--- 1/draft-ietf-cellar-ffv1-v4-08.txt 2020-01-27 15:14:18.481085555 -0800 +++ 2/draft-ietf-cellar-ffv1-v4-09.txt 2020-01-27 15:14:18.593088415 -0800 @@ -1,18 +1,20 @@ cellar M. Niedermayer -Internet-Draft D. Rice -Intended status: Standards Track J. Martinez -Expires: 25 April 2020 23 October 2019 +Internet-Draft +Intended status: Standards Track D. Rice +Expires: 30 July 2020 + J. Martinez + 27 January 2020 FFV1 Video Coding Format Version 4 - draft-ietf-cellar-ffv1-v4-08 + draft-ietf-cellar-ffv1-v4-09 Abstract This document defines FFV1, a lossless intra-frame video encoding format. FFV1 is designed to efficiently compress video data in a variety of pixel formats. Compared to uncompressed video, FFV1 offers storage compression, frame fixity, and self-description, which makes FFV1 useful as a preservation or intermediate video format. Status of This Memo @@ -23,25 +25,25 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on 25 April 2020. + This Internet-Draft will expire on 30 July 2020. Copyright Notice - Copyright (c) 2019 IETF Trust and the persons identified as the + Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. @@ -54,133 +56,129 @@ 2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 5 2.2.1. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 5 2.2.2. Arithmetic Operators . . . . . . . . . . . . . . . . 5 2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 6 2.2.4. Comparison Operators . . . . . . . . . . . . . . . . 6 2.2.5. Mathematical Functions . . . . . . . . . . . . . . . 7 2.2.6. Order of Operation Precedence . . . . . . . . . . . . 7 2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 8 2.2.9. Bitstream Functions . . . . . . . . . . . . . . . . . 8 - 3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 9 + 3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 10 + 3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3. Median Predictor . . . . . . . . . . . . . . . . . . . . 10 3.4. Context . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.5. Quantization Table Sets . . . . . . . . . . . . . . . . . 11 - 3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 12 + 3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 11 3.7. Color spaces . . . . . . . . . . . . . . . . . . . . . . 12 3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 12 3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 3.8. Coding of the Sample Difference . . . . . . . . . . . . . 15 - 3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 15 - 3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 20 - 4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 25 - 4.1. Parameters . . . . . . . . . . . . . . . . . . . . . . . 26 - 4.1.1. version . . . . . . . . . . . . . . . . . . . . . . . 28 - 4.1.2. micro_version . . . . . . . . . . . . . . . . . . . . 28 - 4.1.3. coder_type . . . . . . . . . . . . . . . . . . . . . 29 - 4.1.4. state_transition_delta . . . . . . . . . . . . . . . 30 - 4.1.5. colorspace_type . . . . . . . . . . . . . . . . . . . 30 - 4.1.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 31 - 4.1.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 31 - 4.1.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 31 - 4.1.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 32 - 4.1.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 32 - 4.1.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 32 - 4.1.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 32 - 4.1.13. quant_table_set_count . . . . . . . . . . . . . . . . 32 - 4.1.14. states_coded . . . . . . . . . . . . . . . . . . . . 32 - 4.1.15. initial_state_delta . . . . . . . . . . . . . . . . . 33 - 4.1.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 33 - 4.1.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 33 - 4.2. Configuration Record . . . . . . . . . . . . . . . . . . 34 - 4.2.1. reserved_for_future_use . . . . . . . . . . . . . . . 34 - 4.2.2. configuration_record_crc_parity . . . . . . . . . . . 34 - 4.2.3. Mapping FFV1 into Containers . . . . . . . . . . . . 35 - 4.3. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 36 - 4.4. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 37 - 4.5. Slice Header . . . . . . . . . . . . . . . . . . . . . . 38 - 4.5.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 39 - 4.5.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 39 - 4.5.3. slice_width . . . . . . . . . . . . . . . . . . . . . 39 - 4.5.4. slice_height . . . . . . . . . . . . . . . . . . . . 39 - 4.5.5. quant_table_set_index_count . . . . . . . . . . . . . 40 - 4.5.6. quant_table_set_index . . . . . . . . . . . . . . . . 40 - 4.5.7. picture_structure . . . . . . . . . . . . . . . . . . 40 - 4.5.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 40 - 4.5.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 41 - 4.5.10. reset_contexts . . . . . . . . . . . . . . . . . . . 41 - 4.5.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 41 - 4.6. Slice Content . . . . . . . . . . . . . . . . . . . . . . 41 - 4.6.1. primary_color_count . . . . . . . . . . . . . . . . . 42 - 4.6.2. plane_pixel_height . . . . . . . . . . . . . . . . . 42 - 4.6.3. slice_pixel_height . . . . . . . . . . . . . . . . . 42 - 4.6.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 42 - 4.7. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 43 - 4.7.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 43 - 4.7.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 43 - 4.7.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 43 - 4.7.4. sample_difference . . . . . . . . . . . . . . . . . . 44 - 4.8. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 44 - 4.8.1. slice_size . . . . . . . . . . . . . . . . . . . . . 44 - 4.8.2. error_status . . . . . . . . . . . . . . . . . . . . 44 - 4.8.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 45 - 4.9. Quantization Table Set . . . . . . . . . . . . . . . . . 45 - 4.9.1. quant_tables . . . . . . . . . . . . . . . . . . . . 46 - 4.9.2. context_count . . . . . . . . . . . . . . . . . . . . 46 - 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 47 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 47 - 7. Media Type Definition . . . . . . . . . . . . . . . . . . . . 48 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50 - 9. Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . 50 - 9.1. Decoder implementation suggestions . . . . . . . . . . . 50 - 9.1.1. Multi-threading Support and Independence of - Slices . . . . . . . . . . . . . . . . . . . . . . . 50 - 10. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 50 - 11. Normative References . . . . . . . . . . . . . . . . . . . . 50 - 12. Informative References . . . . . . . . . . . . . . . . . . . 51 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 52 + 3.8. Coding of the Sample Difference . . . . . . . . . . . . . 14 + 3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 14 + 3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 19 + 4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 24 + 4.1. Parameters . . . . . . . . . . . . . . . . . . . . . . . 25 + 4.1.1. version . . . . . . . . . . . . . . . . . . . . . . . 27 + 4.1.2. micro_version . . . . . . . . . . . . . . . . . . . . 27 + 4.1.3. coder_type . . . . . . . . . . . . . . . . . . . . . 28 + 4.1.4. state_transition_delta . . . . . . . . . . . . . . . 29 + 4.1.5. colorspace_type . . . . . . . . . . . . . . . . . . . 29 + 4.1.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 30 + 4.1.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 30 + 4.1.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 30 + 4.1.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 31 + 4.1.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 31 + 4.1.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 31 + 4.1.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 31 + 4.1.13. quant_table_set_count . . . . . . . . . . . . . . . . 31 + 4.1.14. states_coded . . . . . . . . . . . . . . . . . . . . 31 + 4.1.15. initial_state_delta . . . . . . . . . . . . . . . . . 32 + 4.1.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 32 + 4.1.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 32 + 4.2. Configuration Record . . . . . . . . . . . . . . . . . . 33 + 4.2.1. reserved_for_future_use . . . . . . . . . . . . . . . 33 + 4.2.2. configuration_record_crc_parity . . . . . . . . . . . 33 + 4.2.3. Mapping FFV1 into Containers . . . . . . . . . . . . 34 + 4.3. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 35 + 4.4. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 36 + 4.5. Slice Header . . . . . . . . . . . . . . . . . . . . . . 37 + 4.5.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 38 + 4.5.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 38 + 4.5.3. slice_width . . . . . . . . . . . . . . . . . . . . . 38 + 4.5.4. slice_height . . . . . . . . . . . . . . . . . . . . 38 + 4.5.5. quant_table_set_index_count . . . . . . . . . . . . . 39 + 4.5.6. quant_table_set_index . . . . . . . . . . . . . . . . 39 + 4.5.7. picture_structure . . . . . . . . . . . . . . . . . . 39 + 4.5.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 39 + 4.5.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 40 + 4.5.10. reset_contexts . . . . . . . . . . . . . . . . . . . 40 + 4.5.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 40 + 4.6. Slice Content . . . . . . . . . . . . . . . . . . . . . . 40 + 4.6.1. primary_color_count . . . . . . . . . . . . . . . . . 41 + 4.6.2. plane_pixel_height . . . . . . . . . . . . . . . . . 41 + 4.6.3. slice_pixel_height . . . . . . . . . . . . . . . . . 41 + 4.6.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 41 + 4.7. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 42 + 4.7.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 42 + 4.7.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 42 + 4.7.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 42 + 4.7.4. sample_difference . . . . . . . . . . . . . . . . . . 43 + 4.8. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 43 + 4.8.1. slice_size . . . . . . . . . . . . . . . . . . . . . 43 + 4.8.2. error_status . . . . . . . . . . . . . . . . . . . . 43 + 4.8.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 44 + 4.9. Quantization Table Set . . . . . . . . . . . . . . . . . 44 + 4.9.1. quant_tables . . . . . . . . . . . . . . . . . . . . 45 + 4.9.2. context_count . . . . . . . . . . . . . . . . . . . . 45 + 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 46 + 6. Security Considerations . . . . . . . . . . . . . . . . . . . 46 + 7. Media Type Definition . . . . . . . . . . . . . . . . . . . . 47 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 48 + 9. Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . 49 + 9.1. Decoder implementation suggestions . . . . . . . . . . . 49 + 9.1.1. Multi-threading Support and Independence of Slices . 49 + 10. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 49 + 11. Normative References . . . . . . . . . . . . . . . . . . . . 49 + 12. Informative References . . . . . . . . . . . . . . . . . . . 50 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51 1. Introduction This document describes FFV1, a lossless video encoding format. The design of FFV1 considers the storage of image characteristics, data fixity, and the optimized use of encoding time and storage requirements. FFV1 is designed to support a wide range of lossless video applications such as long-term audiovisual preservation, scientific imaging, screen recording, and other video encoding scenarios that seek to avoid the generational loss of lossy video encodings. This document defines a version 4 of FFV1. Prior versions of FFV1 are defined within [I-D.ietf-cellar-ffv1]. - The latest version of this document is available at - https://raw.github.com/FFmpeg/FFV1/master/ffv1.md - (https://raw.github.com/FFmpeg/FFV1/master/ffv1.md) - This document assumes familiarity with mathematical and coding concepts such as Range coding [range-coding] and YCbCr color spaces [YCbCr]. 2. Notation and Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this - document are to be interpreted as described in [RFC2119]. + "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and + "OPTIONAL" in this document are to be interpreted as described in BCP + 14 [RFC2119] [RFC8174] when, and only when, they appear in all + capitals, as shown here. 2.1. Definitions - "Container": Format that encapsulates "Frames" (see the section on - Frames (#frame)) and (when required) a "Configuration Record" into a - bitstream. + "Container": Format that encapsulates "Frames" (see Section 4.3) and + (when required) a "Configuration Record" into a bitstream. "Sample": The smallest addressable representation of a color component or a luma component in a "Frame". Examples of "Sample" are Luma, Blue Chrominance, Red Chrominance, Transparency, Red, Green, and Blue. "Plane": A discrete component of a static image comprised of "Samples" that represent a specific quantification of "Samples" of that image. @@ -217,26 +215,26 @@ 2.2. Conventions 2.2.1. Pseudo-code The FFV1 bitstream is described in this document using pseudo-code. Note that the pseudo-code is used for clarity in order to illustrate the structure of FFV1 and not intended to specify any particular implementation. The pseudo-code used is based upon the C programming language [ISO.9899.1990] and uses its "if/else", "while" and "for" - functions as well as functions defined within this document. + keywords as well as functions defined within this document. 2.2.2. Arithmetic Operators Note: the operators and the order of precedence are the same as used - in the C programming language [ISO.9899.1990]. + in the C programming language [ISO.9899.2018]. "a + b" means a plus b. "a - b" means a minus b. "-a" means negation of a. "a * b" means a multiplied by b. "a / b" means a divided by b. @@ -337,23 +335,22 @@ a = b, a += b, a -= b, a *= b 2.2.7. Range "a...b" means any value starting from a to b, inclusive. 2.2.8. NumBytes "NumBytes" is a non-negative integer that expresses the size in 8-bit octets of a particular FFV1 "Configuration Record" or "Frame". FFV1 - relies on its "Container" to store the "NumBytes" values, see the - section on the Mapping FFV1 into Containers (#mapping-ffv1-into- - containers). + relies on its "Container" to store the "NumBytes" values; see + Section 4.2.3. 2.2.9. Bitstream Functions 2.2.9.1. remaining_bits_in_bitstream "remaining_bits_in_bitstream( )" means the count of remaining bits after the pointer in that "Configuration Record" or "Frame". It is computed from the "NumBytes" value multiplied by 8 minus the count of bits of that "Configuration Record" or "Frame" already read by the bitstream parser. @@ -369,82 +366,85 @@ )" is a multiple of 8, otherwise false. 2.2.9.4. get_bits "get_bits( i )" is the action to read the next "i" bits in the bitstream, from most significant bit to least significant bit, and to return the corresponding value. The pointer is increased by "i". 3. Sample Coding - For each "Slice" (as described in the section on Slices (#slice)) of - a "Frame", the "Planes", "Lines", and "Samples" are coded in an order - determined by the "Color Space" (see the section on Color Space - (#color-spaces)). Each "Sample" is predicted by the median predictor - as described in the section of the Median Predictor (#median- - predictor) from other "Samples" within the same "Plane" and the - difference is stored using the method described in Coding of the - Sample Difference (#coding-of-the-sample-difference). + For each "Slice" (as described in Section 4.4) of a "Frame", the + "Planes", "Lines", and "Samples" are coded in an order determined by + the "Color Space" (see Section 3.7). Each "Sample" is predicted by + the median predictor as described in Section 3.3 from other "Samples" + within the same "Plane" and the difference is stored using the method + described in Section 3.8. 3.1. Border A border is assumed for each coded "Slice" for the purpose of the median predictor and context according to the following rules: * 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 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 "0" * 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 slice * 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" - The following table depicts a slice of 9 "Samples" - "a,b,c,d,e,f,g,h,i" in a 3x3 arrangement along with its assumed - border. + Figure 1 depicts a slice of 9 "Samples" "a,b,c,d,e,f,g,h,i" in a 3x3 + arrangement along with its assumed border. +---+---+---+---+---+---+---+---+ | 0 | 0 | | 0 | 0 | 0 | | 0 | +---+---+---+---+---+---+---+---+ | 0 | 0 | | 0 | 0 | 0 | | 0 | +---+---+---+---+---+---+---+---+ | | | | | | | | | +---+---+---+---+---+---+---+---+ | 0 | 0 | | a | b | c | | c | +---+---+---+---+---+---+---+---+ | 0 | a | | d | e | f | | f | +---+---+---+---+---+---+---+---+ | 0 | d | | g | h | i | | i | +---+---+---+---+---+---+---+---+ + Figure 1: A depiction of FFV1's assumed border for a set example + Samples. + 3.2. Samples Relative to any "Sample" "X", six other relatively positioned "Samples" from the coded "Samples" and presumed border are identified - according to the labels used in the following diagram. The labels - for these relatively positioned "Samples" are used within the median - predictor and context. + according to the labels used in Figure 2. The labels for these + relatively positioned "Samples" are used within the median predictor + and context. +---+---+---+---+ | | | T | | +---+---+---+---+ | |tl | t |tr | +---+---+---+---+ | L | l | X | | +---+---+---+---+ + Figure 2: A depiction of how relatively positions Samples are + references within this document. + The labels for these relative "Samples" are made of the first letters of the words Top, Left and Right. 3.3. Median Predictor The prediction for any "Sample" value at position "X" may be computed based upon the relative neighboring values of "l", "t", and "tl" via this equation: "median(l, t, l + t - tl)". @@ -483,41 +483,41 @@ Relative to any "Sample" "X", the Quantized Sample Differences "L-l", "l-tl", "tl-t", "T-t", and "t-tr" are used as context: context = Q_{0}[l - tl] + Q_{1}[tl - t] + Q_{2}[t - tr] + Q_{3}[L - l] + Q_{4}[T - t] - Figure 1 + Figure 3 If "context >= 0" then "context" is used and the difference between the "Sample" and its predicted value is encoded as is, else "-context" is used and the difference between the "Sample" and its predicted value is encoded with a flipped sign. 3.5. Quantization Table Sets The FFV1 bitstream contains 1 or more Quantization Table Sets. Each Quantization Table Set contains exactly 5 Quantization Tables with each Quantization Table corresponding to 1 of the 5 Quantized Sample Differences. For each Quantization Table, both the number of quantization steps and their distribution are stored in the FFV1 bitstream; each Quantization Table has exactly 256 entries, and the 8 least significant bits of the Quantized Sample Difference are used as index: Q_{j}[k] = quant_tables[i][j][k&255] - Figure 2 + Figure 4 In this formula, "i" is the Quantization Table Set index, "j" is the Quantized Table index, "k" the Quantized Sample Difference. 3.6. Quantization Table Set Indexes For each "Plane" of each slice, a Quantization Table Set is selected from an index: * For Y "Plane", "quant_table_set_index[ 0 ]" index is used @@ -583,53 +582,53 @@ [ISO.15444-1.2016]. Reversible Pixel transformations between YCbCr and RGB use the following formulae. Cb=b-g Cr=r-g Y=g+(Cb+Cr)>>2 g=Y-(Cb+Cr)>>2 r=Cr+g b=Cb+g - Figure 3 + Figure 5 Exception for the JPEG2000-RCT conversion: if bits_per_raw_sample is between 9 and 15 inclusive and extra_plane is 0, the following formulae for reversible conversions between YCbCr and RGB MUST be used instead of the ones above: Cb=g-b Cr=r-b Y=b+(Cb+Cr)>>2 b=Y-(Cb+Cr)>>2 r=Cr+b g=Cb+b - Figure 4 + Figure 6 Background: At the time of this writing, in all known implementations of 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" during both encoding and decoding. In the meanwhile, 16-bit JPEG2000-RCT was implemented without this issue in one implementation and validated by one conformance checker. Methods to address this exception for the transform are under consideration for the next version of the FFV1 bitstream. When FFV1 uses the JPEG2000-RCT, the horizontal "Lines" are interleaved to improve caching efficiency since it is most likely that the JPEG2000-RCT will immediately be converted to RGB during decoding. The interleaved coding order is also Y, then Cb, then Cr, and then if used transparency. As an example, a "Frame" that is two "Pixels" wide and two "Pixels" - high, could be comprised of the following structure: + high, could comprise the following structure: +------------------------+------------------------+ | Pixel(1,1) | Pixel(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) | | 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 @@ -644,83 +643,82 @@ 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 n (or n+1, in the case of JPEG2000-RCT) least significant bits are used, since this is sufficient to recover the original "Sample". In the equation below, the term "bits" represents bits_per_raw_sample+1 for JPEG2000-RCT or bits_per_raw_sample otherwise: coder_input = [(sample_difference + 2^(bits-1)) & (2^bits - 1)] - 2^(bits-1) - Figure 5 + Figure 7 3.8.1. Range Coding Mode 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 patent/royalty situation, as well as its slightly worse performance, CABAC was replaced by a Range coder based on an algorithm defined by G. Nigel and N. Martin in 1979 [range-coding]. 3.8.1.1. Range Binary Values To encode binary digits efficiently a Range coder is used. "C~i~" is the i-th Context. "B~i~" is the i-th byte of the bytestream. "b~i~" is the i-th Range coded binary value, "S~0,i~" is the i-th initial state. The length of the bytestream encoding n binary symbols is "j~n~" bytes. r_{i} = floor( ( R_{i} * S_{i,C_{i}} ) / 2^8 ) - Figure 6 + Figure 8 - S_{i+1,C_{i}} = zero_state_{S_{i,C_{i}}} XOR - l_i = L_i XOR + S_{i+1,C_{i}} = zero_state_{S_{i,C_{i}}} AND + l_i = L_i AND t_i = R_i - r_i <== b_i = 0 <==> L_i < R_i - r_i - S_{i+1,C_{i}} = one_state_{S_{i,C_{i}}} XOR - l_i = L_i - R_i + r_i XOR + S_{i+1,C_{i}} = one_state_{S_{i,C_{i}}} AND + l_i = L_i - R_i + r_i AND t_i = r_i <== b_i = 1 <==> L_i >= R_i - r_i - Figure 7 + Figure 9 S_{i+1,k} = S_{i,k} <== C_i != k - Figure 8 + Figure 10 - R_{i+1} = 2^8 * t_{i} XOR - L_{i+1} = 2^8 * l_{i} + B_{j_{i}} XOR + R_{i+1} = 2^8 * t_{i} AND + L_{i+1} = 2^8 * l_{i} + B_{j_{i}} AND j_{i+1} = j_{i} + 1 <== t_{i} < 2^8 - R_{i+1} = t_{i} XOR - L_{i+1} = l_{i} XOR + R_{i+1} = t_{i} AND + L_{i+1} = l_{i} AND j_{i+1} = j_{i} <== t_{i} >= 2^8 - Figure 9 + Figure 11 R_{0} = 65280 - Figure 10 + Figure 12 L_{0} = 2^8 * B_{0} + B_{1} - - Figure 11 + Figure 13 j_{0} = 2 - Figure 12 + Figure 14 3.8.1.1.1. Termination The range coder can be used in 3 modes. * In "Open mode" when decoding, every symbol the reader attempts to read is available. In this mode arbitrary data can have been appended without affecting the range coder output. This mode is not used in FFV1. @@ -757,22 +755,22 @@ To encode scalar integers, it would be possible to encode each bit separately and use the past bits as context. However that would mean 255 contexts per 8-bit symbol that is not only a waste of memory but also requires more past data to reach a reasonably good estimate of the probabilities. Alternatively assuming a Laplacian distribution and only dealing with its variance and mean (as in Huffman coding) would also be possible, however, for maximum flexibility and simplicity, the chosen method uses a single symbol to encode if a number is 0, and if not, encodes the number using its exponent, - mantissa and sign. The exact contexts used are best described by the - following code, followed by some comments. + mantissa and sign. The exact contexts used are best described by + Figure 15, followed by some comments. pseudo-code | type --------------------------------------------------------------|----- void put_symbol(RangeCoder *c, uint8_t *state, int v, int \ | is_signed) { | int i; | put_rac(c, state+0, !v); | if (v) { | int a= abs(v); | int e= log2(a); | @@ -785,37 +783,41 @@ for (i = e-1; i >= 0; i--) { | put_rac(c, state+22+min(i,9), (a>>i)&1); //22..31 | } | | if (is_signed) { | put_rac(c, state+11 + min(e, 10), v < 0); //11..21| } | } | } | + Figure 15: A pseudo-code description of the contexts of Range Non + Binary Values. + 3.8.1.3. Initial Values for the Context Model At keyframes all Range coder state variables are set to their initial state. 3.8.1.4. State Transition Table one_state_{i} = default_state_transition_{i} + state_transition_delta_{i} - Figure 13 + Figure 16 zero_state_{i} = 256 - one_state_{256-i} - Figure 14 + Figure 17 3.8.1.5. default_state_transition + 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, 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, 74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, @@ -838,26 +840,25 @@ 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, 241,242,243,244,245,246,247,248,248, 0, 0, 0, 0, 0, 0, 0, 3.8.1.6. Alternative State Transition Table The alternative state transition table has been built using iterative minimization of frame sizes and generally performs better than the - default. To use it, the coder_type (see the section on coder_type - (#codertype)) MUST be set to 2 and the difference to the default MUST - be stored in the "Parameters", see the section on Parameters - (#parameters). The reference implementation of FFV1 in FFmpeg uses - this table by default at the time of this writing when Range coding - is used. + default. To use it, the coder_type (see Section 4.1.3) MUST be set + to 2 and the difference to the default MUST be stored in the + "Parameters", see Section 4.1. The reference implementation of FFV1 + in FFmpeg uses Figure 18 by default at the time of this writing when + Range coding is used. 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, 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, 87, 82, 71, 97, 73, 73, 82, 75,111, 77, 94, 78, 87, 81, 83, 97, @@ -877,20 +878,22 @@ 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, 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, 241,243,242,244,245,246,247,248,249,250,251,252,252,253,254,255, + Figure 18: Alternative state transition table for Range coding. + 3.8.2. Golomb Rice Mode The end of the bitstream of the "Frame" is filled with 0-bits until that the bitstream contains a multiple of 8 bits. 3.8.2.1. Signed Golomb Rice Codes This coding mode uses Golomb Rice codes. The VLC is split into 2 parts, the prefix stores the most significant bits and the suffix stores the k least significant bits or stores the whole number in the @@ -1078,48 +1081,45 @@ error_sum = 4; bias = 0; count = 1; 4. Bitstream An FFV1 bitstream is composed of a series of 1 or more "Frames" and (when required) a "Configuration Record". Within the following sub-sections, pseudo-code is used to explain the - structure of each FFV1 bitstream component, as described in the - section on Pseudo-Code (#pseudocode). The following table lists - symbols used to annotate that pseudo-code in order to define the - storage of the data referenced in that line of pseudo-code. + structure of each FFV1 bitstream component, as described in + Section 2.2.1. Table 4 lists symbols used to annotate that pseudo- + code in order to define the storage of the data referenced in that + line of pseudo-code. - +--------+-------------------------------------------+ + +--------+----------------------------------------------+ | Symbol | Definition | - +========+===========================================+ + +========+==============================================+ | u(n) | unsigned big endian integer using n bits | - +--------+-------------------------------------------+ - | sg | Golomb Rice coded signed scalar symbol | - | | coded with the method described in Signed | - | | Golomb Rice Codes (#golomb-rice-mode) | - +--------+-------------------------------------------+ - | br | Range coded Boolean (1-bit) symbol with | - | | the method described in Range binary | - | | values (#range-binary-values) | - +--------+-------------------------------------------+ + +--------+----------------------------------------------+ + | sg | Golomb Rice coded signed scalar symbol coded | + | | with the method described in Section 3.8.2 | + +--------+----------------------------------------------+ + | br | Range coded Boolean (1-bit) symbol with the | + | | method described in Section 3.8.1.1 | + +--------+----------------------------------------------+ | ur | Range coded unsigned scalar symbol coded | - | | with the method described in Range non | - | | binary values (#range-non-binary-values) | - +--------+-------------------------------------------+ - | sr | Range coded signed scalar symbol coded | - | | with the method described in Range non | - | | binary values (#range-non-binary-values) | - +--------+-------------------------------------------+ + | | with the method described in Section 3.8.1.2 | + +--------+----------------------------------------------+ + | sr | Range coded signed scalar symbol coded with | + | | the method described in Section 3.8.1.2 | + +--------+----------------------------------------------+ - Table 4 + Table 4: Definition of pseudo-code symbols for this + document. The same context that is initialized to 128 is used for all fields in the header. The following MUST be provided by external means during initialization of the decoder: "frame_pixel_width" is defined as "Frame" width in "Pixels". "frame_pixel_height" is defined as "Frame" height in "Pixels". @@ -1127,22 +1127,21 @@ Default values at the decoder initialization phase: "ConfigurationRecordIsPresent" is set to 0. 4.1. Parameters The "Parameters" section contains significant characteristics about the decoding configuration used for all instances of "Frame" (in FFV1 version 0 and 1) or the whole FFV1 bitstream (other versions), including the stream version, color configuration, and quantization - tables. The pseudo-code below describes the contents of the - bitstream. + tables. Figure 19 describes the contents of the bitstream. pseudo-code | type --------------------------------------------------------------|----- Parameters( ) { | version | ur if (version >= 3) { | micro_version | ur } | coder_type | ur if (coder_type > 1) { | @@ -1175,20 +1174,22 @@ initial_state_delta[ i ][ j ][ k ] | sr } | } | } | } | ec | ur intra | ur } | } | + Figure 19: A pseudo-code description of the bitstream contents. + CONTEXT_SIZE is 32. 4.1.1. version "version" specifies the version of the FFV1 bitstream. Each version is incompatible with other versions: decoders SHOULD reject a file due to an unknown version. Decoders SHOULD reject a file with version <= 1 && @@ -1235,39 +1236,42 @@ +-------+-------------------------+ | value | micro_version | +=======+=========================+ | 0...3 | reserved* | +-------+-------------------------+ | 4 | first stable variant | +-------+-------------------------+ | Other | reserved for future use | +-------+-------------------------+ - Table 6 + Table 6: The definitions for + micro_version values. * development versions may be incompatible with the stable variants. Meaning of micro_version for version 4 (note: at the time of writing of this specification, version 4 is not considered stable so the first stable version value is to be announced in the future): +---------+-------------------------+ | value | micro_version | +=========+=========================+ | 0...TBA | reserved* | +---------+-------------------------+ | TBA | first stable variant | +---------+-------------------------+ | Other | reserved for future use | +---------+-------------------------+ - Table 7 + Table 7: The definitions for + micro_version values for FFV1 + version 4. * development versions which may be incompatible with the stable variants. 4.1.3. coder_type "coder_type" specifies the coder used. +-------+-------------------------------------------------+ | value | coder used | @@ -1422,26 +1426,26 @@ Table 13 4.1.15. initial_state_delta "initial_state_delta[ i ][ j ][ k ]" indicates the initial Range coder state, it is encoded using "k" as context index and pred = j ? initial_states[ i ][j - 1][ k ] - Figure 15 + Figure 20 initial_state[ i ][ j ][ k ] = ( pred + initial_state_delta[ i ][ j ][ k ] ) & 255 - Figure 16 + Figure 21 4.1.16. ec "ec" indicates the error detection/correction type. +-------+--------------------------------------------+ | value | error detection/correction type | +=======+============================================+ | 0 | 32-bit CRC on the global header | +-------+--------------------------------------------+ @@ -1658,25 +1662,25 @@ of the specification and may have a significance in a later revision of this specification. Encoders SHOULD NOT fill these bits. Decoders SHOULD ignore these bits. Note in case these bits are used in a later revision of this specification: any revision of this specification SHOULD care about avoiding to add 40 bits of content after "SliceContent" for version 0 - and 1 of the bitstream. Background: due to some non conforming - encoders, some bitstreams where found with 40 extra bits - corresponding to "error_status" and "slice_crc_parity", a decoder - conforming to the revised specification could not do the difference - between a revised bitstream and a buggy bitstream. + and 1 of the bitstream. Background: Due to some non-conforming + encoders, some bitstreams were found with 40 extra bits corresponding + to "error_status" and "slice_crc_parity". As a result, a decoder + conforming to the revised specification could not distinguish between + a revised bitstream and a buggy bitstream. 4.5. Slice Header A "Slice Header" provides information about the decoding configuration of the "Slice", such as its spatial position, size, and aspect ratio. The pseudo-code below describes the contents of the "Slice Header". pseudo-code | type --------------------------------------------------------------|----- @@ -1909,21 +1913,21 @@ "slice_pixel_x" is the slice horizontal position in "Pixels". Its value is "floor( slice_x * frame_pixel_width / num_h_slices )". 4.7.4. sample_difference "sample_difference[ p ][ y ][ x ]" is the sample difference for "Sample" at "Plane" "p", y position "y", and x position "x". The "Sample" value is computed based on median predictor and context - described in the section on Samples (#samples). + described in Section 3.2. 4.8. Slice Footer A "Slice Footer" provides information about slice size and (optionally) parity. The pseudo-code below describes the contents of the "Slice Footer". Note: "Slice Footer" is always byte aligned. pseudo-code | type @@ -1970,26 +1974,26 @@ This is equivalent to storing the crc remainder in the 32-bit parity. The CRC generator polynomial used is the standard IEEE CRC polynomial (0x104C11DB7), with initial value 0, without pre-inversion and without post-inversion. 4.9. Quantization Table Set The Quantization Table Sets are stored by storing the number of equal entries -1 of the first half of the table (represented as "len - 1" - in the pseudo-code below) using the method described in Range Non - Binary Values (#range-non-binary-values). The second half doesn't - need to be stored as it is identical to the first with flipped sign. - "scale" and "len_count[ i ][ j ]" are temporary values used for the - computing of "context_count[ i ]" and are not used outside - Quantization Table Set pseudo-code. + in the pseudo-code below) using the method described in + Section 3.8.1.2. The second half doesn't need to be stored as it is + identical to the first with flipped sign. "scale" and "len_count[ i + ][ j ]" are temporary values used for the computing of + "context_count[ i ]" and are not used outside Quantization Table Set + pseudo-code. Example: Table: 0 0 1 1 1 1 2 2 -2 -2 -2 -1 -1 -1 -1 0 Stored values: 1, 3, 1 pseudo-code | type --------------------------------------------------------------|----- QuantizationTableSet( i ) { | scale = 1 | @@ -2108,49 +2112,47 @@ Subtype name: FFV1 Required parameters: None. Optional parameters: This parameter is used to signal the capabilities of a receiver implementation. This parameter MUST NOT be used for any other purpose. - version: The version of the FFV1 encoding as defined by the section - on version (#version). + version: The version of the FFV1 encoding as defined by + Section 4.1.1. micro_version: The micro_version of the FFV1 encoding as defined by - the section on micro_version (#micro-version). + Section 4.1.2. - coder_type: The coder_type of the FFV1 encoding as defined by the - section on coder_type (#coder-type). + coder_type: The coder_type of the FFV1 encoding as defined by + Section 4.1.3. colorspace_type: The colorspace_type of the FFV1 encoding as defined - by the section on colorspace_type (#colorspace-type). + by Section 4.1.5. bits_per_raw_sample: The bits_per_raw_sample of the FFV1 encoding as - defined by the section on bits_per_raw_sample (#bits-per-raw-sample). + defined by Section 4.1.7. max-slices: The value of max-slices is an integer indicating the maximum count of slices with a frames of the FFV1 encoding. Encoding considerations: This media type is defined for encapsulation in several audiovisual - container formats and contains binary data; see the section on - "Mapping FFV1 into Containers" (#mapping-ffv1-into-containers). This + container formats and contains binary data; see Section 4.2.3. This media type is framed binary data Section 4.8 of [RFC6838]. Security considerations: - See the "Security Considerations" section (#security-considerations) - of this document. + See Section 6 of this document. Interoperability considerations: None. Published specification: [I-D.ietf-cellar-ffv1] and RFC XXXX. [RFC Editor: Upon publication as an RFC, please replace "XXXX" with the number assigned to this document and remove this note.] @@ -2172,22 +2174,21 @@ Restrictions on usage: None. Author: Dave Rice dave@dericed.com (mailto:dave@dericed.com) Change controller: IETF cellar working group delegated from the IESG. 8. IANA Considerations The IANA is requested to register the following values: - * Media type registration as described in Media Type Definition - (#media-type-definition). + * Media type registration as described in Section 7. 9. Appendixes 9.1. Decoder implementation suggestions 9.1.1. Multi-threading Support and Independence of Slices 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 each slice. Each slice footer contains a slice_size field so the @@ -2205,107 +2206,115 @@ coherent...) or if there is no possibility of seeking into the stream. 10. Changelog See https://github.com/FFmpeg/FFV1/commits/master (https://github.com/FFmpeg/FFV1/commits/master) 11. Normative References - [I-D.ietf-cellar-ffv1] - Niedermayer, M., Rice, D., and J. Martinez, "FFV1 Video - Coding Format Version 0, 1, and 3", Work in Progress, - Internet-Draft, draft-ietf-cellar-ffv1-09, 6 September - 2019, - . - - [ISO.15444-1.2016] - International Organization for Standardization, - "Information technology -- JPEG 2000 image coding system: - Core coding system", October 2016. + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC + 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, + May 2017, . - [ISO.9899.1990] - International Organization for Standardization, - "Programming languages - C", 1990. + [Matroska] IETF, "Matroska", 2019, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet Denial-of-Service Considerations", RFC 4732, DOI 10.17487/RFC4732, December 2006, . + [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type + Specifications and Registration Procedures", BCP 13, + RFC 6838, DOI 10.17487/RFC6838, January 2013, + . + + [ISO.9899.2018] + International Organization for Standardization, + "Programming languages - C", 2018. + + [ISO.15444-1.2016] + International Organization for Standardization, + "Information technology -- JPEG 2000 image coding system: + Core coding system", October 2016. + + [ISO.9899.1990] + International Organization for Standardization, + "Programming languages - C", 1990. + [RFC4855] Casner, S., "Media Type Registration of RTP Payload Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007, . + [I-D.ietf-cellar-ffv1] + Niedermayer, M., Rice, D., and J. Martinez, "FFV1 Video + Coding Format Version 0, 1, and 3", Work in Progress, + Internet-Draft, draft-ietf-cellar-ffv1-11, 23 October + 2019, + . + [RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716, September 2012, . - [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type - Specifications and Registration Procedures", BCP 13, - RFC 6838, DOI 10.17487/RFC6838, January 2013, - . - 12. Informative References - [Address-Sanitizer] - The Clang Team, "ASAN AddressSanitizer website", undated, - . - - [AVI] Microsoft, "AVI RIFF File Reference", undated, - . - - [HuffYUV] Rudiak-Gould, B., "HuffYUV", December 2003, - . - [ISO.14495-1.1999] International Organization for Standardization, "Information technology -- Lossless and near-lossless compression of continuous-tone still images: Baseline", December 1999. - [ISO.14496-10.2014] - International Organization for Standardization, - "Information technology -- Coding of audio-visual objects - -- Part 10: Advanced Video Coding", September 2014. + [AVI] Microsoft, "AVI RIFF File Reference", undated, + . [ISO.14496-12.2015] International Organization for Standardization, "Information technology -- Coding of audio-visual objects -- Part 12: ISO base media file format", December 2015. - [Matroska] IETF, "Matroska", 2016, . + [REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the + FFV1 codec in FFmpeg", undated, . + + [YCbCr] Wikipedia, "YCbCr", undated, + . + + [HuffYUV] Rudiak-Gould, B., "HuffYUV", December 2003, + . + + [VALGRIND] Valgrind Developers, "Valgrind website", undated, + . + + [Address-Sanitizer] + The Clang Team, "ASAN AddressSanitizer website", undated, + . [NUT] Niedermayer, M., "NUT Open Container Format", December 2013, . [range-coding] Nigel, G. and N. Martin, "Range encoding: an algorithm for removing redundancy from a digitised message.", July 1979. - [REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the - FFV1 codec in FFmpeg", undated, . - - [VALGRIND] Valgrind Developers, "Valgrind website", undated, - . - - [YCbCr] Wikipedia, "YCbCr", undated, - . + [ISO.14496-10.2014] + International Organization for Standardization, + "Information technology -- Coding of audio-visual objects + -- Part 10: Advanced Video Coding", September 2014. Authors' Addresses Michael Niedermayer Email: michael@niedermayer.cc Dave Rice Email: dave@dericed.com