
"slice_coding_mode" indicates the slice coding mode. slice_coding_mode indicates the Slice coding mode.
Inferred to be 0 if not present. Inferred to be 0 if not present.
+=======+=============================+ +=======+=============================+
| value | slice coding mode | | value | Slice coding mode |
+=======+=============================+ +=======+=============================+
| 0 | Range Coding or Golomb Rice | | 0 | Range Coding or Golomb Rice |
+-------+-----------------------------+ +-------+-----------------------------+
| 1 | raw PCM | | 1 | raw PCM |
+-------+-----------------------------+ +-------+-----------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-----------------------------+ +-------+-----------------------------+
Table 18 Table 17: The definitions for
slice_coding_mode values.
4.7. Slice Content 4.7. Slice Content
A "Slice Content" contains all Line elements part of the "Slice". A Slice Content contains all Line elements part of the Slice.
Depending on the configuration, Line elements are ordered by Plane Depending on the configuration, Line elements are ordered by Plane
then by row (YCbCr) or by row then by Plane (RGB). then by row (YCbCr) or by row then by Plane (RGB).
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
SliceContent( ) { | SliceContent( ) { |
if (colorspace_type == 0) { | if (colorspace_type == 0) { |
for (p = 0; p < primary_color_count; p++) { | for (p = 0; p < primary_color_count; p++) { |
for (y = 0; y < plane_pixel_height[ p ]; y++) { | for (y = 0; y < plane_pixel_height[ p ]; y++) { |
Line( p, y ) | Line( p, y ) |
} | } |
} | } |
} else if (colorspace_type == 1) { | } else if (colorspace_type == 1) { |
for (y = 0; y < slice_pixel_height; y++) { | for (y = 0; y < slice_pixel_height; y++) { |
for (p = 0; p < primary_color_count; p++) { | for (p = 0; p < primary_color_count; p++) { |
Line( p, y ) | Line( p, y ) |
} | } |
} | } |
} | } |
} | } |
4.7.1. primary_color_count 4.7.1. primary_color_count
"primary_color_count" is defined as: primary_color_count is defined as the following:
1 + ( chroma_planes ? 2 : 0 ) + ( extra_plane ? 1 : 0 ) 1 + ( chroma_planes ? 2 : 0 ) + ( extra_plane ? 1 : 0 )
4.7.2. plane_pixel_height 4.7.2. plane_pixel_height
"plane_pixel_height[ p ]" is the height in Pixels of Plane p of the plane_pixel_height[ p ] is the height in pixels of Plane p of the
"Slice". It is defined as: Slice. It is defined as the following:
chroma_planes == 1 && (p == 1 || p == 2) chroma_planes == 1 && (p == 1 || p == 2)
? ceil(slice_pixel_height / (1 << log2_v_chroma_subsample)) ? ceil(slice_pixel_height / (1 << log2_v_chroma_subsample))
: slice_pixel_height : slice_pixel_height
4.7.3. slice_pixel_height 4.7.3. slice_pixel_height
"slice_pixel_height" is the height in pixels of the slice. It is slice_pixel_height is the height in pixels of the Slice. It is
defined as: defined as the following:
floor( floor(
( slice_y + slice_height ) ( slice_y + slice_height )
* slice_pixel_height * slice_pixel_height
/ num_v_slices / num_v_slices
) - slice_pixel_y. ) - slice_pixel_y.
4.7.4. slice_pixel_y 4.7.4. slice_pixel_y
"slice_pixel_y" is the slice vertical position in pixels. It is slice_pixel_y is the Slice vertical position in pixels. It is
defined as: defined as the following:
floor( slice_y * frame_pixel_height / num_v_slices ) floor( slice_y * frame_pixel_height / num_v_slices )
4.8. Line 4.8. Line
A Line is a list of the sample differences (relative to the A Line is a list of the Sample Differences (relative to the
predictor) of primary color components. The pseudo-code below predictor) of primary color components. The pseudocode below
describes the contents of the Line. describes the contents of the Line.
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Line( p, y ) { | Line( p, y ) { |
if (colorspace_type == 0) { | if (colorspace_type == 0) { |
for (x = 0; x < plane_pixel_width[ p ]; x++) { | for (x = 0; x < plane_pixel_width[ p ]; x++) { |
sample_difference[ p ][ y ][ x ] | sd sample_difference[ p ][ y ][ x ] | sd
} | } |
} else if (colorspace_type == 1) { | } else if (colorspace_type == 1) { |
for (x = 0; x < slice_pixel_width; x++) { | for (x = 0; x < slice_pixel_width; x++) { |
sample_difference[ p ][ y ][ x ] | sd sample_difference[ p ][ y ][ x ] | sd
} | } |
} | } |
} | } |
4.8.1. plane_pixel_width 4.8.1. plane_pixel_width
"plane_pixel_width[ p ]" is the width in Pixels of Plane p of the plane_pixel_width[ p ] is the width in pixels of Plane p of the
"Slice". It is defined as: Slice. It is defined as the following:
chroma_planes == 1 && (p == 1 || p == 2) chroma_planes == 1 && (p == 1 || p == 2)
? ceil( slice_pixel_width / (1 << log2_h_chroma_subsample) ) ? ceil( slice_pixel_width / (1 << log2_h_chroma_subsample) )
: slice_pixel_width. : slice_pixel_width.
4.8.2. slice_pixel_width 4.8.2. slice_pixel_width
"slice_pixel_width" is the width in Pixels of the slice. It is slice_pixel_width is the width in pixels of the Slice. It is defined
defined as: as the following:
floor( floor(
( slice_x + slice_width ) ( slice_x + slice_width )
* slice_pixel_width * slice_pixel_width
/ num_h_slices / num_h_slices
) - slice_pixel_x ) - slice_pixel_x
4.8.3. slice_pixel_x 4.8.3. slice_pixel_x
"slice_pixel_x" is the slice horizontal position in Pixels. It is slice_pixel_x is the Slice horizontal position in pixels. It is
defined as: defined as the following:
floor( slice_x * frame_pixel_width / num_h_slices ) floor( slice_x * frame_pixel_width / num_h_slices )
4.8.4. sample_difference 4.8.4. sample_difference
"sample_difference[ p ][ y ][ x ]" is the sample difference for sample_difference[ p ][ y ][ x ] is the Sample Difference for Sample
Sample at Plane "p", y position "y", and x position "x". The Sample at Plane p, y position y, and x position x. The Sample value is
value is computed based on median predictor and context described in computed based on median predictor and context described in
Section 3.2. Section 3.2.
4.9. Slice Footer 4.9. Slice Footer
A "Slice Footer" provides information about slice size and A Slice Footer provides information about Slice size and (optionally)
(optionally) parity. The pseudo-code below describes the contents of parity. The pseudocode below describes the contents of the Slice
the "Slice Footer". Footer.
Note: "Slice Footer" is always byte aligned. Note: Slice Footer is always byte aligned.
pseudo-code | type pseudocode | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
SliceFooter( ) { | SliceFooter( ) { |
slice_size | u(24) slice_size | u(24)
if (ec) { | if (ec) { |
error_status | u(8) error_status | u(8)
slice_crc_parity | u(32) slice_crc_parity | u(32)
} | } |
} | } |
4.9.1. slice_size 4.9.1. slice_size
"slice_size" indicates the size of the slice in bytes. slice_size indicates the size of the Slice in bytes.
Note: this allows finding the start of slices before previous slices Note: this allows finding the start of Slices before previous Slices
have been fully decoded, and allows parallel decoding as well as have been fully decoded and allows parallel decoding as well as error
error resilience. resilience.
4.9.2. error_status 4.9.2. error_status
"error_status" specifies the error status. error_status specifies the error status.
+=======+======================================+ +=======+======================================+
| value | error status | | value | error status |
+=======+======================================+ +=======+======================================+
| 0 | no error | | 0 | no error |
+-------+--------------------------------------+ +-------+--------------------------------------+
| 1 | slice contains a correctable error | | 1 | Slice contains a correctable error |
+-------+--------------------------------------+ +-------+--------------------------------------+
| 2 | slice contains a uncorrectable error | | 2 | Slice contains a uncorrectable error |
+-------+--------------------------------------+ +-------+--------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+--------------------------------------+ +-------+--------------------------------------+
Table 19 Table 18: The definitions for error_status
values.
4.9.3. slice_crc_parity 4.9.3. slice_crc_parity
"slice_crc_parity" 32 bits that are chosen so that the slice as a slice_crc_parity is 32 bits that are chosen so that the Slice as a
whole has a crc remainder of 0. whole has a CRC remainder of 0.
This is equivalent to storing the crc remainder in the 32-bit parity. This is equivalent to storing the CRC remainder in the 32-bit parity.
The CRC generator polynomial used is the standard IEEE CRC polynomial The CRC generator polynomial used is the standard IEEE CRC polynomial
(0x104C11DB7), with initial value 0, without pre-inversion and (0x104C11DB7) with initial value 0, without pre-inversion, and
without post-inversion. without post-inversion.
5. Restrictions 5. Restrictions
To ensure that fast multithreaded decoding is possible, starting with To ensure that fast multithreaded decoding is possible, starting with
version 3 and if "frame_pixel_width * frame_pixel_height" is more version 3 and if frame_pixel_width * frame_pixel_height is more than
than 101376, "slice_width * slice_height" MUST be less or equal to 101376, slice_width * slice_height MUST be less or equal to
"num_h_slices * num_v_slices / 4". Note: 101376 is the frame size in num_h_slices * num_v_slices / 4. Note: 101376 is the frame size in
Pixels of a 352x288 frame also known as CIF ("Common Intermediate pixels of a 352x288 frame also known as CIF (Common Intermediate
Format") frame size format. Format) frame size format.
For each Frame, each position in the slice raster MUST be filled by For each Frame, each position in the Slice raster MUST be filled by
one and only one slice of the Frame (no missing slice position, no one and only one Slice of the Frame (no missing Slice position and no
slice overlapping). Slice overlapping).
For each Frame with "keyframe" value of 0, each slice MUST have the For each Frame with a keyframe value of 0, each Slice MUST have the
same value of "slice_x", "slice_y", "slice_width", "slice_height" as same value of slice_x, slice_y, slice_width, and slice_height as a
a slice in the previous Frame, except if "reset_contexts" is 1. Slice in the previous Frame, except if reset_contexts is 1.
6. Security Considerations 6. Security Considerations
Like any other codec, (such as [RFC6716]), FFV1 should not be used Like any other codec (such as [RFC6716]), FFV1 should not be used
with insecure ciphers or cipher-modes that are vulnerable to known with insecure ciphers or cipher modes that are vulnerable to known
plaintext attacks. Some of the header bits as well as the padding plaintext attacks. Some of the header bits as well as the padding
are easily predictable. are easily predictable.
Implementations of the FFV1 codec need to take appropriate security Implementations of the FFV1 codec need to take appropriate security
considerations into account. Those related to denial of service are considerations into account. Those related to denial of service are
outlined in Section 2.1 of [RFC4732]. It is extremely important for outlined in Section 2.1 of [RFC4732]. It is extremely important for
the decoder to be robust against malicious payloads. Malicious the decoder to be robust against malicious payloads. Malicious
payloads MUST NOT cause the decoder to overrun its allocated memory payloads MUST NOT cause the decoder to overrun its allocated memory
or to take an excessive amount of resources to decode. An overrun in or to take an excessive amount of resources to decode. An overrun in
allocated memory could lead to arbitrary code execution by an allocated memory could lead to arbitrary code execution by an
attacker. The same applies to the encoder, even though problems in attacker. The same applies to the encoder, even though problems in
encoders are typically rarer. Malicious video streams MUST NOT cause encoders are typically rarer. Malicious video streams MUST NOT cause
the encoder to misbehave because this would allow an attacker to the encoder to misbehave because this would allow an attacker to
attack transcoding gateways. A frequent security problem in image attack transcoding gateways. A frequent security problem in image
and video codecs is failure to check for integer overflows. An and video codecs is failure to check for integer overflows. An
example is allocating "frame_pixel_width * frame_pixel_height" in example is allocating frame_pixel_width * frame_pixel_height in pixel
Pixel count computations without considering that the multiplication count computations without considering that the multiplication result
result may have overflowed the arithmetic types range. The range may have overflowed the range of the arithmetic type. The range
coder could, if implemented naively, read one byte over the end. The coder could, if implemented naively, read one byte over the end. The
implementation MUST ensure that no read outside allocated and implementation MUST ensure that no read outside allocated and
initialized memory occurs. initialized memory occurs.
None of the content carried in FFV1 is intended to be executable. None of the content carried in FFV1 is intended to be executable.
7. IANA Considerations 7. IANA Considerations
The IANA is requested to register the following values: IANA has registered the following values.
7.1. Media Type Definition 7.1. Media Type Definition
This registration is done using the template defined in [RFC6838] and This registration is done using the template defined in [RFC6838] and
following [RFC4855]. following [RFC4855].
Type name: video Type name: video
Subtype name: FFV1 Subtype name: FFV1
Required parameters: None.
Optional parameters: These parameters are used to signal the Required parameters: None.
capabilities of a receiver implementation. These parameters MUST NOT
be used for any other purpose.
* "version": The "version" of the FFV1 encoding as defined by Optional parameters: These parameters are used to signal the
Section 4.2.1. capabilities of a receiver implementation. These parameters MUST
NOT be used for any other purpose.
* "micro_version": The "micro_version" of the FFV1 encoding as version: The version of the FFV1 encoding as defined by
defined by Section 4.2.2. Section 4.2.1.
* "coder_type": The "coder_type" of the FFV1 encoding as defined by micro_version: The micro_version of the FFV1 encoding as defined
Section 4.2.3. by Section 4.2.2.
* "colorspace_type": The "colorspace_type" of the FFV1 encoding as coder_type: The coder_type of the FFV1 encoding as defined by
defined by Section 4.2.5. Section 4.2.3.
* "bits_per_raw_sample": The "bits_per_raw_sample" of the FFV1 colorspace_type: The colorspace_type of the FFV1 encoding as
encoding as defined by Section 4.2.7. defined by Section 4.2.5.
* "max_slices": The value of "max_slices" is an integer indicating bits_per_raw_sample: The bits_per_raw_sample of the FFV1 encoding
the maximum count of slices with a frames of the FFV1 encoding. as defined by Section 4.2.7.
Encoding considerations: This media type is defined for encapsulation max_slices: The value of max_slices is an integer indicating the
in several audiovisual container formats and contains binary data; maximum count of Slices within a Frame of the FFV1 encoding.
see Section 4.3.3. This media type is framed binary data; see
Section 4.8 of [RFC6838].
Security considerations: See Section 6 of this document. Encoding considerations: This media type is defined for
encapsulation in several audiovisual container formats and
contains binary data; see Section 4.3.3. This media type is
framed binary data; see Section 4.8 of [RFC6838].
Interoperability considerations: None. Security considerations: See Section 6 of this document.
Published specification: RFC XXXX. Interoperability considerations: None.
Published specification: RFC XXXX.
[RFC Editor: Upon publication as an RFC, please replace "XXXX" with [RFC Editor: Upon publication as an RFC, please replace "XXXX" with
the number assigned to this document and remove this note.] the number assigned to this document and remove this note.]
Applications which use this media type: Any application that requires Applications that use this media type: Any application that requires
the transport of lossless video can use this media type. Some the transport of lossless video can use this media type. Some
examples are, but not limited to screen recording, scientific examples are, but not limited to, screen recording, scientific
imaging, and digital video preservation. imaging, and digital video preservation.
Fragment identifier considerations: N/A. Fragment identifier considerations: N/A.
Additional information: None. Additional information: None.
Person & email address to contact for further information: Michael Person & email address to contact for further information: Michael N
Niedermayer michael@niedermayer.cc (mailto:michael@niedermayer.cc) iedermayer (michael@niedermayer.cc
(mailto:michael@niedermayer.cc))
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: None. Restrictions on usage: None.
Author: Dave Rice dave@dericed.com (mailto:dave@dericed.com) Author: Dave Rice (dave@dericed.com (mailto:dave@dericed.com))
Change controller: IETF cellar working group delegated from the IESG. Change controller: IETF CELLAR Working Group delegated from the
IESG.
8. Changelog 8. Changelog
See https://github.com/FFmpeg/FFV1/commits/master See https://github.com/FFmpeg/FFV1/commits/master
(https://github.com/FFmpeg/FFV1/commits/master) (https://github.com/FFmpeg/FFV1/commits/master)
[RFC Editor: Please remove this Changelog section prior to [RFC Editor: Please remove this Changelog section prior to
publication.] publication.]
9. Normative References 9. Normative References
[ISO.15444-1.2016]
International Organization for Standardization,
"Information technology -- JPEG 2000 image coding system:
Core coding system", October 2016.
[ISO.9899.2018] [ISO.9899.2018]
International Organization for Standardization, International Organization for Standardization,
"Programming languages - C", ISO Standard 9899, 2018. "Information technology - Programming languages - C", ISO/
IEC 9899:2018, June 2018.
[Matroska] IETF, "Matroska", 2019, <https://datatracker.ietf.org/doc/
draft-ietf-cellar-matroska/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732, Denial-of-Service Considerations", RFC 4732,
DOI 10.17487/RFC4732, December 2006, DOI 10.17487/RFC4732, December 2006,
<https://www.rfc-editor.org/info/rfc4732>. <https://www.rfc-editor.org/info/rfc4732>.
[RFC4855] Casner, S., "Media Type Registration of RTP Payload [RFC4855] Casner, S., "Media Type Registration of RTP Payload
Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007, Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
<https://www.rfc-editor.org/info/rfc4855>. <https://www.rfc-editor.org/info/rfc4855>.
[RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the
Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716,
September 2012, <https://www.rfc-editor.org/info/rfc6716>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013, RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>. <https://www.rfc-editor.org/info/rfc6838>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
10. Informative References 10. Informative References
[Address-Sanitizer] [AddressSanitizer]
The Clang Team, "ASAN AddressSanitizer website", undated, Clang Project, "AddressSanitizer", Clang 12 documentation,
<https://clang.llvm.org/docs/AddressSanitizer.html>. <https://clang.llvm.org/docs/AddressSanitizer.html>.
[AVI] Microsoft, "AVI RIFF File Reference", undated, [AVI] Microsoft, "AVI RIFF File Reference",
<https://msdn.microsoft.com/en-us/library/windows/desktop/ <https://docs.microsoft.com/en-
dd318189%28v=vs.85%29.aspx>. us/windows/win32/directshow/avi-riff-file-reference>.
[FFV1GO] Buitenhuis, D., "FFV1 Decoder in Go", 2019, [FFV1GO] Buitenhuis, D., "FFV1 Decoder in Go", 2019,
<https://github.com/dwbuiten/go-ffv1>. <https://github.com/dwbuiten/go-ffv1>.
[HuffYUV] Rudiak-Gould, B., "HuffYUV", December 2003, [HuffYUV] Rudiak-Gould, B., "HuffYUV revisited", December 2003,
<https://web.archive.org/web/20040402121343/ <https://web.archive.org/web/20040402121343/
http://cultact-server.novi.dk/kpo/huffyuv/huffyuv.html>. http://cultact-server.novi.dk/kpo/huffyuv/huffyuv.html>.
[I-D.ietf-cellar-ffv1] [I-D.ietf-cellar-ffv1]
Niedermayer, M., Rice, D., and J. Martinez, "FFV1 Video Niedermayer, M., Rice, D., and J. Martinez, "FFV1 Video
Coding Format Version 0, 1, and 3", Work in Progress, Coding Format Version 0, 1, and 3", Work in Progress,
Internet-Draft, draft-ietf-cellar-ffv1-20, 23 February Internet-Draft, draft-ietf-cellar-ffv1-20, 23 February
2021, 2021, <https://datatracker.ietf.org/doc/html/draft-ietf-
<https://tools.ietf.org/html/draft-ietf-cellar-ffv1-20>. cellar-ffv1-20>.
[I-D.ietf-cellar-matroska]
Lhomme, S., Bunkus, M., and D. Rice, "Matroska Media
Container Format Specifications", Work in Progress,
Internet-Draft, draft-ietf-cellar-matroska-08, 9 October
2021, <https://datatracker.ietf.org/doc/html/draft-ietf-
cellar-matroska-08>.
[ISO.14495-1.1999] [ISO.14495-1.1999]
International Organization for Standardization, International Organization for Standardization,
"Information technology -- Lossless and near-lossless "Information technology -- Lossless and near-lossless
compression of continuous-tone still images: Baseline", compression of continuous-tone still images: Baseline",
December 1999. ISO/IEC 14495-1:1999, December 1999.
[ISO.14496-10.2014] [ISO.14496-10.2020]
International Organization for Standardization, International Organization for Standardization,
"Information technology -- Coding of audio-visual objects "Information technology -- Coding of audio-visual objects
-- Part 10: Advanced Video Coding", September 2014. -- Part 10: Advanced Video Coding", ISO/IEC 14496-10:2020,
December 2020.
[ISO.14496-12.2015] [ISO.14496-12.2020]
International Organization for Standardization, International Organization for Standardization,
"Information technology -- Coding of audio-visual objects "Information technology -- Coding of audio-visual objects
-- Part 12: ISO base media file format", December 2015. -- Part 12: ISO base media file format", ISO/IEC
14496-12:2020, December 2020.
[ISO.15444-1.2019]
International Organization for Standardization,
"Information technology -- JPEG 2000 image coding system:
Core coding system", ISO/IEC 15444-1:2019, October 2019.
[MediaConch] [MediaConch]
MediaArea.net, "MediaConch", 2018, MediaArea.net, "MediaConch", 2018,
<https://mediaarea.net/MediaConch>. <https://mediaarea.net/MediaConch>.
[NUT] Niedermayer, M., "NUT Open Container Format", December [NUT] Niedermayer, M., "NUT Open Container Format", December
2013, <https://ffmpeg.org/~michael/nut.txt>. 2013, <https://ffmpeg.org/~michael/nut.txt>.
[range-coding] [Range-Encoding]
Martin, G. N. N., "Range encoding: an algorithm for Martin, G. N. N., "Range encoding: an algorithm for
removing redundancy from a digitised message", Proceedings removing redundancy from a digitised message", Institution
of the Conference on Video and Data Recording. Institution
of Electronic and Radio Engineers, Hampshire, England, of Electronic and Radio Engineers, Hampshire, England,
July 1979. July 1979.
[REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the [REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the
FFV1 codec in FFmpeg", undated, <https://ffmpeg.org>. FFV1 codec in FFmpeg",
<https://ffmpeg.org/doxygen/trunk/ffv1_8h.html>.
[VALGRIND] Valgrind Developers, "Valgrind website", undated, [RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the
Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716,
September 2012, <https://www.rfc-editor.org/info/rfc6716>.
[Valgrind] Valgrind Developers, "Valgrind website",
<https://valgrind.org/>. <https://valgrind.org/>.
[YCbCr] Wikipedia, "YCbCr", undated, [YCbCr] Wikipedia, "YCbCr", 25 May 2021,
<https://en.wikipedia.org/w/index.php?title=YCbCr>. <https://en.wikipedia.org/w/
index.php?title=YCbCr&oldid=1025097882>.
Appendix A. Multi-theaded decoder implementation suggestions Appendix A. Multithreaded Decoder Implementation Suggestions
This appendix is informative. This appendix is informative.
The FFV1 bitstream is parsable in two ways: in sequential order as The FFV1 bitstream is parsable in two ways: in sequential order as
described in this document or with the pre-analysis of the footer of described in this document or with the pre-analysis of the footer of
each slice. Each slice footer contains a "slice_size" field so the each Slice. Each Slice footer contains a slice_size field so the
boundary of each slice is computable without having to parse the boundary of each Slice is computable without having to parse the
slice content. That allows multi-threading as well as independence Slice content. That allows multithreading as well as independence of
of slice content (a bitstream error in a slice header or slice Slice content (a bitstream error in a Slice header or Slice content
content has no impact on the decoding of the other slices). has no impact on the decoding of the other Slices).
After having checked "keyframe" field, a decoder SHOULD parse After having checked the keyframe field, a decoder SHOULD parse
"slice_size" fields, from "slice_size" of the last slice at the end slice_size fields, from slice_size of the last Slice at the end of
of the "Frame" up to "slice_size" of the first slice at the beginning the Frame up to slice_size of the first Slice at the beginning of the
of the "Frame", before parsing slices, in order to have slices Frame before parsing Slices, in order to have Slice boundaries. A
boundaries. A decoder MAY fallback on sequential order e.g. in case decoder MAY fall back on sequential order e.g., in case of a
of a corrupted "Frame" (frame size unknown, "slice_size" of slices corrupted Frame (e.g., frame size unknown or slice_size of Slices not
not coherent...) or if there is no possibility of seeking into the coherent) or if there is no possibility of seeking into the stream.
stream.
Appendix B. Future handling of some streams created by non conforming Appendix B. Future Handling of Some Streams Created by Nonconforming
encoders Encoders
This appendix is informative. This appendix is informative.
Some bitstreams were found with 40 extra bits corresponding to Some bitstreams were found with 40 extra bits corresponding to
"error_status" and "slice_crc_parity" in the "reserved" bits of error_status and slice_crc_parity in the reserved bits of Slice. Any
"Slice()". Any revision of this specification SHOULD care about revision of this specification should avoid adding 40 bits of content
avoiding to add 40 bits of content after "SliceContent" if "version" after SliceContent if version == 0 or version == 1, otherwise a
== 0 or "version" == 1. Else a decoder conforming to the revised decoder conforming to the revised specification could not distinguish
specification could not distinguish between a revised bitstream and between a revised bitstream and such buggy bitstream in the wild.
such buggy bitstream in the wild.
Appendix C. FFV1 Implementations Appendix C. FFV1 Implementations
This appendix provides references to a few notable implementations of This appendix provides references to a few notable implementations of
FFV1. FFV1.
C.1. FFmpeg FFV1 Codec C.1. FFmpeg FFV1 Codec
This reference implementation [REFIMPL] contains no known buffer This reference implementation [REFIMPL] contains no known buffer
overflow or cases where a specially crafted packet or video segment overflow or cases where a specially crafted packet or video segment
skipping to change at page 57, line 42 skipping to change at page 56, line 41
* Sending the decoder valid packets generated by the reference * Sending the decoder valid packets generated by the reference
encoder and verifying that the decoder's output matches the encoder and verifying that the decoder's output matches the
encoder's input. encoder's input.
* Sending the decoder packets generated by the reference encoder and * Sending the decoder packets generated by the reference encoder and
then subjected to random corruption. then subjected to random corruption.
* Sending the decoder random packets that are not FFV1. * Sending the decoder random packets that are not FFV1.
In all of the conditions above, the decoder and encoder was run In all of the conditions above, the decoder and encoder was run
inside the [VALGRIND] memory debugger as well as clangs address inside the Valgrind memory debugger [Valgrind] as well as the Clang
sanitizer [Address-Sanitizer], which track reads and writes to AddressSanitizer [AddressSanitizer], which tracks reads and writes to
invalid memory regions as well as the use of uninitialized memory. invalid memory regions as well as the use of uninitialized memory.
There were no errors reported on any of the tested conditions. There were no errors reported on any of the tested conditions.
C.2. FFV1 Decoder in Go C.2. FFV1 Decoder in Go
An FFV1 decoder was [FFV1GO] written in Go by Derek Buitenhuis during An FFV1 decoder [FFV1GO] was written in Go by Derek Buitenhuis during
the work to development this document. the work to develop this document.
C.3. MediaConch C.3. MediaConch
The developers of the MediaConch project [MediaConch] created an The developers of the MediaConch project [MediaConch] created an
independent FFV1 decoder as part of that project to validate FFV1 independent FFV1 decoder as part of that project to validate FFV1
bitstreams. This work led to the discovery of three conflicts bitstreams. This work led to the discovery of three conflicts
between existing FFV1 implementations and this document without the between existing FFV1 implementations and draft versions of this
added exceptions. document. These issues are addressed by Section 3.3.1,
Section 3.7.2.1, and Appendix B.
Authors' Addresses Authors' Addresses
Michael Niedermayer Michael Niedermayer
Email: michael@niedermayer.cc Email: michael@niedermayer.cc
Dave Rice Dave Rice
Email: dave@dericed.com Email: dave@dericed.com
Jerome Martinez Jérôme Martinez
Email: jerome@mediaarea.net Email: jerome@mediaarea.net
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