--- 1/draft-ietf-cellar-ffv1-v4-14.txt 2020-10-07 10:13:11.065984154 -0700
+++ 2/draft-ietf-cellar-ffv1-v4-15.txt 2020-10-07 10:13:11.169986794 -0700
@@ -1,20 +1,20 @@
cellar M. Niedermayer
Internet-Draft
Intended status: Standards Track D. Rice
-Expires: 22 February 2021
+Expires: 10 April 2021
J. Martinez
- 21 August 2020
+ 7 October 2020
FFV1 Video Coding Format Version 4
- draft-ietf-cellar-ffv1-v4-14
+ draft-ietf-cellar-ffv1-v4-15
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
@@ -25,21 +25,21 @@
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 22 February 2021.
+ This Internet-Draft will expire on 10 April 2021.
Copyright Notice
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
@@ -47,107 +47,107 @@
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Notation and Conventions . . . . . . . . . . . . . . . . . . 4
2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 5
- 2.2.1. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 5
+ 2.2.1. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 6
2.2.2. Arithmetic Operators . . . . . . . . . . . . . . . . 6
- 2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 6
+ 2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 7
2.2.4. Comparison Operators . . . . . . . . . . . . . . . . 7
2.2.5. Mathematical Functions . . . . . . . . . . . . . . . 7
2.2.6. Order of Operation Precedence . . . . . . . . . . . . 8
- 2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 8
- 2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 8
+ 2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 9
+ 2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 9
2.2.9. Bitstream Functions . . . . . . . . . . . . . . . . . 9
3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 9
- 3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 9
+ 3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3. Median Predictor . . . . . . . . . . . . . . . . . . . . 11
3.4. Quantization Table Sets . . . . . . . . . . . . . . . . . 12
3.5. Context . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 12
3.7. Color spaces . . . . . . . . . . . . . . . . . . . . . . 13
3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 13
- 3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 13
+ 3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.8. Coding of the Sample Difference . . . . . . . . . . . . . 15
3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 15
- 3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 21
- 4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 26
- 4.1. Quantization Table Set . . . . . . . . . . . . . . . . . 27
- 4.1.1. quant_tables . . . . . . . . . . . . . . . . . . . . 28
- 4.1.2. context_count . . . . . . . . . . . . . . . . . . . . 29
- 4.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 29
- 4.2.1. version . . . . . . . . . . . . . . . . . . . . . . . 31
- 4.2.2. micro_version . . . . . . . . . . . . . . . . . . . . 31
- 4.2.3. coder_type . . . . . . . . . . . . . . . . . . . . . 32
- 4.2.4. state_transition_delta . . . . . . . . . . . . . . . 33
- 4.2.5. colorspace_type . . . . . . . . . . . . . . . . . . . 33
- 4.2.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 34
- 4.2.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 34
- 4.2.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 35
- 4.2.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 35
- 4.2.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 35
- 4.2.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 35
- 4.2.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 36
- 4.2.13. quant_table_set_count . . . . . . . . . . . . . . . . 36
- 4.2.14. states_coded . . . . . . . . . . . . . . . . . . . . 36
- 4.2.15. initial_state_delta . . . . . . . . . . . . . . . . . 36
- 4.2.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 37
- 4.2.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 37
- 4.3. Configuration Record . . . . . . . . . . . . . . . . . . 37
- 4.3.1. reserved_for_future_use . . . . . . . . . . . . . . . 38
- 4.3.2. configuration_record_crc_parity . . . . . . . . . . . 38
- 4.3.3. Mapping FFV1 into Containers . . . . . . . . . . . . 38
- 4.4. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 39
- 4.5. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 41
- 4.6. Slice Header . . . . . . . . . . . . . . . . . . . . . . 42
- 4.6.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 42
- 4.6.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 42
- 4.6.3. slice_width . . . . . . . . . . . . . . . . . . . . . 42
- 4.6.4. slice_height . . . . . . . . . . . . . . . . . . . . 43
- 4.6.5. quant_table_set_index_count . . . . . . . . . . . . . 43
- 4.6.6. quant_table_set_index . . . . . . . . . . . . . . . . 43
- 4.6.7. picture_structure . . . . . . . . . . . . . . . . . . 43
- 4.6.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 44
- 4.6.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 44
- 4.6.10. reset_contexts . . . . . . . . . . . . . . . . . . . 44
- 4.6.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 44
- 4.7. Slice Content . . . . . . . . . . . . . . . . . . . . . . 45
- 4.7.1. primary_color_count . . . . . . . . . . . . . . . . . 45
- 4.7.2. plane_pixel_height . . . . . . . . . . . . . . . . . 45
- 4.7.3. slice_pixel_height . . . . . . . . . . . . . . . . . 46
- 4.7.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 46
- 4.8. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 46
- 4.8.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 46
- 4.8.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 47
- 4.8.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 47
- 4.8.4. sample_difference . . . . . . . . . . . . . . . . . . 47
- 4.9. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 47
- 4.9.1. slice_size . . . . . . . . . . . . . . . . . . . . . 48
- 4.9.2. error_status . . . . . . . . . . . . . . . . . . . . 48
- 4.9.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 48
- 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 48
- 6. Security Considerations . . . . . . . . . . . . . . . . . . . 49
- 7. Media Type Definition . . . . . . . . . . . . . . . . . . . . 50
- 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 51
- 9. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 51
- 10. Normative References . . . . . . . . . . . . . . . . . . . . 51
- 11. Informative References . . . . . . . . . . . . . . . . . . . 52
- Appendix A. Multi-theaded decoder implementation suggestions . . 54
+ 3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 22
+ 4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 28
+ 4.1. Quantization Table Set . . . . . . . . . . . . . . . . . 29
+ 4.1.1. quant_tables . . . . . . . . . . . . . . . . . . . . 30
+ 4.1.2. context_count . . . . . . . . . . . . . . . . . . . . 31
+ 4.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 31
+ 4.2.1. version . . . . . . . . . . . . . . . . . . . . . . . 33
+ 4.2.2. micro_version . . . . . . . . . . . . . . . . . . . . 33
+ 4.2.3. coder_type . . . . . . . . . . . . . . . . . . . . . 34
+ 4.2.4. state_transition_delta . . . . . . . . . . . . . . . 35
+ 4.2.5. colorspace_type . . . . . . . . . . . . . . . . . . . 35
+ 4.2.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 36
+ 4.2.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 36
+ 4.2.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 37
+ 4.2.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 37
+ 4.2.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 37
+ 4.2.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 37
+ 4.2.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 38
+ 4.2.13. quant_table_set_count . . . . . . . . . . . . . . . . 38
+ 4.2.14. states_coded . . . . . . . . . . . . . . . . . . . . 38
+ 4.2.15. initial_state_delta . . . . . . . . . . . . . . . . . 38
+ 4.2.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 39
+ 4.2.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 39
+ 4.3. Configuration Record . . . . . . . . . . . . . . . . . . 39
+ 4.3.1. reserved_for_future_use . . . . . . . . . . . . . . . 40
+ 4.3.2. configuration_record_crc_parity . . . . . . . . . . . 40
+ 4.3.3. Mapping FFV1 into Containers . . . . . . . . . . . . 40
+ 4.4. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 41
+ 4.5. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 43
+ 4.6. Slice Header . . . . . . . . . . . . . . . . . . . . . . 44
+ 4.6.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 44
+ 4.6.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 44
+ 4.6.3. slice_width . . . . . . . . . . . . . . . . . . . . . 44
+ 4.6.4. slice_height . . . . . . . . . . . . . . . . . . . . 45
+ 4.6.5. quant_table_set_index_count . . . . . . . . . . . . . 45
+ 4.6.6. quant_table_set_index . . . . . . . . . . . . . . . . 45
+ 4.6.7. picture_structure . . . . . . . . . . . . . . . . . . 45
+ 4.6.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 46
+ 4.6.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 46
+ 4.6.10. reset_contexts . . . . . . . . . . . . . . . . . . . 46
+ 4.6.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 46
+ 4.7. Slice Content . . . . . . . . . . . . . . . . . . . . . . 47
+ 4.7.1. primary_color_count . . . . . . . . . . . . . . . . . 47
+ 4.7.2. plane_pixel_height . . . . . . . . . . . . . . . . . 47
+ 4.7.3. slice_pixel_height . . . . . . . . . . . . . . . . . 48
+ 4.7.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 48
+ 4.8. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 48
+ 4.8.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 48
+ 4.8.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 49
+ 4.8.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 49
+ 4.8.4. sample_difference . . . . . . . . . . . . . . . . . . 49
+ 4.9. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 49
+ 4.9.1. slice_size . . . . . . . . . . . . . . . . . . . . . 50
+ 4.9.2. error_status . . . . . . . . . . . . . . . . . . . . 50
+ 4.9.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 50
+ 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 50
+ 6. Security Considerations . . . . . . . . . . . . . . . . . . . 51
+ 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52
+ 7.1. Media Type Definition . . . . . . . . . . . . . . . . . . 52
+ 8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 53
+ 9. Normative References . . . . . . . . . . . . . . . . . . . . 53
+ 10. Informative References . . . . . . . . . . . . . . . . . . . 54
+ Appendix A. Multi-theaded decoder implementation suggestions . . 55
Appendix B. Future handling of some streams created by non
- conforming encoders . . . . . . . . . . . . . . . . . . . 54
- Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54
+ conforming encoders . . . . . . . . . . . . . . . . . . . 56
+ Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 56
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
@@ -170,73 +170,81 @@
2. Notation and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"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 Section 4.4) and
+ "FFV1": choosen name of this video encoding format, short version of
+ "FF Video 1", the letters "FF" coming from "FFmpeg", the name of the
+ reference decoder, whose the first letters originaly means "Fast
+ Forward".
+
+ "Container": Format that encapsulates Frames (see Section 4.4) 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
+ component or a luma component in a Frame. Examples of Sample are
Luma (Y), Blue-difference Chroma (Cb), Red-difference Chroma (Cr),
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.
+ "Symbol": A value stored in the bitstream, which is defined and
+ decoded through one of the methods described in Table 4.
+
+ "Line": A discrete component of a static image composed of Samples
+ that represent a specific quantification of Samples of that image.
+
+ "Plane": A discrete component of a static image composed of Lines
+ that represent a specific quantification of Lines of that image.
"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.
- "ESC": An ESCape symbol to indicate that the symbol to be stored is
+ "ESC": An ESCape Symbol to indicate that the Symbol to be stored is
too large for normal storage and that an alternate storage method is
used.
"MSB": Most Significant Bit, the bit that can cause the largest
- change in magnitude of the symbol.
+ change in magnitude of the Symbol.
"VLC": Variable Length Code, a code that maps source symbols to a
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.
- "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) and the chroma of the "Pixel" (Cb and Cr). YCbCr word is used
- for historical reasons and currently references any color space
- relying on 1 luma "Sample" and 2 chroma "Samples", e.g. YCbCr, YCgCo
- or ICtCp. The exact meaning of the three numeric values is
- unspecified.
+ "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)
+ and the chroma of the Pixel (Cb and Cr). YCbCr word is used for
+ historical reasons and currently references any color space relying
+ on 1 luma Sample and 2 chroma Samples, e.g. YCbCr, YCgCo or ICtCp.
+ The exact meaning of the three numeric values is unspecified.
"TBA": To Be Announced. Used in reference to the development of
future iterations of the FFV1 specification.
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"
+ language [ISO.9899.2018] and uses its "if/else", "while" and "for"
keywords as well as functions defined within this document.
In some instances, pseudo-code is presented in a two-column format
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.
pseudo-code | type
--------------------------------------------------------------|-----
ExamplePseudoCode( ) { |
value | ur
} |
Figure 1: A depiction of type-labelled pseudo-code used within
this document.
@@ -280,57 +288,57 @@
"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.
2.2.4. Comparison Operators
- "a > b" means a is greater than b.
+ "a > b" is true when a is greater than b.
- "a >= b" means a is greater than or equal to b.
+ "a >= b" is true when a is greater than or equal to b.
- "a < b" means a is less than b.
+ "a < b" is true when a is less than b.
- "a <= b" means a is less than or equal b.
+ "a <= b" is true when a is less than or equal b.
- "a == b" means a is equal to b.
+ "a == b" is true when a is equal to b.
- "a != b" means a is not equal to b.
+ "a != b" is true when a is not equal to b.
- "a && b" means Boolean logical "and" of a and b.
+ "a && b" is true when both a is true and b is true.
- "a || b" means Boolean logical "or" of a and b.
+ "a || b" is true when either a is true or b is true.
- "!a" means Boolean logical "not" of a.
+ "!a" is true when a is not true.
"a ? b : c" if a is true, then b, otherwise c.
2.2.5. Mathematical Functions
"floor(a)" means the largest integer less 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
if a > 0 then 1, else 0.
"abs(a)" means the absolute value of a, i.e. "abs(a)" = "sign(a) *
a".
"log2(a)" means the base-two logarithm of a.
- "min(a,b)" means the smallest of two values a and b.
+ "min(a,b)" means the smaller of two values a and b.
- "max(a,b)" means the largest 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,
b, and c, i.e. a+b+c-min(a,b,c)-max(a,b,c).
"A <== B" means B implies A.
"A <==> B" means A <== B , B <== A.
a_(b) means the b-th value of a sequence of a
@@ -340,98 +348,97 @@
When order of precedence is not indicated explicitly by use of
parentheses, operations are evaluated in the following order (from
top to bottom, operations of same precedence being evaluated from
left to right). This order of operations is based on the order of
operations used in Standard C.
a++, a--
!a, -a
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, a >= b
a == b, a != b
a & b
a | b
a && b
a || b
a ? b : c
a = b, a += b, a -= b, a *= b
2.2.7. Range
- "a...b" means any value starting from a to b, inclusive.
+ "a...b" means any value 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
+ relies on its Container to store the "NumBytes" values; see
Section 4.3.3.
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.
+ "remaining_bits_in_bitstream( NumBytes )" 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.
2.2.9.2. remaining_symbols_in_syntax
"remaining_symbols_in_syntax( )" is true as long as the RangeCoder
has not consumed all the given input bytes.
2.2.9.3. byte_aligned
"byte_aligned( )" is true if "remaining_bits_in_bitstream( NumBytes
)" 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 Section 4.5) 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
+ For each "Slice" (as described in Section 4.5) 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 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
+ * 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"
+ * 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"
- 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 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 |
@@ -439,67 +446,67 @@
| 0 | a | | d | e | f | | f |
+---+---+---+---+---+---+---+---+
| 0 | d | | g | h | i | | i |
+---+---+---+---+---+---+---+---+
Figure 2: 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 Figure 3. The labels for these
- relatively positioned "Samples" are used within the median predictor
- and context.
+ 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 Figure 3. The labels for these relatively
+ positioned Samples are used within the median predictor and context.
+---+---+---+---+
| | | T | |
+---+---+---+---+
| |tl | t |tr |
+---+---+---+---+
| L | l | X | |
+---+---+---+---+
- Figure 3: A depiction of how relatively positions Samples are
- references within this document.
+ Figure 3: A depiction of how relatively positioned Samples are
+ 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.
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
this equation:
median(l, t, l + t - tl)
Note, this prediction template is also used in [ISO.14495-1.1999] and
[HuffYUV].
Exception for the median predictor: if "colorspace_type == 0 &&
- bits_per_raw_sample == 16 && ( coder_type == 1 || coder_type == 2 )",
- the following median predictor MUST be used:
+ bits_per_raw_sample == 16 && ( coder_type == 1 || coder_type == 2 )"
+ (see Section 4.2.5, Section 4.2.7 and Section 4.2.5), the following
+ median predictor MUST be used:
median(left16s, top16s, left16s + top16s - diag16s)
where:
left16s = l >= 32768 ? ( l - 65536 ) : l
top16s = t >= 32768 ? ( t - 65536 ) : t
diag16s = tl >= 32768 ? ( tl - 65536 ) : tl
- Background: a two's complement signed 16-bit signed integer was used
- for storing "Sample" values in all known implementations of FFV1
- bitstream. So in some circumstances, the most significant bit was
- wrongly interpreted (used as a sign bit instead of the 16th bit of an
+ Background: a two's complement 16-bit signed integer was used for
+ storing Sample values in all known implementations of FFV1 bitstream.
+ So in some circumstances, the most significant 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, the only
configuration of all known implementations being impacted is 16-bit
YCbCr with no Pixel transformation with Range Coder coder, as other
potentially impacted configurations (e.g. 15/16-bit JPEG2000-RCT with
Range Coder coder, or 16-bit content with Golomb Rice coder) were
implemented nowhere [ISO.15444-1.2016]. In the meanwhile, 16-bit
JPEG2000-RCT with Range Coder coder was implemented without this
issue in one implementation and validated by one conformance checker.
It is expected (to be confirmed) to remove this exception for the
median predictor in the next version of the FFV1 bitstream.
@@ -517,101 +524,96 @@
Q_(j)[k] = quant_tables[i][j][k&255]
Figure 4
In this formula, "i" is the Quantization Table Set index, "j" is the
Quantized Table index, "k" the Quantized Sample Difference.
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", "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 5
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.
+ 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.
3.6. 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:
- * 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 Y Plane, "quant_table_set_index[ 0 ]" 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
Background: in first implementations of FFV1 bitstream, the index for
- Cb and Cr "Planes" was stored even if it is not used (chroma_planes
- set to 0), this index is kept for "version" <= 3 in order to keep
+ Cb and Cr Planes was stored even if it is not used (chroma_planes set
+ to 0), this index is kept for "version" <= 3 in order to keep
compatibility with FFV1 bitstreams in the wild.
3.7. Color spaces
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.
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 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 and for each "Plane", each "Sample" is encoded from
- left to right.
+ 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.
+ In JPEG2000-RCT for each Line from top to bottom, each Plane is coded
+ and for each Plane, each Sample is encoded from left to right.
3.7.1. YCbCr
- This color space allows 1 to 4 "Planes".
+ This color space allows 1 to 4 Planes.
- The Cb and Cr "Planes" are optional, but if used then MUST be used
- together. Omitting the Cb and Cr "Planes" codes the frames in
+ The Cb and Cr Planes are optional, but if used then MUST be used
+ together. Omitting the Cb and Cr Planes codes the frames in
grayscale 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, Transparency
* Y, Cb, Cr
* Y, Cb, Cr, Transparency
- 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" is used, then it MUST be coded last.
+ 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
+ is used, then it MUST be coded last.
3.7.2. RGB
- This color space allows 3 or 4 "Planes".
+ This color space allows 3 or 4 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,
- 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
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
@@ -626,91 +628,91 @@
Cr = r - b
Y = b +(Cb + Cr) >> 2
b = Y -(Cb + Cr) >> 2
r = Cr + b
g = Cb + b
Figure 7
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
+ 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.
Cb and Cr are positively offset by "1 << bits_per_raw_sample" after
the conversion from RGB to the modified YCbCr and are negatively
offseted by the same value before the conversion from the modified
YCbCr to RGB, in order to have only non-negative values after the
conversion.
- 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.
+ 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 comprise the following structure:
+ As an example, a Frame that is two Pixels wide and two Pixels 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
- to bottom, with values interleaved by "Lines" and stored in this
- order:
+ to 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)
Cb(2,2) Cr(1,2) Cr(2,2)
3.8. Coding of the Sample Difference
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
+ 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 8: Description of the coding of the Sample Difference in
the bitstream.
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].
+ G. Nigel 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 9
+ Figure 9: A formula of the read of a binary value in Range Binary
+ mode.
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))) AND
l_(i) = L_(i) - R_(i) + r_(i) AND
t_(i) = r_(i) <==
@@ -739,71 +741,116 @@
Figure 13
L_(0) = 2 ^ 8 * B_(0) + B_(1)
Figure 14
j_(0) = 2
Figure 15
+ range = 0xFF00;
+ end = 0;
+ low = get_bits(16);
+ if (low >= range) {
+ low = range;
+ end = 1;
+ }
+
+ Figure 16: A pseudo-code description of the initial states in
+ Range Binary mode.
+
+ refill() {
+ if (range < 256) {
+ range = range * 256;
+ low = low * 256;
+ if (!end) {
+ c.low += get_bits(8);
+ if (remaining_bits_in_bitstream( NumBytes ) == 0) {
+ end = 1;
+ }
+ }
+ }
+ }
+
+ Figure 17: A pseudo-code description of refilling the Range
+ Binary Value coder buffer.
+
+ get_rac(state) {
+ rangeoff = (range * state) / 256;
+ range -= rangeoff;
+ if (low < range) {
+ state = zero_state[state];
+ refill();
+ return 0;
+ } else {
+ low -= range;
+ state = one_state[state];
+ range = rangeoff;
+ refill();
+ return 1;
+ }
+ }
+ Figure 18: A pseudo-code description of the read of a binary
+ value in Range Binary mode.
+
3.8.1.1.1. Termination
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
appended without affecting the range coder output. This mode is
not used in FFV1.
* 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
the range decoder. This is generally one byte shorter than the
open mode.
* 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
coded bytestream by one byte. In "Sentinel mode", the end of the
- range coded bytestream is a binary symbol with state 129, which
- value SHALL be discarded. After reading this symbol, the range
+ range coded bytestream is a binary Symbol with state 129, which
+ value SHALL be discarded. After reading this Symbol, the range
decoder will have read one byte beyond the end of the range coded
bytestream. This way the byte position of the end can be
determined. Bytestreams written in "Sentinel mode" can be read in
"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 non-corrupted and be of value
0.
Above describes the range decoding. Encoding is defined as any
process which produces a decodable bytestream.
There are three places where range coder termination is needed in
FFV1. First is in the "Configuration Record", in this case the size
of the range coded bytestream is known and handled as "Closed mode".
Second is the switch from the "Slice Header" which is range coded to
Golomb coded slices as "Sentinel mode". Third is the end of range
coded Slices which need to terminate before the CRC at their end.
This can be handled as "Sentinel mode" or as "Closed mode" if the CRC
position has been determined.
3.8.1.2. Range Non Binary Values
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
+ 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
+ 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
- Figure 16.
+ Figure 19.
int get_symbol(RangeCoder *c, uint8_t *state, int is_signed) {
if (get_rac(c, state + 0) {
return 0;
}
int e = 0;
while (get_rac(c, state + 1 + min(e, 9)) { //1..10
e++;
}
@@ -817,44 +864,44 @@
return a;
}
if (get_rac(c, state + 11 + min(e, 10))) { //11..21
return -a;
} else {
return a;
}
}
- Figure 16: A pseudo-code description of the contexts of Range Non
+ Figure 19: A pseudo-code description of the contexts of Range Non
Binary Values.
"get_symbol" is used for the read out of "sample_difference"
indicated in Figure 8.
"get_rac" returns a boolean, computed from the bytestream as
- described in Section 3.8.1.1.
+ described in Figure 9 as a formula and in Figure 18 as pseudo-code.
3.8.1.3. Initial Values for the Context Model
- At keyframes all Range coder state variables are set to their initial
- state.
+ When "keyframe" (see Section 4.4) value is 1, 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 17
+ Figure 20
zero_state_(i) = 256 - one_state_(256-i)
- Figure 18
+ Figure 21
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,
@@ -882,21 +929,21 @@
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 Section 4.2.3) MUST be set
to 2 and the difference to the default MUST be stored in the
"Parameters", see Section 4.2. The reference implementation of FFV1
- in FFmpeg uses Figure 19 by default at the time of this writing when
+ in FFmpeg uses Figure 22 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,
@@ -917,53 +964,53 @@
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 19: Alternative state transition table for Range coding.
+ Figure 22: 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.
+ The end of the bitstream of the Frame is padded with 0-bits until 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 two
parts. The prefix stores the most significant bits and the suffix
stores the k least significant bits or stores the whole number in the
ESC case.
int get_ur_golomb(k) {
for (prefix = 0; prefix < 12; prefix++) {
if (get_bits(1)) {
return get_bits(k) + (prefix << k);
}
}
return get_bits(bits) + 11;
}
- Figure 20: A pseudo-code description of the read of an unsigned
+ Figure 23: A pseudo-code description of the read of an unsigned
integer in Golomb Rice mode.
int get_sr_golomb(k) {
v = get_ur_golomb(k);
if (v & 1) return - (v >> 1) - 1;
else return (v >> 1);
}
- Figure 21: A pseudo-code description of the read of a signed
+ Figure 24: A pseudo-code description of the read of a signed
integer in Golomb Rice mode.
3.8.2.1.1. Prefix
+================+=======+
| bits | value |
+================+=======+
| 1 | 0 |
+----------------+-------+
| 01 | 1 |
@@ -985,55 +1032,61 @@
+=========+========================================+
+=========+========================================+
| non ESC | the k least significant bits MSB first |
+---------+----------------------------------------+
| ESC | the value - 11, in MSB first order |
+---------+----------------------------------------+
Table 2
- "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
+ Table 3 shows practical examples of how Signed Golomb Rice Codes are
+ decoded based on the series of bits extracted from the bitstream as
+ described by the method above:
+
+=====+=======================+=======+
| k | bits | value |
+=====+=======================+=======+
| 0 | 1 | 0 |
+-----+-----------------------+-------+
| 0 | 001 | 2 |
+-----+-----------------------+-------+
| 2 | 1 00 | 0 |
+-----+-----------------------+-------+
| 2 | 1 10 | 2 |
+-----+-----------------------+-------+
| 2 | 01 01 | 5 |
+-----+-----------------------+-------+
| any | 000000000000 10000000 | 139 |
+-----+-----------------------+-------+
- Table 3
+ Table 3: Examples of decoded Signed
+ Golomb Rice Codes.
3.8.2.2. Run Mode
Run mode is entered when the context is 0 and left as soon as a non-0
- difference is found. The level is identical to the predicted one.
- The run and the first different level are coded.
+ difference is found. The sample difference is identical to the
+ predicted one. The run and the first different sample difference are
+ coded as defined in Section 3.8.2.4.1.
3.8.2.2.1. Run Length Coding
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"
that determines the number of bits in the less significant part of
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 for each Plane
and slice to 0.
log2_run[41] = {
0, 0, 0, 0, 1, 1, 1, 1,
2, 2, 2, 2, 3, 3, 3, 3,
4, 4, 5, 5, 6, 6, 7, 7,
8, 9,10,11,12,13,14,15,
16,17,18,19,20,21,22,23,
24,
};
@@ -1114,86 +1167,86 @@
-state->count + 1);
} else if (state->drift > 0) {
state->bias = min(state->bias + 1, 127);
state->drift = min(state->drift - state->count, 0);
}
return ret;
}
-3.8.2.4.1. Level Coding
+3.8.2.4.1. Golomb Rice Sample Difference Coding
Level coding is identical to the normal difference coding with the
exception that the 0 value is removed as it cannot occur:
diff = get_vlc_symbol(context_state);
if (diff >= 0) {
diff++;
}
Note, this is different from JPEG-LS, which doesn't use prediction in
run mode and uses a different encoding and context model for the last
- difference. On a small set of test "Samples" the use of prediction
+ difference. On a small set of test Samples the use of prediction
slightly improved the compression rate.
3.8.2.5. Initial Values for the VLC context state
- At keyframes all coder state variables are set to their initial
- state.
+ When "keyframe" (see Section 4.4) value is 1, all coder state
+ variables are set to their initial state.
drift = 0;
error_sum = 4;
bias = 0;
count = 1;
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".
- Within the following sub-sections, pseudo-code is used to explain the
- 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.
+ Within the following sub-sections, pseudo-code is used, as described
+ in Section 2.2.1, to explain the structure of each FFV1 bitstream
+ component. 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 |
+ +========+=================================================+
+ | u(n) | unsigned big endian integer Symbol using n bits |
+ +--------+-------------------------------------------------+
+ | 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 |
+ +--------+-------------------------------------------------+
+ | 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 Section 3.8.1.2 |
- +--------+----------------------------------------------+
- | sr | Range coded signed scalar symbol coded with |
+ +--------+-------------------------------------------------+
+ | ur | Range coded unsigned scalar Symbol coded with |
| | the method described in Section 3.8.1.2 |
- +--------+----------------------------------------------+
- | sd | Sample difference coded with the method |
+ +--------+-------------------------------------------------+
+ | sr | Range coded signed scalar Symbol coded with the |
+ | | method described in Section 3.8.1.2 |
+ +--------+-------------------------------------------------+
+ | sd | Sample difference Symbol coded with the method |
| | described in Section 3.8 |
- +--------+----------------------------------------------+
+ +--------+-------------------------------------------------+
Table 4: Definition of pseudo-code symbols for this
document.
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_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:
"ConfigurationRecordIsPresent" is set to 0.
4.1. 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
@@ -1253,24 +1306,24 @@
4.1.2. context_count
"context_count[ i ]" indicates the count of contexts for Quantization
Table Set "i". "context_count[ i ]" MUST be less than or equal to
32768.
4.2. Parameters
The "Parameters" section contains significant characteristics about
- the decoding configuration used for all instances of "Frame" (in FFV1
+ 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. Figure 22 describes the contents of the bitstream.
+ tables. Figure 25 describes the contents of the bitstream.
"Parameters" has its own initial states, all set to 128.
pseudo-code | type
--------------------------------------------------------------|-----
Parameters( ) { |
version | ur
if (version >= 3) { |
micro_version | ur
} |
@@ -1305,21 +1358,21 @@
initial_state_delta[ i ][ j ][ k ] | sr
} |
} |
} |
} |
ec | ur
intra | ur
} |
} |
- Figure 22: A pseudo-code description of the bitstream contents.
+ Figure 25: A pseudo-code description of the bitstream contents.
CONTEXT_SIZE is 32.
4.2.1. version
"version" specifies the version of the FFV1 bitstream.
Each version is incompatible with other versions: decoders SHOULD
reject FFV1 bitstreams due to an unknown version.
@@ -1435,99 +1488,97 @@
If "state_transition_delta" is not present in the FFV1 bitstream, all
Range coder custom state transition table elements are assumed to be
0.
4.2.5. colorspace_type
"colorspace_type" specifies the color space encoded, the pixel
transformation used by the encoder, the extra plane content, as well
as interleave method.
- +=======+=============+================+==============+=============+
+ +=======+==============+================+==============+============+
| value | color space | pixel | extra plane | interleave |
| | encoded | transformation | content | method |
- +=======+=============+================+==============+=============+
- | 0 | YCbCr | None | Transparency | "Plane" |
- | | | | | then |
- | | | | | "Line" |
- +-------+-------------+----------------+--------------+-------------+
- | 1 | RGB | JPEG2000-RCT | Transparency | "Line" |
- | | | | | then |
- | | | | | "Plane" |
- +-------+-------------+----------------+--------------+-------------+
+ +=======+==============+================+==============+============+
+ | 0 | YCbCr | None | Transparency | Plane then |
+ | | | | | Line |
+ +-------+--------------+----------------+--------------+------------+
+ | 1 | RGB | JPEG2000-RCT | Transparency | Line then |
+ | | | | | Plane |
+ +-------+--------------+----------------+--------------+------------+
| Other | reserved | reserved for | reserved for | reserved |
| | for future | future use | future use | for future |
| | use | | | use |
- +-------+-------------+----------------+--------------+-------------+
+ +-------+--------------+----------------+--------------+------------+
Table 9
FFV1 bitstreams with "colorspace_type" == 1 && ("chroma_planes" !=
1 || "log2_h_chroma_subsample" != 0 || "log2_v_chroma_subsample" !=
0) are not part of this specification.
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 |
- +=======+=================================+
- | 0 | chroma "Planes" are not present |
- +-------+---------------------------------+
- | 1 | chroma "Planes" are present |
- +-------+---------------------------------+
+ +=======+===============================+
+ | 0 | chroma Planes are not present |
+ +-------+-------------------------------+
+ | 1 | chroma Planes are present |
+ +-------+-------------------------------+
Table 10
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.
- +=======+===================================+
+ +=======+=================================+
| value | bits for each sample |
- +=======+===================================+
+ +=======+=================================+
| 0 | reserved* |
- +-------+-----------------------------------+
- | Other | the actual bits for each "Sample" |
- +-------+-----------------------------------+
+ +-------+---------------------------------+
+ | Other | the actual bits for each Sample |
+ +-------+---------------------------------+
Table 11
* Encoders MUST NOT store "bits_per_raw_sample" = 0. Decoders SHOULD
accept and interpret "bits_per_raw_sample" = 0 as 8.
4.2.8. log2_h_chroma_subsample
"log2_h_chroma_subsample" indicates the subsample factor, stored in
- powers to which the number 2 must be raised, between luma and chroma
- width ("chroma_width = 2 ^ -log2_h_chroma_subsample * luma_width").
+ powers to which the number 2 is raised, between luma and chroma width
+ ("chroma_width = 2 ^ -log2_h_chroma_subsample * luma_width").
4.2.9. log2_v_chroma_subsample
"log2_v_chroma_subsample" indicates the subsample factor, stored in
- powers to which the number 2 must be 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 *
luma_height").
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 |
- +=======+==============================+
- | 0 | extra "Plane" is not present |
- +-------+------------------------------+
- | 1 | extra "Plane" is present |
- +-------+------------------------------+
+ +=======+============================+
+ | 0 | extra Plane is not present |
+ +-------+----------------------------+
+ | 1 | extra Plane is present |
+ +-------+----------------------------+
Table 12
4.2.11. num_h_slices
"num_h_slices" indicates the number of horizontal elements of the
slice raster.
Inferred to be 1 if not present.
@@ -1565,91 +1616,91 @@
Table 13
4.2.15. 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 ] : 128
- Figure 23
+ Figure 26
initial_state[ i ][ j ][ k ] =
( pred + initial_state_delta[ i ][ j ][ k ] ) & 255
- Figure 24
+ Figure 27
4.2.16. ec
"ec" indicates the error detection/correction type.
+=======+=================================================+
| value | error detection/correction type |
+=======+=================================================+
| 0 | 32-bit CRC in "ConfigurationRecord" |
+-------+-------------------------------------------------+
| 1 | 32-bit CRC in "Slice" and "ConfigurationRecord" |
+-------+-------------------------------------------------+
| Other | reserved for future use |
+-------+-------------------------------------------------+
Table 14
4.2.17. intra
"intra" indicates the constraint on "keyframe" in each instance of
- "Frame".
+ Frame.
Inferred to be 0 if not present.
+=======+=======================================================+
| value | relationship |
+=======+=======================================================+
| 0 | "keyframe" can be 0 or 1 (non keyframes or keyframes) |
+-------+-------------------------------------------------------+
| 1 | "keyframe" MUST be 1 (keyframes only) |
+-------+-------------------------------------------------------+
| Other | reserved for future use |
+-------+-------------------------------------------------------+
Table 15
4.3. Configuration Record
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
- of "Frame". The size of the "Configuration Record", "NumBytes", is
- supplied by the underlying "Container".
+ of Frame. The size of the "Configuration Record", "NumBytes", is
+ supplied by the underlying Container.
pseudo-code | type
-----------------------------------------------------------|-----
ConfigurationRecord( NumBytes ) { |
ConfigurationRecordIsPresent = 1 |
Parameters( ) |
while (remaining_symbols_in_syntax(NumBytes - 4)) { |
reserved_for_future_use | br/ur/sr
} |
configuration_record_crc_parity | u(32)
} |
4.3.1. reserved_for_future_use
- "reserved_for_future_use" has semantics that are reserved for future
- use.
+ "reserved_for_future_use" is a placeholder for future updates of this
+ specification.
Encoders conforming to this version of this specification SHALL NOT
- write this value.
+ write "reserved_for_future_use".
Decoders conforming to this version of this specification SHALL
- ignore its value.
+ ignore "reserved_for_future_use".
4.3.2. configuration_record_crc_parity
"configuration_record_crc_parity" 32 bits that are chosen so that the
"Configuration Record" as a whole has a CRC remainder of 0.
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.
@@ -1699,42 +1750,42 @@
versions 2 or less, the Matroska "CodecPrivate" Element SHOULD NOT be
used. For FFV1 versions 3 or greater, the Matroska "CodecPrivate"
Element MUST contain the FFV1 "Configuration Record" structure and no
other data. See [Matroska] for more information about elements.
"NumBytes" is defined as the "Element Data Size" of the
"CodecPrivate" Element.
4.4. Frame
- A "Frame" is an encoded representation of a complete static image.
- The whole "Frame" is provided by the underlaying container.
+ A Frame is an encoded representation of a complete static image. The
+ whole Frame is provided by the underlaying container.
- A "Frame" consists of the "keyframe" field, "Parameters" (if
- "version" <= 1), and a sequence of independent slices. The pseudo-
- code below describes the contents of a "Frame".
+ A Frame consists of the "keyframe" field, "Parameters" (if "version"
+ <= 1), and a sequence of independent slices. The pseudo-code below
+ describes the contents of a Frame.
"keyframe" field has its own initial state, set to 128.
pseudo-code | type
--------------------------------------------------------------|-----
Frame( NumBytes ) { |
keyframe | br
if (keyframe && !ConfigurationRecordIsPresent { |
Parameters( ) |
} |
while (remaining_bits_in_bitstream( NumBytes )) { |
Slice( ) |
} |
} |
- Architecture overview of slices in a "Frame":
+ Architecture overview of slices in a Frame:
+=================================================================+
+=================================================================+
| first slice header |
+-----------------------------------------------------------------+
| first slice content |
+-----------------------------------------------------------------+
| first slice footer |
+-----------------------------------------------------------------+
| --------------------------------------------------------------- |
@@ -1755,25 +1806,24 @@
+-----------------------------------------------------------------+
| last slice content |
+-----------------------------------------------------------------+
| last slice footer |
+-----------------------------------------------------------------+
Table 16
4.5. Slice
- A "Slice" is an independent spatial sub-section of a "Frame" that is
- 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 the opportunities of multithreaded encoding and
- decoding.
+ A "Slice" is an independent spatial sub-section of a Frame that is
+ 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
+ the opportunities of multithreaded encoding and decoding.
A "Slice" consists of a "Slice Header" (when relevant), a "Slice
Content", and a "Slice Footer" (when relevant). The pseudo-code
below describes the contents of a "Slice".
pseudo-code | type
--------------------------------------------------------------|-----
Slice( ) { |
if (version >= 3) { |
SliceHeader( ) |
@@ -1794,23 +1844,23 @@
} |
} |
"padding" specifies a bit without any significance and used only for
byte alignment. MUST be 0.
"reserved" specifies a bit without any significance in this revision
of the specification and may have a significance in a later revision
of this specification.
- Encoders SHOULD NOT fill these bits.
+ Encoders SHOULD NOT fill "reserved".
- Decoders SHOULD ignore these bits.
+ Decoders SHOULD ignore "reserved".
4.6. 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".
"Slice Header" has its own initial states, all set to 128.
@@ -1872,21 +1922,21 @@
"quant_table_set_index" indicates the Quantization Table Set index to
select the Quantization Table Set and the initial states for the
"Slice Content".
Inferred to be 0 if not present.
4.6.7. picture_structure
"picture_structure" specifies the temporal and spatial relationship
- of each "Line" of the "Frame".
+ of each Line of the Frame.
Inferred to be 0 if not present.
+=======+=========================+
| value | picture structure used |
+=======+=========================+
| 0 | unknown |
+-------+-------------------------+
| 1 | top field first |
+-------+-------------------------+
@@ -1894,47 +1944,47 @@
+-------+-------------------------+
| 3 | progressive |
+-------+-------------------------+
| Other | reserved for future use |
+-------+-------------------------+
Table 17
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.
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 Sample aspect ratio is unknown.
If "sar_den" is 0, decoders SHOULD ignore the encoded value and
consider that "sar_num" is 0.
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.
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 Sample aspect ratio is unknown.
If "sar_num" is 0, decoders SHOULD ignore the encoded value and
consider that "sar_den" is 0.
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.
4.6.11. slice_coding_mode
"slice_coding_mode" indicates the slice coding mode.
Inferred to be 0 if not present.
+=======+=============================+
@@ -1944,24 +1994,24 @@
+-------+-----------------------------+
| 1 | raw PCM |
+-------+-----------------------------+
| Other | reserved for future use |
+-------+-----------------------------+
Table 18
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" then by row (YCbCr) or by row then by "Plane" (RGB).
+ Depending on the configuration, Line elements are ordered by Plane
+ then by row (YCbCr) or by row then by Plane (RGB).
pseudo-code | type
--------------------------------------------------------------|-----
SliceContent( ) { |
if (colorspace_type == 0) { |
for (p = 0; p < primary_color_count; p++) { |
for (y = 0; y < plane_pixel_height[ p ]; y++) { |
Line( p, y ) |
} |
} |
@@ -1975,22 +2025,22 @@
} |
4.7.1. primary_color_count
"primary_color_count" is defined as:
1 + ( chroma_planes ? 2 : 0 ) + ( extra_plane ? 1 : 0 )
4.7.2. plane_pixel_height
- "plane_pixel_height[ p ]" is the height in "Pixels" of "Plane" p of
- the "Slice". It is defined as:
+ "plane_pixel_height[ p ]" is the height in Pixels of Plane p of the
+ "Slice". It is defined as:
chroma_planes == 1 && (p == 1 || p == 2)
? ceil(slice_pixel_height / (1 << log2_v_chroma_subsample))
: slice_pixel_height
4.7.3. slice_pixel_height
"slice_pixel_height" is the height in pixels of the slice. It is
defined as:
@@ -2002,71 +2052,71 @@
4.7.4. slice_pixel_y
"slice_pixel_y" is the slice vertical position in pixels. It is
defined as:
floor( slice_y * frame_pixel_height / num_v_slices )
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
- describes the contents of the "Line".
+ describes the contents of the Line.
pseudo-code | type
--------------------------------------------------------------|-----
Line( p, y ) { |
if (colorspace_type == 0) { |
for (x = 0; x < plane_pixel_width[ p ]; x++) { |
sample_difference[ p ][ y ][ x ] | sd
} |
} else if (colorspace_type == 1) { |
for (x = 0; x < slice_pixel_width; x++) { |
sample_difference[ p ][ y ][ x ] | sd
} |
} |
} |
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:
chroma\_planes == 1 && (p == 1 || p == 2)
? ceil( slice_pixel_width / (1 << log2_h_chroma_subsample) )
: 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 as:
floor(
( slice_x + slice_width )
* slice_pixel_width
/ num_h_slices
) - 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:
floor( slice_x * frame_pixel_width / num_h_slices )
4.8.4. 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 Section 3.2.
+ Sample at Plane "p", y position "y", and x position "x". The Sample
+ value is computed based on median predictor and context described in
+ Section 3.2.
4.9. 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
@@ -2115,54 +2165,54 @@
The CRC generator polynomial used is the standard IEEE CRC polynomial
(0x104C11DB7), with initial value 0, without pre-inversion and
without post-inversion.
5. Restrictions
To ensure that fast multithreaded decoding is possible, starting with
version 3 and if "frame_pixel_width * frame_pixel_height" is more
than 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
- "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.
- 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
+ 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
slice overlapping).
- For each "Frame" with "keyframe" value of 0, each slice MUST have the
+ For each Frame with "keyframe" value of 0, each slice MUST have the
same value of "slice_x", "slice_y", "slice_width", "slice_height" as
- a slice in the previous "Frame", except if "reset_contexts" is 1.
+ a slice in the previous Frame, except if "reset_contexts" is 1.
6. Security Considerations
Like any other codec, (such as [RFC6716]), FFV1 should not be used
with insecure ciphers or cipher-modes that are vulnerable to known
plaintext attacks. Some of the header bits as well as the padding
are easily predictable.
Implementations of the FFV1 codec need to take appropriate security
considerations into account, as outlined in [RFC4732]. It is
extremely important for the decoder to be robust against malicious
- payloads. Malicious payloads must not cause the decoder to overrun
+ payloads. Malicious payloads MUST NOT cause the decoder to overrun
its allocated memory or to take an excessive amount of resources to
decode. 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
attack transcoding gateways. A frequent security problem in image
- and video codecs is also to not check for integer overflows, for
- example to allocate "frame_pixel_width * frame_pixel_height" in
- "Pixel" count computations without considering that the
- multiplication result may have overflowed the arithmetic types range.
- The range coder could, if implemented naively, read one byte over the
- end. The implementation must ensure that no read outside allocated
- and initialized memory occurs.
+ and video codecs is failure to check for integer overflows. An
+ example is allocating "frame_pixel_width * frame_pixel_height" in
+ Pixel count computations without considering that the multiplication
+ result may have overflowed the arithmetic types range. The range
+ coder could, if implemented naively, read one byte over the end. The
+ implementation MUST ensure that no read outside allocated and
+ initialized memory occurs.
None of the content carried in FFV1 is intended to be executable.
The reference implementation [REFIMPL] contains no known buffer
overflow or cases where a specially crafted packet or video segment
could cause a significant increase in CPU load.
The reference implementation [REFIMPL] was validated in the following
conditions:
@@ -2174,21 +2224,25 @@
then subjected to random corruption.
* Sending the decoder random packets that are not FFV1.
In all of the conditions above, the decoder and encoder was run
inside the [VALGRIND] memory debugger as well as clangs address
sanitizer [Address-Sanitizer], which track reads and writes to
invalid memory regions as well as the use of uninitialized memory.
There were no errors reported on any of the tested conditions.
-7. Media Type Definition
+7. IANA Considerations
+
+ The IANA is requested to register the following values:
+
+7.1. Media Type Definition
This registration is done using the template defined in [RFC6838] and
following [RFC4855].
Type name: video
Subtype name: FFV1
Required parameters: None.
@@ -2241,133 +2295,123 @@
Niedermayer michael@niedermayer.cc (mailto:michael@niedermayer.cc)
Intended usage: COMMON
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 Section 7.
-
-9. Changelog
+8. Changelog
See https://github.com/FFmpeg/FFV1/commits/master
(https://github.com/FFmpeg/FFV1/commits/master)
[RFC Editor: Please remove this Changelog section prior to
publication.]
-10. 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]
+ International Organization for Standardization,
+ "Programming languages - C", ISO Standard 9899, 2018.
+
+ [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,
.
- [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
- 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
- May 2017, .
-
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732,
DOI 10.17487/RFC4732, December 2006,
.
- [ISO.9899.2018]
- International Organization for Standardization,
- "Programming languages - C", ISO Standard 9899, 2018.
+ [RFC4855] Casner, S., "Media Type Registration of RTP Payload
+ Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
+ .
+
+ [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,
.
- [ISO.9899.1990]
- International Organization for Standardization,
- "Programming languages - C", ISO Standard 9899, 1990.
-
- [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, .
- [RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the
- Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716,
- September 2012, .
+10. Informative References
- [RFC4855] Casner, S., "Media Type Registration of RTP Payload
- Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
- .
+ [Address-Sanitizer]
+ The Clang Team, "ASAN AddressSanitizer website", undated,
+ .
- [Matroska] IETF, "Matroska", 2019, .
+ [AVI] Microsoft, "AVI RIFF File Reference", undated,
+ .
-11. Informative References
+ [HuffYUV] Rudiak-Gould, B., "HuffYUV", December 2003,
+ .
[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-ffv1-16, 2 July 2020,
- .
+ Internet-Draft, draft-ietf-cellar-ffv1-17, 21 August 2020,
+ .
[ISO.14495-1.1999]
International Organization for Standardization,
"Information technology -- Lossless and near-lossless
compression of continuous-tone still images: Baseline",
December 1999.
- [NUT] Niedermayer, M., "NUT Open Container Format", December
- 2013, .
-
- [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.
- [VALGRIND] Valgrind Developers, "Valgrind website", undated,
- .
-
- [REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the
- FFV1 codec in FFmpeg", undated, .
-
- [HuffYUV] Rudiak-Gould, B., "HuffYUV", December 2003,
- .
-
[ISO.14496-12.2015]
International Organization for Standardization,
"Information technology -- Coding of audio-visual objects
-- Part 12: ISO base media file format", December 2015.
+ [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.",
- Proceedings of the Conference on Video and Data
- Recording. Institution of Electronic and Radio Engineers,
- Hampshire, England, July 1979.
+ Martin, G. N. N., "Range encoding: an algorithm for
+ removing redundancy from a digitised message", Proceedings
+ of the Conference on Video and Data Recording. Institution
+ of Electronic and Radio Engineers, Hampshire, England,
+ July 1979.
- [AVI] Microsoft, "AVI RIFF File Reference", undated,
- .
+ [REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the
+ FFV1 codec in FFmpeg", undated, .
- [Address-Sanitizer]
- The Clang Team, "ASAN AddressSanitizer website", undated,
- .
+ [VALGRIND] Valgrind Developers, "Valgrind website", undated,
+ .
+
+ [YCbCr] Wikipedia, "YCbCr", undated,
+ .
Appendix A. Multi-theaded decoder implementation suggestions
This appendix is informative.
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
boundary of each slice is computable without having to parse the
slice content. That allows multi-threading as well as independence