draft-ietf-cellar-ffv1-17.txt   draft-ietf-cellar-ffv1-18.txt 
cellar M. Niedermayer cellar M. Niedermayer
Internet-Draft Internet-Draft
Intended status: Informational D. Rice Intended status: Informational D. Rice
Expires: 22 February 2021 Expires: 10 April 2021
J. Martinez J. Martinez
21 August 2020 7 October 2020
FFV1 Video Coding Format Version 0, 1, and 3 FFV1 Video Coding Format Version 0, 1, and 3
draft-ietf-cellar-ffv1-17 draft-ietf-cellar-ffv1-18
Abstract Abstract
This document defines FFV1, a lossless intra-frame video encoding This document defines FFV1, a lossless intra-frame video encoding
format. FFV1 is designed to efficiently compress video data in a format. FFV1 is designed to efficiently compress video data in a
variety of pixel formats. Compared to uncompressed video, FFV1 variety of pixel formats. Compared to uncompressed video, FFV1
offers storage compression, frame fixity, and self-description, which offers storage compression, frame fixity, and self-description, which
makes FFV1 useful as a preservation or intermediate video format. makes FFV1 useful as a preservation or intermediate video format.
Status of This Memo Status of This Memo
skipping to change at page 1, line 36 skipping to change at page 1, line 36
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This Internet-Draft will expire on 22 February 2021. This Internet-Draft will expire on 10 April 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Notation and Conventions . . . . . . . . . . . . . . . . . . 5 2. Notation and Conventions . . . . . . . . . . . . . . . . . . 5
2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 6 2.2.1. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 6
2.2.2. Arithmetic Operators . . . . . . . . . . . . . . . . 6 2.2.2. Arithmetic Operators . . . . . . . . . . . . . . . . 6
2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 7 2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 7
2.2.4. Comparison Operators . . . . . . . . . . . . . . . . 7 2.2.4. Comparison Operators . . . . . . . . . . . . . . . . 7
2.2.5. Mathematical Functions . . . . . . . . . . . . . . . 7 2.2.5. Mathematical Functions . . . . . . . . . . . . . . . 8
2.2.6. Order of Operation Precedence . . . . . . . . . . . . 8 2.2.6. Order of Operation Precedence . . . . . . . . . . . . 8
2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 9 2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 9
2.2.9. Bitstream Functions . . . . . . . . . . . . . . . . . 9 2.2.9. Bitstream Functions . . . . . . . . . . . . . . . . . 9
3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 9 3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3. Median Predictor . . . . . . . . . . . . . . . . . . . . 11 3.3. Median Predictor . . . . . . . . . . . . . . . . . . . . 11
3.4. Quantization Table Sets . . . . . . . . . . . . . . . . . 12 3.4. Quantization Table Sets . . . . . . . . . . . . . . . . . 12
3.5. Context . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.5. Context . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 12 3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 13
3.7. Color spaces . . . . . . . . . . . . . . . . . . . . . . 13 3.7. Color spaces . . . . . . . . . . . . . . . . . . . . . . 13
3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 13 3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 14
3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.8. Coding of the Sample Difference . . . . . . . . . . . . . 15 3.8. Coding of the Sample Difference . . . . . . . . . . . . . 16
3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 16 3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 16
3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 21 3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 22
4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1. Quantization Table Set . . . . . . . . . . . . . . . . . 27 4.1. Quantization Table Set . . . . . . . . . . . . . . . . . 29
4.1.1. quant_tables . . . . . . . . . . . . . . . . . . . . 28 4.1.1. quant_tables . . . . . . . . . . . . . . . . . . . . 30
4.1.2. context_count . . . . . . . . . . . . . . . . . . . . 29 4.1.2. context_count . . . . . . . . . . . . . . . . . . . . 31
4.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 29 4.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 31
4.2.1. version . . . . . . . . . . . . . . . . . . . . . . . 31 4.2.1. version . . . . . . . . . . . . . . . . . . . . . . . 33
4.2.2. micro_version . . . . . . . . . . . . . . . . . . . . 31 4.2.2. micro_version . . . . . . . . . . . . . . . . . . . . 33
4.2.3. coder_type . . . . . . . . . . . . . . . . . . . . . 32 4.2.3. coder_type . . . . . . . . . . . . . . . . . . . . . 34
4.2.4. state_transition_delta . . . . . . . . . . . . . . . 32 4.2.4. state_transition_delta . . . . . . . . . . . . . . . 34
4.2.5. colorspace_type . . . . . . . . . . . . . . . . . . . 33 4.2.5. colorspace_type . . . . . . . . . . . . . . . . . . . 35
4.2.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 33 4.2.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 35
4.2.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 34 4.2.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 36
4.2.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 34 4.2.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 36
4.2.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 34 4.2.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 36
4.2.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 34 4.2.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 36
4.2.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 35 4.2.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 37
4.2.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 35 4.2.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 37
4.2.13. quant_table_set_count . . . . . . . . . . . . . . . . 35 4.2.13. quant_table_set_count . . . . . . . . . . . . . . . . 37
4.2.14. states_coded . . . . . . . . . . . . . . . . . . . . 35 4.2.14. states_coded . . . . . . . . . . . . . . . . . . . . 37
4.2.15. initial_state_delta . . . . . . . . . . . . . . . . . 35 4.2.15. initial_state_delta . . . . . . . . . . . . . . . . . 37
4.2.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 36 4.2.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.2.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 36 4.2.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 38
4.3. Configuration Record . . . . . . . . . . . . . . . . . . 37 4.3. Configuration Record . . . . . . . . . . . . . . . . . . 39
4.3.1. reserved_for_future_use . . . . . . . . . . . . . . . 37 4.3.1. reserved_for_future_use . . . . . . . . . . . . . . . 39
4.3.2. configuration_record_crc_parity . . . . . . . . . . . 37 4.3.2. configuration_record_crc_parity . . . . . . . . . . . 39
4.3.3. Mapping FFV1 into Containers . . . . . . . . . . . . 37 4.3.3. Mapping FFV1 into Containers . . . . . . . . . . . . 39
4.4. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 38 4.4. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4.5. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.5. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.6. Slice Header . . . . . . . . . . . . . . . . . . . . . . 41 4.6. Slice Header . . . . . . . . . . . . . . . . . . . . . . 43
4.6.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 42 4.6.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 44
4.6.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 42 4.6.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 44
4.6.3. slice_width . . . . . . . . . . . . . . . . . . . . . 42 4.6.3. slice_width . . . . . . . . . . . . . . . . . . . . . 44
4.6.4. slice_height . . . . . . . . . . . . . . . . . . . . 42 4.6.4. slice_height . . . . . . . . . . . . . . . . . . . . 44
4.6.5. quant_table_set_index_count . . . . . . . . . . . . . 42 4.6.5. quant_table_set_index_count . . . . . . . . . . . . . 44
4.6.6. quant_table_set_index . . . . . . . . . . . . . . . . 43 4.6.6. quant_table_set_index . . . . . . . . . . . . . . . . 45
4.6.7. picture_structure . . . . . . . . . . . . . . . . . . 43 4.6.7. picture_structure . . . . . . . . . . . . . . . . . . 45
4.6.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 43 4.6.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 45
4.6.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 44 4.6.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 46
4.7. Slice Content . . . . . . . . . . . . . . . . . . . . . . 44 4.7. Slice Content . . . . . . . . . . . . . . . . . . . . . . 46
4.7.1. primary_color_count . . . . . . . . . . . . . . . . . 44 4.7.1. primary_color_count . . . . . . . . . . . . . . . . . 46
4.7.2. plane_pixel_height . . . . . . . . . . . . . . . . . 44 4.7.2. plane_pixel_height . . . . . . . . . . . . . . . . . 46
4.7.3. slice_pixel_height . . . . . . . . . . . . . . . . . 45 4.7.3. slice_pixel_height . . . . . . . . . . . . . . . . . 47
4.7.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 45 4.7.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 47
4.8. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.8. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.8.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 45 4.8.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 47
4.8.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 46 4.8.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 48
4.8.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 46 4.8.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 48
4.8.4. sample_difference . . . . . . . . . . . . . . . . . . 46 4.8.4. sample_difference . . . . . . . . . . . . . . . . . . 48
4.9. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 46 4.9. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 48
4.9.1. slice_size . . . . . . . . . . . . . . . . . . . . . 47 4.9.1. slice_size . . . . . . . . . . . . . . . . . . . . . 49
4.9.2. error_status . . . . . . . . . . . . . . . . . . . . 47 4.9.2. error_status . . . . . . . . . . . . . . . . . . . . 49
4.9.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 47 4.9.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 49
5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 47 5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 49
6. Security Considerations . . . . . . . . . . . . . . . . . . . 48 6. Security Considerations . . . . . . . . . . . . . . . . . . . 50
7. Media Type Definition . . . . . . . . . . . . . . . . . . . . 49 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 51
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50 7.1. Media Type Definition . . . . . . . . . . . . . . . . . . 51
9. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 50 8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 52
10. Normative References . . . . . . . . . . . . . . . . . . . . 50 9. Normative References . . . . . . . . . . . . . . . . . . . . 52
11. Informative References . . . . . . . . . . . . . . . . . . . 51 10. Informative References . . . . . . . . . . . . . . . . . . . 53
Appendix A. Multi-theaded decoder implementation suggestions . . 53 Appendix A. Multi-theaded decoder implementation suggestions . . 55
Appendix B. Future handling of some streams created by non Appendix B. Future handling of some streams created by non
conforming encoders . . . . . . . . . . . . . . . . . . . 53 conforming encoders . . . . . . . . . . . . . . . . . . . 55
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 55
1. Introduction 1. Introduction
This document describes FFV1, a lossless video encoding format. The This document describes FFV1, a lossless video encoding format. The
design of FFV1 considers the storage of image characteristics, data design of FFV1 considers the storage of image characteristics, data
fixity, and the optimized use of encoding time and storage fixity, and the optimized use of encoding time and storage
requirements. FFV1 is designed to support a wide range of lossless requirements. FFV1 is designed to support a wide range of lossless
video applications such as long-term audiovisual preservation, video applications such as long-term audiovisual preservation,
scientific imaging, screen recording, and other video encoding scientific imaging, screen recording, and other video encoding
scenarios that seek to avoid the generational loss of lossy video scenarios that seek to avoid the generational loss of lossy video
encodings. encodings.
This document defines version 0, 1 and 3 of FFV1. The distinctions This document defines version 0, 1 and 3 of FFV1. The distinctions
of the versions are provided throughout the document, but in summary: of the versions are provided throughout the document, but in summary:
* Version 0 of FFV1 was the original implementation of FFV1 and has * Version 0 of FFV1 was the original implementation of FFV1 and has
been in non-experimental use since April 14, 2006 [FFV1_V0]. been flagged as stable on April 14, 2006 [FFV1_V0].
* Version 1 of FFV1 adds support of more video bit depths and has * Version 1 of FFV1 adds support of more video bit depths and has
been in use since April 24, 2009 [FFV1_V1]. been has been flagged as stable on April 24, 2009 [FFV1_V1].
* Version 2 of FFV1 only existed in experimental form and is not * Version 2 of FFV1 only existed in experimental form and is not
described by this document, but is available as a LyX file at described by this document, but is available as a LyX file at
https://github.com/FFmpeg/FFV1/ https://github.com/FFmpeg/FFV1/
blob/8ad772b6d61c3dd8b0171979a2cd9f11924d5532/ffv1.lyx blob/8ad772b6d61c3dd8b0171979a2cd9f11924d5532/ffv1.lyx
(https://github.com/FFmpeg/FFV1/ (https://github.com/FFmpeg/FFV1/
blob/8ad772b6d61c3dd8b0171979a2cd9f11924d5532/ffv1.lyx). blob/8ad772b6d61c3dd8b0171979a2cd9f11924d5532/ffv1.lyx).
* Version 3 of FFV1 adds several features such as increased * Version 3 of FFV1 adds several features such as increased
description of the characteristics of the encoding images and description of the characteristics of the encoding images and
embedded CRC data to support fixity verification of the encoding. embedded CRC data to support fixity verification of the encoding.
Version 3 has been in non-experimental use since August 17, 2013 Version 3 has been flagged as stable on August 17, 2013 [FFV1_V3].
[FFV1_V3].
This document assumes familiarity with mathematical and coding This document assumes familiarity with mathematical and coding
concepts such as Range coding [range-coding] and YCbCr color spaces concepts such as Range coding [range-coding] and YCbCr color spaces
[YCbCr]. [YCbCr].
This specification describes the valid bitstream and how to decode This specification describes the valid bitstream and how to decode
such valid bitstream. Bitstreams not conforming to this such valid bitstream. Bitstreams not conforming to this
specification or how they are handled is outside this specification. specification or how they are handled is outside this specification.
A decoder could reject every invalid bitstream or attempt to perform A decoder could reject every invalid bitstream or attempt to perform
error concealment or re-download or use a redundant copy of the error concealment or re-download or use a redundant copy of the
skipping to change at page 5, line 15 skipping to change at page 5, line 15
2. Notation and Conventions 2. Notation and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2.1. Definitions 2.1. Definitions
"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. (when required) a "Configuration Record" into a bitstream.
"Sample": The smallest addressable representation of a color "Sample": The smallest addressable representation of a color
component 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), Luma (Y), Blue-difference Chroma (Cb), Red-difference Chroma (Cr),
Transparency, Red, Green, and Blue. Transparency, Red, Green, and Blue.
"Plane": A discrete component of a static image comprised of "Symbol": A value stored in the bitstream, which is defined and
"Samples" that represent a specific quantification of "Samples" of decoded through one of the methods described in Table 4.
that image.
"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 "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 too large for normal storage and that an alternate storage method is
used. used.
"MSB": Most Significant Bit, the bit that can cause the largest "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 "VLC": Variable Length Code, a code that maps source symbols to a
variable number of bits. variable number of bits.
"RGB": A reference to the method of storing the value of a "Pixel" by "RGB": A reference to the method of storing the value of a Pixel by
using three numeric values that represent Red, Green, and Blue. using three numeric values that represent Red, Green, and Blue.
"YCbCr": A reference to the method of storing the value of a "Pixel" "YCbCr": A reference to the method of storing the value of a Pixel by
by using three numeric values that represent the luma of the "Pixel" using three numeric values that represent the luma of the Pixel (Y)
(Y) and the chroma of the "Pixel" (Cb and Cr). YCbCr word is used and the chroma of the Pixel (Cb and Cr). YCbCr word is used for
for historical reasons and currently references any color space historical reasons and currently references any color space relying
relying on 1 luma "Sample" and 2 chroma "Samples", e.g. YCbCr, YCgCo on 1 luma Sample and 2 chroma Samples, e.g. YCbCr, YCgCo or ICtCp.
or ICtCp. The exact meaning of the three numeric values is The exact meaning of the three numeric values is unspecified.
unspecified.
2.2. Conventions 2.2. Conventions
2.2.1. Pseudo-code 2.2.1. Pseudo-code
The FFV1 bitstream is described in this document using 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 Note that the pseudo-code is used for clarity in order to illustrate
the structure of FFV1 and not intended to specify any particular the structure of FFV1 and not intended to specify any particular
implementation. The pseudo-code used is based upon the C programming 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. keywords as well as functions defined within this document.
In some instances, pseudo-code is presented in a two-column format 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 such as shown in Figure 1. In this form the "type" column provides a
symbol as defined in Table 4 that defines the storage of the data Symbol as defined in Table 4 that defines the storage of the data
referenced in that same line of pseudo-code. referenced in that same line of pseudo-code.
pseudo-code | type pseudo-code | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
ExamplePseudoCode( ) { | ExamplePseudoCode( ) { |
value | ur value | ur
} | } |
Figure 1: A depiction of type-labelled pseudo-code used within Figure 1: A depiction of type-labelled pseudo-code used within
this document. this document.
skipping to change at page 7, line 28 skipping to change at page 7, line 34
"a--" is equivalent to a is assigned a - 1. "a--" is equivalent to a is assigned a - 1.
"a += b" is equivalent to a is assigned a + b. "a += b" is equivalent to a is assigned a + b.
"a -= b" is equivalent to a is assigned a - b. "a -= b" is equivalent to a is assigned a - b.
"a *= b" is equivalent to a is assigned a * b. "a *= b" is equivalent to a is assigned a * b.
2.2.4. Comparison Operators 2.2.4. Comparison Operators
"a > b" 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. "a ? b : c" if a is true, then b, otherwise c.
2.2.5. Mathematical Functions 2.2.5. Mathematical Functions
"floor(a)" means the largest integer less than or equal to a. "floor(a)" means the largest integer less than or equal to a.
"ceil(a)" means the smallest integer greater than or equal to a. "ceil(a)" means the smallest integer greater than or equal to a.
"sign(a)" extracts the sign of a number, i.e. if a < 0 then -1, else "sign(a)" extracts the sign of a number, i.e. if a < 0 then -1, else
if a > 0 then 1, else 0. if a > 0 then 1, else 0.
"abs(a)" means the absolute value of a, i.e. "abs(a)" = "sign(a) * "abs(a)" means the absolute value of a, i.e. "abs(a)" = "sign(a) *
a". a".
"log2(a)" means the base-two logarithm of a. "log2(a)" means the base-two logarithm of a.
"min(a,b)" means the 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, "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). 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 B implies A.
"A <==> B" means A <== B , B <== A. "A <==> B" means A <== B , B <== A.
a_(b) means the b-th value of a sequence of a a_(b) means the b-th value of a sequence of a
skipping to change at page 8, line 39 skipping to change at page 9, line 8
When order of precedence is not indicated explicitly by use of When order of precedence is not indicated explicitly by use of
parentheses, operations are evaluated in the following order (from parentheses, operations are evaluated in the following order (from
top to bottom, operations of same precedence being evaluated from top to bottom, operations of same precedence being evaluated from
left to right). This order of operations is based on the order of left to right). This order of operations is based on the order of
operations used in Standard C. operations used in Standard C.
a++, a-- a++, a--
!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, 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 : c
a = b, a += b, a -= b, a *= b a = b, a += b, a -= b, a *= b
2.2.7. Range 2.2.7. Range
"a...b" means any value starting from a to b, inclusive. "a...b" means any value from a to b, inclusive.
2.2.8. NumBytes 2.2.8. NumBytes
"NumBytes" is a non-negative integer that expresses the size in 8-bit "NumBytes" is a non-negative integer that expresses the size in 8-bit
octets of a particular FFV1 "Configuration Record" or "Frame". FFV1 octets of a particular FFV1 "Configuration Record" or "Frame". FFV1
relies on its "Container" to store the "NumBytes" values; see relies on its Container to store the "NumBytes" values; see
Section 4.3.3. Section 4.3.3.
2.2.9. Bitstream Functions 2.2.9. Bitstream Functions
2.2.9.1. remaining_bits_in_bitstream 2.2.9.1. remaining_bits_in_bitstream
"remaining_bits_in_bitstream( )" means the count of remaining bits "remaining_bits_in_bitstream( NumBytes )" means the count of
after the pointer in that "Configuration Record" or "Frame". It is remaining bits after the pointer in that "Configuration Record" or
computed from the "NumBytes" value multiplied by 8 minus the count of "Frame". It is computed from the "NumBytes" value multiplied by 8
bits of that "Configuration Record" or "Frame" already read by the minus the count of bits of that "Configuration Record" or "Frame"
bitstream parser. already read by the bitstream parser.
2.2.9.2. remaining_symbols_in_syntax 2.2.9.2. remaining_symbols_in_syntax
"remaining_symbols_in_syntax( )" is true as long as the RangeCoder "remaining_symbols_in_syntax( )" is true as long as the RangeCoder
has not consumed all the given input bytes. has not consumed all the given input bytes.
2.2.9.3. byte_aligned 2.2.9.3. byte_aligned
"byte_aligned( )" is true if "remaining_bits_in_bitstream( NumBytes "byte_aligned( )" is true if "remaining_bits_in_bitstream( NumBytes
)" is a multiple of 8, otherwise false. )" is a multiple of 8, otherwise false.
2.2.9.4. get_bits 2.2.9.4. get_bits
"get_bits( i )" is the action to read the next "i" bits in the "get_bits( i )" is the action to read the next "i" bits in the
bitstream, from most significant bit to least significant bit, and to bitstream, from most significant bit to least significant bit, and to
return the corresponding value. The pointer is increased by "i". return the corresponding value. The pointer is increased by "i".
3. Sample Coding 3. Sample Coding
For each "Slice" (as described in Section 4.5) of a "Frame", the For each "Slice" (as described in Section 4.5) of a Frame, the
"Planes", "Lines", and "Samples" are coded in an order determined by Planes, Lines, and Samples are coded in an order determined by the
the "Color Space" (see Section 3.7). Each "Sample" is predicted by color space (see Section 3.7). Each Sample is predicted by the
the median predictor as described in Section 3.3 from other "Samples" median predictor as described in Section 3.3 from other Samples
within the same "Plane" and the difference is stored using the method within the same Plane and the difference is stored using the method
described in Section 3.8. described in Section 3.8.
3.1. Border 3.1. Border
A border is assumed for each coded "Slice" for the purpose of the A border is assumed for each coded "Slice" for the purpose of the
median predictor and context according to the following rules: median predictor and context according to the following rules:
* one column of "Samples" to the left of the coded slice is assumed * one column of Samples to the left of the coded slice is assumed as
as identical to the "Samples" of the leftmost column of the coded identical to the Samples of the leftmost column of the coded slice
slice shifted down by one row. The value of the topmost "Sample" shifted down by one row. The value of the topmost Sample of the
of the column of "Samples" to the left of the coded slice is column of Samples to the left of the coded slice is assumed to be
assumed to be "0" "0"
* one column of "Samples" to the right of the coded slice is assumed * one column of Samples to the right of the coded slice is assumed
as identical to the "Samples" of the rightmost column of the coded as identical to the Samples of the rightmost column of the coded
slice slice
* an additional column of "Samples" to the left of the coded slice * an additional column of Samples to the left of the coded slice and
and two rows of "Samples" above the coded slice are assumed to be two rows of Samples above the coded slice are assumed to be "0"
"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. arrangement along with its assumed border.
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | 0 | | 0 | 0 | 0 | | 0 | | 0 | 0 | | 0 | 0 | 0 | | 0 |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | 0 | | 0 | 0 | 0 | | 0 | | 0 | 0 | | 0 | 0 | 0 | | 0 |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | 0 | | a | b | c | | c | | 0 | 0 | | a | b | c | | c |
skipping to change at page 10, line 46 skipping to change at page 11, line 24
| 0 | a | | d | e | f | | f | | 0 | a | | d | e | f | | f |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
| 0 | d | | g | h | i | | i | | 0 | d | | g | h | i | | i |
+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+
Figure 2: A depiction of FFV1's assumed border for a set example Figure 2: A depiction of FFV1's assumed border for a set example
Samples. Samples.
3.2. Samples 3.2. Samples
Relative to any "Sample" "X", six other relatively positioned Relative to any Sample "X", six other relatively positioned Samples
"Samples" from the coded "Samples" and presumed border are identified from the coded Samples and presumed border are identified according
according to the labels used in Figure 3. The labels for these to the labels used in Figure 3. The labels for these relatively
relatively positioned "Samples" are used within the median predictor positioned Samples are used within the median predictor and context.
and context.
+---+---+---+---+ +---+---+---+---+
| | | T | | | | | T | |
+---+---+---+---+ +---+---+---+---+
| |tl | t |tr | | |tl | t |tr |
+---+---+---+---+ +---+---+---+---+
| L | l | X | | | L | l | X | |
+---+---+---+---+ +---+---+---+---+
Figure 3: A depiction of how relatively positions Samples are Figure 3: A depiction of how relatively positioned Samples are
references within this document. referenced within this document.
The labels for these relative "Samples" are made of the first letters The labels for these relative Samples are made of the first letters
of the words Top, Left and Right. of the words Top, Left and Right.
3.3. Median Predictor 3.3. Median Predictor
The prediction for any "Sample" value at position "X" may be computed The prediction for any Sample value at position "X" may be computed
based upon the relative neighboring values of "l", "t", and "tl" via based upon the relative neighboring values of "l", "t", and "tl" via
this equation: this equation:
median(l, t, l + t - tl) median(l, t, l + t - tl)
Note, this prediction template is also used in [ISO.14495-1.1999] and Note, this prediction template is also used in [ISO.14495-1.1999] and
[HuffYUV]. [HuffYUV].
Exception for the median predictor: if "colorspace_type == 0 && Exception for the median predictor: if "colorspace_type == 0 &&
bits_per_raw_sample == 16 && ( coder_type == 1 || coder_type == 2 )", bits_per_raw_sample == 16 && ( coder_type == 1 || coder_type == 2 )"
the following median predictor MUST be used: (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) median(left16s, top16s, left16s + top16s - diag16s)
where: where:
left16s = l >= 32768 ? ( l - 65536 ) : l left16s = l >= 32768 ? ( l - 65536 ) : l
top16s = t >= 32768 ? ( t - 65536 ) : t top16s = t >= 32768 ? ( t - 65536 ) : t
diag16s = tl >= 32768 ? ( tl - 65536 ) : tl diag16s = tl >= 32768 ? ( tl - 65536 ) : tl
Background: a two's complement signed 16-bit signed integer was used Background: a two's complement 16-bit signed integer was used for
for storing "Sample" values in all known implementations of FFV1 storing Sample values in all known implementations of FFV1 bitstream.
bitstream. So in some circumstances, the most significant bit was So in some circumstances, the most significant bit was wrongly
wrongly interpreted (used as a sign bit instead of the 16th bit of an interpreted (used as a sign bit instead of the 16th bit of an
unsigned integer). Note that when the issue was discovered, the only unsigned integer). Note that when the issue was discovered, the only
configuration of all known implementations being impacted is 16-bit configuration of all known implementations being impacted is 16-bit
YCbCr with no Pixel transformation with Range Coder coder, as other YCbCr with no Pixel transformation with Range Coder coder, as other
potentially impacted configurations (e.g. 15/16-bit JPEG2000-RCT with potentially impacted configurations (e.g. 15/16-bit JPEG2000-RCT with
Range Coder coder, or 16-bit content with Golomb Rice coder) were Range Coder coder, or 16-bit content with Golomb Rice coder) were
implemented nowhere [ISO.15444-1.2016]. In the meanwhile, 16-bit implemented nowhere [ISO.15444-1.2016]. In the meanwhile, 16-bit
JPEG2000-RCT with Range Coder coder was implemented without this JPEG2000-RCT with Range Coder coder was implemented without this
issue in one implementation and validated by one conformance checker. issue in one implementation and validated by one conformance checker.
It is expected (to be confirmed) to remove this exception for the It is expected (to be confirmed) to remove this exception for the
median predictor in the next version of the FFV1 bitstream. median predictor in the next version of the FFV1 bitstream.
skipping to change at page 12, line 28 skipping to change at page 13, line 7
Q_(j)[k] = quant_tables[i][j][k&255] Q_(j)[k] = quant_tables[i][j][k&255]
Figure 4 Figure 4
In this formula, "i" is the Quantization Table Set index, "j" is the In this formula, "i" is the Quantization Table Set index, "j" is the
Quantized Table index, "k" the Quantized Sample Difference. Quantized Table index, "k" the Quantized Sample Difference.
3.5. Context 3.5. Context
Relative to any "Sample" "X", the Quantized Sample Differences "L-l", Relative to any Sample "X", the Quantized Sample Differences "L-l",
"l-tl", "tl-t", "T-t", and "t-tr" are used as context: "l-tl", "tl-t", "T-t", and "t-tr" are used as context:
context = Q_(0)[l - tl] + context = Q_(0)[l - tl] +
Q_(1)[tl - t] + Q_(1)[tl - t] +
Q_(2)[t - tr] + Q_(2)[t - tr] +
Q_(3)[L - l] + Q_(3)[L - l] +
Q_(4)[T - t] Q_(4)[T - t]
Figure 5 Figure 5
If "context >= 0" then "context" is used and the difference between If "context >= 0" then "context" is used and the difference between
the "Sample" and its predicted value is encoded as is, else the Sample and its predicted value is encoded as is, else "-context"
"-context" is used and the difference between the "Sample" and its is used and the difference between the Sample and its predicted value
predicted value is encoded with a flipped sign. is encoded with a flipped sign.
3.6. Quantization Table Set Indexes 3.6. Quantization Table Set Indexes
For each "Plane" of each slice, a Quantization Table Set is selected For each Plane of each slice, a Quantization Table Set is selected
from an index: from an index:
* For Y "Plane", "quant_table_set_index[ 0 ]" index is used * For Y Plane, "quant_table_set_index[ 0 ]" index is used
* For Cb and Cr "Planes", "quant_table_set_index[ 1 ]" index is used * For Cb and Cr Planes, "quant_table_set_index[ 1 ]" index is used
* For extra "Plane", "quant_table_set_index[ (version <= 3 ||
* For extra Plane, "quant_table_set_index[ (version <= 3 ||
chroma_planes) ? 2 : 1 ]" index is used chroma_planes) ? 2 : 1 ]" index is used
Background: in first implementations of FFV1 bitstream, the index for Background: in first implementations of FFV1 bitstream, the index for
Cb and Cr "Planes" was stored even if it is not used (chroma_planes Cb and Cr Planes was stored even if it is not used (chroma_planes set
set to 0), this index is kept for "version" <= 3 in order to keep to 0), this index is kept for "version" <= 3 in order to keep
compatibility with FFV1 bitstreams in the wild. compatibility with FFV1 bitstreams in the wild.
3.7. Color spaces 3.7. Color spaces
FFV1 supports several color spaces. The count of allowed coded FFV1 supports several color spaces. The count of allowed coded
planes and the meaning of the extra "Plane" are determined by the planes and the meaning of the extra Plane are determined by the
selected color space. selected color space.
The FFV1 bitstream interleaves data in an order determined by the The FFV1 bitstream interleaves data in an order determined by the
color space. In YCbCr for each "Plane", each "Line" is coded from color space. In YCbCr for each Plane, each Line is coded from top to
top to bottom and for each "Line", each "Sample" is coded from left bottom and for each Line, each Sample is coded from left to right.
to right. In JPEG2000-RCT for each "Line" from top to bottom, each In JPEG2000-RCT for each Line from top to bottom, each Plane is coded
"Plane" is coded and for each "Plane", each "Sample" is encoded from and for each Plane, each Sample is encoded from left to right.
left to right.
3.7.1. YCbCr 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 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 together. Omitting the Cb and Cr Planes codes the frames in
grayscale without color data. grayscale without color data.
An optional transparency "Plane" can be used to code transparency An optional transparency Plane can be used to code transparency data.
data.
An FFV1 "Frame" using YCbCr MUST use one of the following An FFV1 Frame using YCbCr MUST use one of the following arrangements:
arrangements:
* Y * Y
* Y, Transparency * Y, Transparency
* Y, Cb, Cr * Y, Cb, Cr
* Y, Cb, Cr, Transparency * Y, Cb, Cr, Transparency
The Y "Plane" MUST be coded first. If the Cb and Cr "Planes" are The Y Plane MUST be coded first. If the Cb and Cr Planes are used
used then they MUST be coded after the Y "Plane". If a transparency then they MUST be coded after the Y Plane. If a transparency Plane
"Plane" is used, then it MUST be coded last. is used, then it MUST be coded last.
3.7.2. RGB 3.7.2. RGB
This color space allows 3 or 4 "Planes". This color space allows 3 or 4 Planes.
An optional transparency "Plane" can be used to code transparency An optional transparency Plane can be used to code transparency data.
data.
JPEG2000-RCT is a Reversible Color Transform that codes RGB (red, 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 [ISO.15444-1.2016]. Reversible Pixel transformations between YCbCr
and RGB use the following formulae. and RGB use the following formulae.
Cb = b - g Cb = b - g
Cr = r - g Cr = r - g
Y = g + (Cb + Cr) >> 2 Y = g + (Cb + Cr) >> 2
g = Y - (Cb + Cr) >> 2 g = Y - (Cb + Cr) >> 2
r = Cr + g r = Cr + g
b = Cb + g b = Cb + g
skipping to change at page 14, line 42 skipping to change at page 15, line 16
Cr = r - b Cr = r - b
Y = b +(Cb + Cr) >> 2 Y = b +(Cb + Cr) >> 2
b = Y -(Cb + Cr) >> 2 b = Y -(Cb + Cr) >> 2
r = Cr + b r = Cr + b
g = Cb + b g = Cb + b
Figure 7 Figure 7
Background: At the time of this writing, in all known implementations Background: At the time of this writing, in all known implementations
of FFV1 bitstream, when "bits_per_raw_sample" was between 9 and 15 of FFV1 bitstream, when "bits_per_raw_sample" was between 9 and 15
inclusive and "extra_plane" is 0, GBR "Planes" were used as BGR inclusive and "extra_plane" is 0, GBR Planes were used as BGR Planes
"Planes" during both encoding and decoding. In the meanwhile, 16-bit during both encoding and decoding. In the meanwhile, 16-bit
JPEG2000-RCT was implemented without this issue in one implementation JPEG2000-RCT was implemented without this issue in one implementation
and validated by one conformance checker. Methods to address this and validated by one conformance checker. Methods to address this
exception for the transform are under consideration for the next exception for the transform are under consideration for the next
version of the FFV1 bitstream. version of the FFV1 bitstream.
Cb and Cr are positively offset by "1 << bits_per_raw_sample" after Cb and Cr are positively offset by "1 << bits_per_raw_sample" after
the conversion from RGB to the modified YCbCr and are negatively the conversion from RGB to the modified YCbCr and are negatively
offseted by the same value before the conversion from the modified offseted by the same value before the conversion from the modified
YCbCr to RGB, in order to have only non-negative values after the YCbCr to RGB, in order to have only non-negative values after the
conversion. conversion.
When FFV1 uses the JPEG2000-RCT, the horizontal "Lines" are When FFV1 uses the JPEG2000-RCT, the horizontal Lines are interleaved
interleaved to improve caching efficiency since it is most likely to improve caching efficiency since it is most likely that the
that the JPEG2000-RCT will immediately be converted to RGB during JPEG2000-RCT will immediately be converted to RGB during decoding.
decoding. The interleaved coding order is also Y, then Cb, then Cr, The interleaved coding order is also Y, then Cb, then Cr, and then,
and then if used transparency. if used, transparency.
As an example, a "Frame" that is two "Pixels" wide and two "Pixels" As an example, a Frame that is two Pixels wide and two Pixels high,
high, could comprise the following structure: could comprise the following structure:
+------------------------+------------------------+ +------------------------+------------------------+
| Pixel(1,1) | Pixel(2,1) | | Pixel(1,1) | Pixel(2,1) |
| Y(1,1) Cb(1,1) Cr(1,1) | Y(2,1) Cb(2,1) Cr(2,1) | | Y(1,1) Cb(1,1) Cr(1,1) | Y(2,1) Cb(2,1) Cr(2,1) |
+------------------------+------------------------+ +------------------------+------------------------+
| Pixel(1,2) | Pixel(2,2) | | Pixel(1,2) | Pixel(2,2) |
| Y(1,2) Cb(1,2) Cr(1,2) | Y(2,2) Cb(2,2) Cr(2,2) | | Y(1,2) Cb(1,2) Cr(1,2) | Y(2,2) Cb(2,2) Cr(2,2) |
+------------------------+------------------------+ +------------------------+------------------------+
In JPEG2000-RCT, the coding order would be left to right and then top In JPEG2000-RCT, the coding order would be left to right and then top
to bottom, with values interleaved by "Lines" and stored in this to bottom, with values interleaved by Lines and stored in this order:
order:
Y(1,1) Y(2,1) Cb(1,1) Cb(2,1) Cr(1,1) Cr(2,1) Y(1,2) Y(2,2) Cb(1,2) Y(1,1) Y(2,1) Cb(1,1) Cb(2,1) Cr(1,1) Cr(2,1) Y(1,2) Y(2,2) Cb(1,2)
Cb(2,2) Cr(1,2) Cr(2,2) Cb(2,2) Cr(1,2) Cr(2,2)
3.8. Coding of the Sample Difference 3.8. Coding of the Sample Difference
Instead of coding the n+1 bits of the Sample Difference with Huffman Instead of coding the n+1 bits of the Sample Difference with Huffman
or Range coding (or n+2 bits, in the case of JPEG2000-RCT), only the or Range coding (or n+2 bits, in the case of JPEG2000-RCT), only the
n (or n+1, in the case of JPEG2000-RCT) least significant bits are n (or n+1, in the case of 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 + the equation below, the term "bits" represents "bits_per_raw_sample +
1" for JPEG2000-RCT or "bits_per_raw_sample" otherwise: 1" for JPEG2000-RCT or "bits_per_raw_sample" otherwise:
coder_input = [(sample_difference + 2 ^ (bits - 1)) & coder_input = [(sample_difference + 2 ^ (bits - 1)) &
(2 ^ bits - 1)] - 2 ^ (bits - 1) (2 ^ bits - 1)] - 2 ^ (bits - 1)
Figure 8: Description of the coding of the Sample Difference in Figure 8: Description of the coding of the Sample Difference in
the bitstream. the bitstream.
3.8.1. Range Coding Mode 3.8.1. Range Coding Mode
Early experimental versions of FFV1 used the CABAC Arithmetic coder Early experimental versions of FFV1 used the CABAC Arithmetic coder
from H.264 as defined in [ISO.14496-10.2014] but due to the uncertain from H.264 as defined in [ISO.14496-10.2014] but due to the uncertain
patent/royalty situation, as well as its slightly worse performance, patent/royalty situation, as well as its slightly worse performance,
CABAC was replaced by a Range coder based on an algorithm defined by 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 3.8.1.1. Range Binary Values
To encode binary digits efficiently a Range coder is used. C_(i) is 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 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 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 state. The length of the bytestream encoding n binary symbols is
j_(n) bytes. j_(n) bytes.
r_(i) = floor( ( R_(i) * S_(i, C_(i)) ) / 2 ^ 8 ) 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 S_(i + 1, C_(i)) = zero_state_(S_(i, C_(i))) AND
l_(i) = L_(i) AND l_(i) = L_(i) AND
t_(i) = R_(i) - r_(i) <== t_(i) = R_(i) - r_(i) <==
b_(i) = 0 <==> b_(i) = 0 <==>
L_(i) < R_(i) - r_(i) L_(i) < R_(i) - r_(i)
S_(i + 1, C_(i)) = one_state_(S_(i, C_(i))) AND S_(i + 1, C_(i)) = one_state_(S_(i, C_(i))) AND
l_(i) = L_(i) - R_(i) + r_(i) AND l_(i) = L_(i) - R_(i) + r_(i) AND
t_(i) = r_(i) <== t_(i) = r_(i) <==
skipping to change at page 17, line 18 skipping to change at page 17, line 34
Figure 13 Figure 13
L_(0) = 2 ^ 8 * B_(0) + B_(1) L_(0) = 2 ^ 8 * B_(0) + B_(1)
Figure 14 Figure 14
j_(0) = 2 j_(0) = 2
Figure 15 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 3.8.1.1.1. Termination
The range coder can be used in three modes. The range coder can be used in three modes.
* In "Open mode" when decoding, every symbol the reader attempts to * In "Open mode" when decoding, every Symbol the reader attempts to
read is available. In this mode arbitrary data can have been read is available. In this mode arbitrary data can have been
appended without affecting the range coder output. This mode is appended without affecting the range coder output. This mode is
not used in FFV1. not used in FFV1.
* In "Closed mode" the length in bytes of the bytestream is provided * In "Closed mode" the length in bytes of the bytestream is provided
to the range decoder. Bytes beyond the length are read as 0 by to the range decoder. Bytes beyond the length are read as 0 by
the range decoder. This is generally one byte shorter than the the range decoder. This is generally one byte shorter than the
open mode. open mode.
* In "Sentinel mode" the exact length in bytes is not known and thus * In "Sentinel mode" the exact length in bytes is not known and thus
the range decoder MAY read into the data that follows the range the range decoder MAY read into the data that follows the range
coded bytestream by one byte. In "Sentinel mode", the end of the coded bytestream by one byte. In "Sentinel mode", the end of the
range coded bytestream is a binary symbol with state 129, which range coded bytestream is a binary Symbol with state 129, which
value SHALL be discarded. After reading this symbol, the range value SHALL be discarded. After reading this Symbol, the range
decoder will have read one byte beyond the end of the range coded decoder will have read one byte beyond the end of the range coded
bytestream. This way the byte position of the end can be bytestream. This way the byte position of the end can be
determined. Bytestreams written in "Sentinel mode" can be read in determined. Bytestreams written in "Sentinel mode" can be read in
"Closed mode" if the length can be determined, in this case the "Closed mode" if the length can be determined, in this case the
last (sentinel) symbol will be read non-corrupted and be of value last (sentinel) Symbol will be read non-corrupted and be of value
0. 0.
Above describes the range decoding. Encoding is defined as any Above describes the range decoding. Encoding is defined as any
process which produces a decodable bytestream. process which produces a decodable bytestream.
There are three places where range coder termination is needed in There are three places where range coder termination is needed in
FFV1. First is in the "Configuration Record", in this case the size FFV1. First is in the "Configuration Record", in this case the size
of the range coded bytestream is known and handled as "Closed mode". 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 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 Golomb coded slices as "Sentinel mode". Third is the end of range
coded Slices which need to terminate before the CRC at their end. 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 This can be handled as "Sentinel mode" or as "Closed mode" if the CRC
position has been determined. position has been determined.
3.8.1.2. Range Non Binary Values 3.8.1.2. Range Non Binary Values
To encode scalar integers, it would be possible to encode each bit To encode scalar integers, it would be possible to encode each bit
separately and use the past bits as context. However that would mean separately and use the past bits as context. However that would 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 also requires more past data to reach a reasonably good estimate of
the probabilities. Alternatively assuming a Laplacian distribution the probabilities. Alternatively assuming a Laplacian distribution
and only dealing with its variance and mean (as in Huffman coding) and only dealing with its variance and mean (as in Huffman coding)
would also be possible, however, for maximum flexibility and 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, number is 0, and if not, encodes the number using its exponent,
mantissa and sign. The exact contexts used are best described by 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) { int get_symbol(RangeCoder *c, uint8_t *state, int is_signed) {
if (get_rac(c, state + 0) { if (get_rac(c, state + 0) {
return 0; return 0;
} }
int e = 0; int e = 0;
while (get_rac(c, state + 1 + min(e, 9)) { //1..10 while (get_rac(c, state + 1 + min(e, 9)) { //1..10
e++; e++;
} }
skipping to change at page 18, line 48 skipping to change at page 20, line 31
return a; return a;
} }
if (get_rac(c, state + 11 + min(e, 10))) { //11..21 if (get_rac(c, state + 11 + min(e, 10))) { //11..21
return -a; return -a;
} else { } else {
return a; return a;
} }
} }
Figure 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. Binary Values.
"get_symbol" is used for the read out of "sample_difference" "get_symbol" is used for the read out of "sample_difference"
indicated in Figure 8. indicated in Figure 8.
"get_rac" returns a boolean, computed from the bytestream as "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 3.8.1.3. Initial Values for the Context Model
At keyframes all Range coder state variables are set to their initial When "keyframe" (see Section 4.4) value is 1, all Range coder state
state. variables are set to their initial state.
3.8.1.4. State Transition Table 3.8.1.4. State Transition Table
one_state_(i) = one_state_(i) =
default_state_transition_(i) + state_transition_delta_(i) default_state_transition_(i) + state_transition_delta_(i)
Figure 17 Figure 20
zero_state_(i) = 256 - one_state_(256-i) zero_state_(i) = 256 - one_state_(256-i)
Figure 21
Figure 18
3.8.1.5. default_state_transition 3.8.1.5. default_state_transition
0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27, 0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27,
28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42,
43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57,
58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73,
74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88,
skipping to change at page 20, line 43 skipping to change at page 21, line 47
241,242,243,244,245,246,247,248,248, 0, 0, 0, 0, 0, 0, 0, 241,242,243,244,245,246,247,248,248, 0, 0, 0, 0, 0, 0, 0,
3.8.1.6. Alternative State Transition Table 3.8.1.6. Alternative State Transition Table
The alternative state transition table has been built using iterative The alternative state transition table has been built using iterative
minimization of frame sizes and generally performs better than the minimization of frame sizes and generally performs better than the
default. To use it, the "coder_type" (see Section 4.2.3) MUST be set default. To use it, the "coder_type" (see Section 4.2.3) MUST be set
to 2 and the difference to the default MUST be stored in the to 2 and the difference to the default MUST be stored in the
"Parameters", see Section 4.2. The reference implementation of FFV1 "Parameters", see Section 4.2. 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. Range coding is used.
0, 10, 10, 10, 10, 16, 16, 16, 28, 16, 16, 29, 42, 49, 20, 49, 0, 10, 10, 10, 10, 16, 16, 16, 28, 16, 16, 29, 42, 49, 20, 49,
59, 25, 26, 26, 27, 31, 33, 33, 33, 34, 34, 37, 67, 38, 39, 39, 59, 25, 26, 26, 27, 31, 33, 33, 33, 34, 34, 37, 67, 38, 39, 39,
40, 40, 41, 79, 43, 44, 45, 45, 48, 48, 64, 50, 51, 52, 88, 52, 40, 40, 41, 79, 43, 44, 45, 45, 48, 48, 64, 50, 51, 52, 88, 52,
53, 74, 55, 57, 58, 58, 74, 60,101, 61, 62, 84, 66, 66, 68, 69, 53, 74, 55, 57, 58, 58, 74, 60,101, 61, 62, 84, 66, 66, 68, 69,
skipping to change at page 21, line 37 skipping to change at page 22, line 37
175,189,179,181,186,183,192,185,200,187,191,188,190,197,193,196, 175,189,179,181,186,183,192,185,200,187,191,188,190,197,193,196,
197,194,195,196,198,202,199,201,210,203,207,204,205,206,208,214, 197,194,195,196,198,202,199,201,210,203,207,204,205,206,208,214,
209,211,221,212,213,215,224,216,217,218,219,220,222,228,223,225, 209,211,221,212,213,215,224,216,217,218,219,220,222,228,223,225,
226,224,227,229,240,230,231,232,233,234,235,236,238,239,237,242, 226,224,227,229,240,230,231,232,233,234,235,236,238,239,237,242,
241,243,242,244,245,246,247,248,249,250,251,252,252,253,254,255, 241,243,242,244,245,246,247,248,249,250,251,252,252,253,254,255,
Figure 19: Alternative state transition table for Range coding. Figure 22: Alternative state transition table for Range coding.
3.8.2. Golomb Rice Mode 3.8.2. Golomb Rice Mode
The end of the bitstream of the "Frame" is filled with 0-bits until The end of the bitstream of the Frame is padded with 0-bits until the
that the bitstream contains a multiple of 8 bits. bitstream contains a multiple of 8 bits.
3.8.2.1. Signed Golomb Rice Codes 3.8.2.1. Signed Golomb Rice Codes
This coding mode uses Golomb Rice codes. The VLC is split into two This coding mode uses Golomb Rice codes. The VLC is split into two
parts. The prefix stores the most significant bits and the suffix parts. The prefix stores the most significant bits and the suffix
stores the k least significant bits or stores the whole number in the stores the k least significant bits or stores the whole number in the
ESC case. ESC case.
int get_ur_golomb(k) { int get_ur_golomb(k) {
for (prefix = 0; prefix < 12; prefix++) { for (prefix = 0; prefix < 12; prefix++) {
if (get_bits(1)) { if (get_bits(1)) {
return get_bits(k) + (prefix << k); return get_bits(k) + (prefix << k);
} }
} }
return get_bits(bits) + 11; return get_bits(bits) + 11;
} }
Figure 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. integer in Golomb Rice mode.
int get_sr_golomb(k) { int get_sr_golomb(k) {
v = get_ur_golomb(k); v = get_ur_golomb(k);
if (v & 1) return - (v >> 1) - 1; if (v & 1) return - (v >> 1) - 1;
else return (v >> 1); else return (v >> 1);
} }
Figure 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. integer in Golomb Rice mode.
3.8.2.1.1. Prefix 3.8.2.1.1. Prefix
+================+=======+ +================+=======+
| bits | value | | bits | value |
+================+=======+ +================+=======+
| 1 | 0 | | 1 | 0 |
+----------------+-------+ +----------------+-------+
| 01 | 1 | | 01 | 1 |
skipping to change at page 23, line 16 skipping to change at page 24, line 16
+=========+========================================+ +=========+========================================+
+=========+========================================+ +=========+========================================+
| non ESC | the k least significant bits MSB first | | non ESC | the k least significant bits MSB first |
+---------+----------------------------------------+ +---------+----------------------------------------+
| ESC | the value - 11, in MSB first order | | ESC | the value - 11, in MSB first order |
+---------+----------------------------------------+ +---------+----------------------------------------+
Table 2 Table 2
"ESC" MUST NOT be used if the value can be coded as "non ESC". ESC MUST NOT be used if the value can be coded as non ESC.
3.8.2.1.3. Examples 3.8.2.1.3. Examples
Table 3 shows practical examples of how Signed Golomb Rice Codes are
decoded based on the series of bits extracted from the bitstream as
described by the method above:
+=====+=======================+=======+ +=====+=======================+=======+
| k | bits | value | | k | bits | value |
+=====+=======================+=======+ +=====+=======================+=======+
| 0 | 1 | 0 | | 0 | 1 | 0 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| 0 | 001 | 2 | | 0 | 001 | 2 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| 2 | 1 00 | 0 | | 2 | 1 00 | 0 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| 2 | 1 10 | 2 | | 2 | 1 10 | 2 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| 2 | 01 01 | 5 | | 2 | 01 01 | 5 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
| any | 000000000000 10000000 | 139 | | any | 000000000000 10000000 | 139 |
+-----+-----------------------+-------+ +-----+-----------------------+-------+
Table 3 Table 3: Examples of decoded Signed
Golomb Rice Codes.
3.8.2.2. Run Mode 3.8.2.2. Run Mode
Run mode is entered when the context is 0 and left as soon as a non-0 Run mode is entered when the context is 0 and left as soon as a non-0
difference is found. The level is identical to the predicted one. difference is found. The sample difference is identical to the
The run and the first different level are coded. 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 3.8.2.2.1. Run Length Coding
The run value is encoded in two parts. The prefix part stores the The run value is encoded in two parts. The prefix part stores the
more significant part of the run as well as adjusting the "run_index" more significant part of the run as well as adjusting the "run_index"
that determines the number of bits in the less significant part of that determines the number of bits in the less significant part of
the run. The second part of the value stores the less significant the run. The second part of the value stores the less significant
part of the run as it is. The "run_index" is reset for each "Plane" part of the run as it is. The "run_index" is reset for each Plane
and slice to 0. and slice to 0.
log2_run[41] = { log2_run[41] = {
0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1,
2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 3, 3, 3, 3,
4, 4, 5, 5, 6, 6, 7, 7, 4, 4, 5, 5, 6, 6, 7, 7,
8, 9,10,11,12,13,14,15, 8, 9,10,11,12,13,14,15,
16,17,18,19,20,21,22,23, 16,17,18,19,20,21,22,23,
24, 24,
}; };
skipping to change at page 25, line 49 skipping to change at page 27, line 44
-state->count + 1); -state->count + 1);
} else if (state->drift > 0) { } else if (state->drift > 0) {
state->bias = min(state->bias + 1, 127); state->bias = min(state->bias + 1, 127);
state->drift = min(state->drift - state->count, 0); state->drift = min(state->drift - state->count, 0);
} }
return ret; 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 Level coding is identical to the normal difference coding with the
exception that the 0 value is removed as it cannot occur: exception that the 0 value is removed as it cannot occur:
diff = get_vlc_symbol(context_state); diff = get_vlc_symbol(context_state);
if (diff >= 0) { if (diff >= 0) {
diff++; diff++;
} }
Note, this is different from JPEG-LS, which doesn't use prediction in Note, 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 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. slightly improved the compression rate.
3.8.2.5. Initial Values for the VLC context state 3.8.2.5. Initial Values for the VLC context state
At keyframes all coder state variables are set to their initial When "keyframe" (see Section 4.4) value is 1, all coder state
state. variables are set to their initial state.
drift = 0; drift = 0;
error_sum = 4; error_sum = 4;
bias = 0; bias = 0;
count = 1; count = 1;
4. Bitstream 4. Bitstream
An FFV1 bitstream is composed of a series of one or more "Frames" and An FFV1 bitstream is composed of a series of one or more Frames and
(when required) a "Configuration Record". (when required) a "Configuration Record".
Within the following sub-sections, pseudo-code is used to explain the Within the following sub-sections, pseudo-code is used, as described
structure of each FFV1 bitstream component, as described in in Section 2.2.1, to explain the structure of each FFV1 bitstream
Section 2.2.1. Table 4 lists symbols used to annotate that pseudo- component. Table 4 lists symbols used to annotate that pseudo-code
code in order to define the storage of the data referenced in that in order to define the storage of the data referenced in that line of
line of pseudo-code. pseudo-code.
+========+==============================================+ +========+=================================================+
| Symbol | Definition | | Symbol | Definition |
+========+==============================================+ +========+=================================================+
| u(n) | unsigned big endian integer using n bits | | u(n) | unsigned big endian integer Symbol using n bits |
+--------+----------------------------------------------+ +--------+-------------------------------------------------+
| sg | Golomb Rice coded signed scalar symbol coded | | sg | Golomb Rice coded signed scalar Symbol coded |
| | with the method described in Section 3.8.2 | | | 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 | | | method described in Section 3.8.1.1 |
+--------+----------------------------------------------+ +--------+-------------------------------------------------+
| ur | Range coded unsigned scalar symbol coded | | ur | Range coded unsigned scalar Symbol coded with |
| | with the method described in Section 3.8.1.2 | | | the method described in Section 3.8.1.2 |
+--------+----------------------------------------------+ +--------+-------------------------------------------------+
| sr | Range coded signed scalar symbol coded with | | sr | Range coded signed scalar Symbol coded with the |
| | the method described in Section 3.8.1.2 | | | method described in Section 3.8.1.2 |
+--------+----------------------------------------------+ +--------+-------------------------------------------------+
| sd | Sample difference coded with the method | | sd | Sample difference Symbol coded with the method |
| | described in Section 3.8 | | | described in Section 3.8 |
+--------+----------------------------------------------+ +--------+-------------------------------------------------+
Table 4: Definition of pseudo-code symbols for this Table 4: Definition of pseudo-code symbols for this
document. document.
The following MUST be provided by external means during The following MUST be provided by external means during
initialization of the decoder: initialization of the decoder:
"frame_pixel_width" is defined as "Frame" width in "Pixels". "frame_pixel_width" is defined as Frame width in Pixels.
"frame_pixel_height" is defined as "Frame" height in "Pixels". "frame_pixel_height" is defined as Frame height in Pixels.
Default values at the decoder initialization phase: Default values at the decoder initialization phase:
"ConfigurationRecordIsPresent" is set to 0. "ConfigurationRecordIsPresent" is set to 0.
4.1. Quantization Table Set 4.1. Quantization Table Set
The Quantization Table Sets are stored by storing the number of equal The Quantization Table Sets are stored by storing the number of equal
entries -1 of the first half of the table (represented as "len - 1" entries -1 of the first half of the table (represented as "len - 1"
in the pseudo-code below) using the method described in in the pseudo-code below) using the method described in
skipping to change at page 29, line 14 skipping to change at page 31, line 14
4.1.2. context_count 4.1.2. context_count
"context_count[ i ]" indicates the count of contexts for Quantization "context_count[ i ]" indicates the count of contexts for Quantization
Table Set "i". "context_count[ i ]" MUST be less than or equal to Table Set "i". "context_count[ i ]" MUST be less than or equal to
32768. 32768.
4.2. Parameters 4.2. Parameters
The "Parameters" section contains significant characteristics about The "Parameters" section contains significant characteristics about
the 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), version 0 and 1) or the whole FFV1 bitstream (other versions),
including the stream version, color configuration, and quantization including the stream version, color configuration, and quantization
tables. Figure 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. "Parameters" has its own initial states, all set to 128.
pseudo-code | type pseudo-code | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Parameters( ) { | Parameters( ) { |
version | ur version | ur
if (version >= 3) { | if (version >= 3) { |
micro_version | ur micro_version | ur
} | } |
skipping to change at page 30, line 50 skipping to change at page 32, line 50
initial_state_delta[ i ][ j ][ k ] | sr initial_state_delta[ i ][ j ][ k ] | sr
} | } |
} | } |
} | } |
} | } |
ec | ur ec | ur
intra | ur intra | ur
} | } |
} | } |
Figure 22: A pseudo-code description of the bitstream contents. Figure 25: A pseudo-code description of the bitstream contents.
CONTEXT_SIZE is 32. CONTEXT_SIZE is 32.
4.2.1. version 4.2.1. version
"version" specifies the version of the FFV1 bitstream. "version" specifies the version of the FFV1 bitstream.
Each version is incompatible with other versions: decoders SHOULD Each version is incompatible with other versions: decoders SHOULD
reject FFV1 bitstreams due to an unknown version. reject FFV1 bitstreams due to an unknown version.
skipping to change at page 33, line 15 skipping to change at page 35, line 15
If "state_transition_delta" is not present in the FFV1 bitstream, all If "state_transition_delta" is not present in the FFV1 bitstream, all
Range coder custom state transition table elements are assumed to be Range coder custom state transition table elements are assumed to be
0. 0.
4.2.5. colorspace_type 4.2.5. colorspace_type
"colorspace_type" specifies the color space encoded, the pixel "colorspace_type" specifies the color space encoded, the pixel
transformation used by the encoder, the extra plane content, as well transformation used by the encoder, the extra plane content, as well
as interleave method. as interleave method.
+=======+=============+================+==============+=============+ +=======+==============+================+==============+============+
| value | color space | pixel | extra plane | interleave | | value | color space | pixel | extra plane | interleave |
| | encoded | transformation | content | method | | | encoded | transformation | content | method |
+=======+=============+================+==============+=============+ +=======+==============+================+==============+============+
| 0 | YCbCr | None | Transparency | "Plane" | | 0 | YCbCr | None | Transparency | Plane then |
| | | | | then | | | | | | Line |
| | | | | "Line" | +-------+--------------+----------------+--------------+------------+
+-------+-------------+----------------+--------------+-------------+ | 1 | RGB | JPEG2000-RCT | Transparency | Line then |
| 1 | RGB | JPEG2000-RCT | Transparency | "Line" | | | | | | Plane |
| | | | | then | +-------+--------------+----------------+--------------+------------+
| | | | | "Plane" | | Other | reserved | reserved for | reserved for | reserved |
+-------+-------------+----------------+--------------+-------------+ | | for future | future use | future use | for future |
| Other | reserved | reserved for | reserved for | reserved | | | use | | | use |
| | for future | future use | future use | for future | +-------+--------------+----------------+--------------+------------+
| | use | | | use |
+-------+-------------+----------------+--------------+-------------+
Table 8 Table 8
FFV1 bitstreams with "colorspace_type" == 1 && ("chroma_planes" != FFV1 bitstreams with "colorspace_type" == 1 && ("chroma_planes" !=
1 || "log2_h_chroma_subsample" != 0 || "log2_v_chroma_subsample" != 1 || "log2_h_chroma_subsample" != 0 || "log2_v_chroma_subsample" !=
0) are not part of this specification. 0) are not part of this specification.
4.2.6. chroma_planes 4.2.6. chroma_planes
"chroma_planes" indicates if chroma (color) "Planes" are present. "chroma_planes" indicates if chroma (color) Planes are present.
+=======+=================================+ +=======+===============================+
| value | presence | | value | presence |
+=======+=================================+ +=======+===============================+
| 0 | chroma "Planes" are not present | | 0 | chroma Planes are not present |
+-------+---------------------------------+ +-------+-------------------------------+
| 1 | chroma "Planes" are present | | 1 | chroma Planes are present |
+-------+---------------------------------+ +-------+-------------------------------+
Table 9 Table 9
4.2.7. bits_per_raw_sample 4.2.7. bits_per_raw_sample
"bits_per_raw_sample" indicates the number of bits for each "Sample". "bits_per_raw_sample" indicates the number of bits for each Sample.
Inferred to be 8 if not present. Inferred to be 8 if not present.
+=======+===================================+ +=======+=================================+
| value | bits for each sample | | value | bits for each sample |
+=======+===================================+ +=======+=================================+
| 0 | reserved* | | 0 | reserved* |
+-------+-----------------------------------+ +-------+---------------------------------+
| Other | the actual bits for each "Sample" | | Other | the actual bits for each Sample |
+-------+-----------------------------------+ +-------+---------------------------------+
Table 10 Table 10
* Encoders MUST NOT store "bits_per_raw_sample" = 0. Decoders SHOULD * Encoders MUST NOT store "bits_per_raw_sample" = 0. Decoders SHOULD
accept and interpret "bits_per_raw_sample" = 0 as 8. accept and interpret "bits_per_raw_sample" = 0 as 8.
4.2.8. log2_h_chroma_subsample 4.2.8. log2_h_chroma_subsample
"log2_h_chroma_subsample" indicates the subsample factor, stored in "log2_h_chroma_subsample" indicates the subsample factor, stored in
powers to which the number 2 must be raised, between luma and chroma powers to which the number 2 is raised, between luma and chroma width
width ("chroma_width = 2 ^ -log2_h_chroma_subsample * luma_width"). ("chroma_width = 2 ^ -log2_h_chroma_subsample * luma_width").
4.2.9. log2_v_chroma_subsample 4.2.9. log2_v_chroma_subsample
"log2_v_chroma_subsample" indicates the subsample factor, stored in "log2_v_chroma_subsample" indicates the subsample factor, stored in
powers to which the number 2 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 * height ("chroma_height = 2 ^ -log2_v_chroma_subsample *
luma_height"). luma_height").
4.2.10. extra_plane 4.2.10. extra_plane
"extra_plane" indicates if an extra "Plane" is present. "extra_plane" indicates if an extra Plane is present.
+=======+==============================+ +=======+============================+
| value | presence | | value | presence |
+=======+==============================+ +=======+============================+
| 0 | extra "Plane" is not present | | 0 | extra Plane is not present |
+-------+------------------------------+ +-------+----------------------------+
| 1 | extra "Plane" is present | | 1 | extra Plane is present |
+-------+------------------------------+ +-------+----------------------------+
Table 11 Table 11
4.2.11. num_h_slices 4.2.11. num_h_slices
"num_h_slices" indicates the number of horizontal elements of the "num_h_slices" indicates the number of horizontal elements of the
slice raster. slice raster.
Inferred to be 1 if not present. Inferred to be 1 if not present.
skipping to change at page 36, line 4 skipping to change at page 38, line 4
+-------+--------------------------------+ +-------+--------------------------------+
Table 12 Table 12
4.2.15. initial_state_delta 4.2.15. initial_state_delta
"initial_state_delta[ i ][ j ][ k ]" indicates the initial Range "initial_state_delta[ i ][ j ][ k ]" indicates the initial Range
coder state, it is encoded using "k" as context index and coder state, it is encoded using "k" as context index and
pred = j ? initial_states[ i ][j - 1][ k ] : 128 pred = j ? initial_states[ i ][j - 1][ k ] : 128
Figure 23 Figure 26
initial_state[ i ][ j ][ k ] = initial_state[ i ][ j ][ k ] =
( pred + initial_state_delta[ i ][ j ][ k ] ) & 255 ( pred + initial_state_delta[ i ][ j ][ k ] ) & 255
Figure 24 Figure 27
4.2.16. ec 4.2.16. ec
"ec" indicates the error detection/correction type. "ec" indicates the error detection/correction type.
+=======+=================================================+ +=======+=================================================+
| value | error detection/correction type | | value | error detection/correction type |
+=======+=================================================+ +=======+=================================================+
| 0 | 32-bit CRC in "ConfigurationRecord" | | 0 | 32-bit CRC in "ConfigurationRecord" |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| 1 | 32-bit CRC in "Slice" and "ConfigurationRecord" | | 1 | 32-bit CRC in "Slice" and "ConfigurationRecord" |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------------------------------+ +-------+-------------------------------------------------+
Table 13 Table 13
4.2.17. intra 4.2.17. intra
"intra" indicates the constraint on "keyframe" in each instance of "intra" indicates the constraint on "keyframe" in each instance of
"Frame". Frame.
Inferred to be 0 if not present. Inferred to be 0 if not present.
+=======+=======================================================+ +=======+=======================================================+
| value | relationship | | value | relationship |
+=======+=======================================================+ +=======+=======================================================+
| 0 | "keyframe" can be 0 or 1 (non keyframes or keyframes) | | 0 | "keyframe" can be 0 or 1 (non keyframes or keyframes) |
+-------+-------------------------------------------------------+ +-------+-------------------------------------------------------+
| 1 | "keyframe" MUST be 1 (keyframes only) | | 1 | "keyframe" MUST be 1 (keyframes only) |
+-------+-------------------------------------------------------+ +-------+-------------------------------------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------------------------------------+ +-------+-------------------------------------------------------+
Table 14 Table 14
4.3. Configuration Record 4.3. Configuration Record
In the case of a FFV1 bitstream with "version >= 3", a "Configuration In the case of a FFV1 bitstream with "version >= 3", a "Configuration
Record" is stored in the underlying "Container" as described in Record" is stored in the underlying Container as described in
Section 4.3.3. It contains the "Parameters" used for all instances Section 4.3.3. It contains the "Parameters" used for all instances
of "Frame". The size of the "Configuration Record", "NumBytes", is of Frame. The size of the "Configuration Record", "NumBytes", is
supplied by the underlying "Container". supplied by the underlying Container.
pseudo-code | type pseudo-code | type
-----------------------------------------------------------|----- -----------------------------------------------------------|-----
ConfigurationRecord( NumBytes ) { | ConfigurationRecord( NumBytes ) { |
ConfigurationRecordIsPresent = 1 | ConfigurationRecordIsPresent = 1 |
Parameters( ) | Parameters( ) |
while (remaining_symbols_in_syntax(NumBytes - 4)) { | while (remaining_symbols_in_syntax(NumBytes - 4)) { |
reserved_for_future_use | br/ur/sr reserved_for_future_use | br/ur/sr
} | } |
configuration_record_crc_parity | u(32) configuration_record_crc_parity | u(32)
} | } |
4.3.1. reserved_for_future_use 4.3.1. reserved_for_future_use
"reserved_for_future_use" has semantics that are reserved for future "reserved_for_future_use" is a placeholder for future updates of this
use. specification.
Encoders conforming to this version of this specification SHALL NOT 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 Decoders conforming to this version of this specification SHALL
ignore its value. ignore "reserved_for_future_use".
4.3.2. configuration_record_crc_parity 4.3.2. configuration_record_crc_parity
"configuration_record_crc_parity" 32 bits that are chosen so that the "configuration_record_crc_parity" 32 bits that are chosen so that the
"Configuration Record" as a whole has a CRC remainder of 0. "Configuration Record" as a whole has a CRC remainder of 0.
This is equivalent to storing the CRC remainder in the 32-bit parity. This is equivalent to storing the CRC remainder in the 32-bit parity.
The CRC generator polynomial used is described in Section 4.9.3. The CRC generator polynomial used is described in Section 4.9.3.
skipping to change at page 38, line 49 skipping to change at page 40, line 49
versions 2 or less, the Matroska "CodecPrivate" Element SHOULD NOT be versions 2 or less, the Matroska "CodecPrivate" Element SHOULD NOT be
used. For FFV1 versions 3 or greater, the Matroska "CodecPrivate" used. For FFV1 versions 3 or greater, the Matroska "CodecPrivate"
Element MUST contain the FFV1 "Configuration Record" structure and no Element MUST contain the FFV1 "Configuration Record" structure and no
other data. See [Matroska] for more information about elements. other data. See [Matroska] for more information about elements.
"NumBytes" is defined as the "Element Data Size" of the "NumBytes" is defined as the "Element Data Size" of the
"CodecPrivate" Element. "CodecPrivate" Element.
4.4. Frame 4.4. Frame
A "Frame" is an encoded representation of a complete static image. A Frame is an encoded representation of a complete static image. The
The whole "Frame" is provided by the underlaying container. whole Frame is provided by the underlaying container.
A "Frame" consists of the "keyframe" field, "Parameters" (if A Frame consists of the "keyframe" field, "Parameters" (if "version"
"version" <= 1), and a sequence of independent slices. The pseudo- <= 1), and a sequence of independent slices. The pseudo-code below
code below describes the contents of a "Frame". describes the contents of a Frame.
"keyframe" field has its own initial state, set to 128. "keyframe" field has its own initial state, set to 128.
pseudo-code | type pseudo-code | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Frame( NumBytes ) { | Frame( NumBytes ) { |
keyframe | br keyframe | br
if (keyframe && !ConfigurationRecordIsPresent { | if (keyframe && !ConfigurationRecordIsPresent { |
Parameters( ) | Parameters( ) |
} | } |
while (remaining_bits_in_bitstream( NumBytes )) { | while (remaining_bits_in_bitstream( NumBytes )) { |
Slice( ) | Slice( ) |
} | } |
} | } |
Architecture overview of slices in a "Frame": Architecture overview of slices in a Frame:
+=================================================================+ +=================================================================+
+=================================================================+ +=================================================================+
| first slice header | | first slice header |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| first slice content | | first slice content |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| first slice footer | | first slice footer |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| --------------------------------------------------------------- | | --------------------------------------------------------------- |
skipping to change at page 40, line 38 skipping to change at page 42, line 38
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| last slice content | | last slice content |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
| last slice footer | | last slice footer |
+-----------------------------------------------------------------+ +-----------------------------------------------------------------+
Table 15 Table 15
4.5. Slice 4.5. Slice
A "Slice" is an independent spatial sub-section of a "Frame" that is A "Slice" is an independent spatial sub-section of a Frame that is
encoded separately from another region of the same "Frame". The use encoded separately from another region of the same Frame. The use of
of more than one "Slice" per "Frame" can be useful for taking more than one "Slice" per Frame can be useful for taking advantage of
advantage of the opportunities of multithreaded encoding and the opportunities of multithreaded encoding and decoding.
decoding.
A "Slice" consists of a "Slice Header" (when relevant), a "Slice A "Slice" consists of a "Slice Header" (when relevant), a "Slice
Content", and a "Slice Footer" (when relevant). The pseudo-code Content", and a "Slice Footer" (when relevant). The pseudo-code
below describes the contents of a "Slice". below describes the contents of a "Slice".
pseudo-code | type pseudo-code | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Slice( ) { | Slice( ) { |
if (version >= 3) { | if (version >= 3) { |
SliceHeader( ) | SliceHeader( ) |
skipping to change at page 41, line 34 skipping to change at page 43, line 34
} | } |
} | } |
"padding" specifies a bit without any significance and used only for "padding" specifies a bit without any significance and used only for
byte alignment. MUST be 0. byte alignment. MUST be 0.
"reserved" specifies a bit without any significance in this revision "reserved" specifies a bit without any significance in this revision
of the specification and may have a significance in a later revision of the specification and may have a significance in a later revision
of this specification. 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 4.6. Slice Header
A "Slice Header" provides information about the decoding A "Slice Header" provides information about the decoding
configuration of the "Slice", such as its spatial position, size, and configuration of the "Slice", such as its spatial position, size, and
aspect ratio. The pseudo-code below describes the contents of the aspect ratio. The pseudo-code below describes the contents of the
"Slice Header". "Slice Header".
"Slice Header" has its own initial states, all set to 128. "Slice Header" has its own initial states, all set to 128.
skipping to change at page 43, line 19 skipping to change at page 45, line 19
"quant_table_set_index" indicates the Quantization Table Set index to "quant_table_set_index" indicates the Quantization Table Set index to
select the Quantization Table Set and the initial states for the select the Quantization Table Set and the initial states for the
"Slice Content". "Slice Content".
Inferred to be 0 if not present. Inferred to be 0 if not present.
4.6.7. picture_structure 4.6.7. picture_structure
"picture_structure" specifies the temporal and spatial relationship "picture_structure" specifies the temporal and spatial relationship
of each "Line" of the "Frame". of each Line of the Frame.
Inferred to be 0 if not present. Inferred to be 0 if not present.
+=======+=========================+ +=======+=========================+
| value | picture structure used | | value | picture structure used |
+=======+=========================+ +=======+=========================+
| 0 | unknown | | 0 | unknown |
+-------+-------------------------+ +-------+-------------------------+
| 1 | top field first | | 1 | top field first |
+-------+-------------------------+ +-------+-------------------------+
skipping to change at page 43, line 41 skipping to change at page 45, line 41
+-------+-------------------------+ +-------+-------------------------+
| 3 | progressive | | 3 | progressive |
+-------+-------------------------+ +-------+-------------------------+
| Other | reserved for future use | | Other | reserved for future use |
+-------+-------------------------+ +-------+-------------------------+
Table 16 Table 16
4.6.8. sar_num 4.6.8. sar_num
"sar_num" specifies the "Sample" aspect ratio numerator. "sar_num" specifies the Sample aspect ratio numerator.
Inferred to be 0 if not present. Inferred to be 0 if not present.
A value of 0 means that aspect ratio is unknown. A value of 0 means that aspect ratio is unknown.
Encoders MUST write 0 if "Sample" aspect ratio is unknown. Encoders MUST write 0 if Sample aspect ratio is unknown.
If "sar_den" is 0, decoders SHOULD ignore the encoded value and If "sar_den" is 0, decoders SHOULD ignore the encoded value and
consider that "sar_num" is 0. consider that "sar_num" is 0.
4.6.9. sar_den 4.6.9. sar_den
"sar_den" specifies the "Sample" aspect ratio denominator. "sar_den" specifies the Sample aspect ratio denominator.
Inferred to be 0 if not present. Inferred to be 0 if not present.
A value of 0 means that aspect ratio is unknown. A value of 0 means that aspect ratio is unknown.
Encoders MUST write 0 if "Sample" aspect ratio is unknown. Encoders MUST write 0 if Sample aspect ratio is unknown.
If "sar_num" is 0, decoders SHOULD ignore the encoded value and If "sar_num" is 0, decoders SHOULD ignore the encoded value and
consider that "sar_den" is 0. consider that "sar_den" is 0.
4.7. Slice Content 4.7. Slice Content
A "Slice Content" contains all "Line" elements part of the "Slice". A "Slice Content" contains all Line elements part of the "Slice".
Depending on the configuration, "Line" elements are ordered by Depending on the configuration, Line elements are ordered by Plane
"Plane" then by row (YCbCr) or by row then by "Plane" (RGB). then by row (YCbCr) or by row then by Plane (RGB).
pseudo-code | type pseudo-code | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
SliceContent( ) { | SliceContent( ) { |
if (colorspace_type == 0) { | if (colorspace_type == 0) { |
for (p = 0; p < primary_color_count; p++) { | for (p = 0; p < primary_color_count; p++) { |
for (y = 0; y < plane_pixel_height[ p ]; y++) { | for (y = 0; y < plane_pixel_height[ p ]; y++) { |
Line( p, y ) | Line( p, y ) |
} | } |
} | } |
skipping to change at page 44, line 51 skipping to change at page 46, line 51
} | } |
4.7.1. primary_color_count 4.7.1. primary_color_count
"primary_color_count" is defined as: "primary_color_count" is defined as:
1 + ( chroma_planes ? 2 : 0 ) + ( extra_plane ? 1 : 0 ) 1 + ( chroma_planes ? 2 : 0 ) + ( extra_plane ? 1 : 0 )
4.7.2. plane_pixel_height 4.7.2. plane_pixel_height
"plane_pixel_height[ p ]" is the height in "Pixels" of "Plane" p of "plane_pixel_height[ p ]" is the height in Pixels of Plane p of the
the "Slice". It is defined as: "Slice". It is defined as:
chroma_planes == 1 && (p == 1 || p == 2) chroma_planes == 1 && (p == 1 || p == 2)
? ceil(slice_pixel_height / (1 << log2_v_chroma_subsample)) ? ceil(slice_pixel_height / (1 << log2_v_chroma_subsample))
: slice_pixel_height : slice_pixel_height
4.7.3. slice_pixel_height 4.7.3. slice_pixel_height
"slice_pixel_height" is the height in pixels of the slice. It is "slice_pixel_height" is the height in pixels of the slice. It is
defined as: defined as:
skipping to change at page 45, line 29 skipping to change at page 47, line 29
4.7.4. slice_pixel_y 4.7.4. slice_pixel_y
"slice_pixel_y" is the slice vertical position in pixels. It is "slice_pixel_y" is the slice vertical position in pixels. It is
defined as: defined as:
floor( slice_y * frame_pixel_height / num_v_slices ) floor( slice_y * frame_pixel_height / num_v_slices )
4.8. Line 4.8. Line
A "Line" is a list of the sample differences (relative to the A Line is a list of the sample differences (relative to the
predictor) of primary color components. The pseudo-code below predictor) of primary color components. The pseudo-code below
describes the contents of the "Line". describes the contents of the Line.
pseudo-code | type pseudo-code | type
--------------------------------------------------------------|----- --------------------------------------------------------------|-----
Line( p, y ) { | Line( p, y ) { |
if (colorspace_type == 0) { | if (colorspace_type == 0) { |
for (x = 0; x < plane_pixel_width[ p ]; x++) { | for (x = 0; x < plane_pixel_width[ p ]; x++) { |
sample_difference[ p ][ y ][ x ] | sd sample_difference[ p ][ y ][ x ] | sd
} | } |
} else if (colorspace_type == 1) { | } else if (colorspace_type == 1) { |
for (x = 0; x < slice_pixel_width; x++) { | for (x = 0; x < slice_pixel_width; x++) { |
sample_difference[ p ][ y ][ x ] | sd sample_difference[ p ][ y ][ x ] | sd
} | } |
} | } |
} | } |
4.8.1. plane_pixel_width 4.8.1. plane_pixel_width
"plane_pixel_width[ p ]" is the width in "Pixels" of "Plane" p of the "plane_pixel_width[ p ]" is the width in Pixels of Plane p of the
"Slice". It is defined as: "Slice". It is defined as:
chroma\_planes == 1 && (p == 1 || p == 2) chroma\_planes == 1 && (p == 1 || p == 2)
? ceil( slice_pixel_width / (1 << log2_h_chroma_subsample) ) ? ceil( slice_pixel_width / (1 << log2_h_chroma_subsample) )
: slice_pixel_width. : slice_pixel_width.
4.8.2. slice_pixel_width 4.8.2. slice_pixel_width
"slice_pixel_width" is the width in "Pixels" of the slice. It is "slice_pixel_width" is the width in Pixels of the slice. It is
defined as: defined as:
floor( floor(
( slice_x + slice_width ) ( slice_x + slice_width )
* slice_pixel_width * slice_pixel_width
/ num_h_slices / num_h_slices
) - slice_pixel_x ) - slice_pixel_x
4.8.3. slice_pixel_x 4.8.3. slice_pixel_x
"slice_pixel_x" is the slice horizontal position in "Pixels". It is "slice_pixel_x" is the slice horizontal position in Pixels. It is
defined as: defined as:
floor( slice_x * frame_pixel_width / num_h_slices ) floor( slice_x * frame_pixel_width / num_h_slices )
4.8.4. sample_difference 4.8.4. sample_difference
"sample_difference[ p ][ y ][ x ]" is the sample difference for "sample_difference[ p ][ y ][ x ]" is the sample difference for
"Sample" at "Plane" "p", y position "y", and x position "x". The Sample at Plane "p", y position "y", and x position "x". The Sample
"Sample" value is computed based on median predictor and context value is computed based on median predictor and context described in
described in Section 3.2. Section 3.2.
4.9. Slice Footer 4.9. Slice Footer
A "Slice Footer" provides information about slice size and A "Slice Footer" provides information about slice size and
(optionally) parity. The pseudo-code below describes the contents of (optionally) parity. The pseudo-code below describes the contents of
the "Slice Footer". the "Slice Footer".
Note: "Slice Footer" is always byte aligned. Note: "Slice Footer" is always byte aligned.
pseudo-code | type pseudo-code | type
skipping to change at page 47, line 48 skipping to change at page 49, line 48
The CRC generator polynomial used is the standard IEEE CRC polynomial The CRC generator polynomial used is the standard IEEE CRC polynomial
(0x104C11DB7), with initial value 0, without pre-inversion and (0x104C11DB7), with initial value 0, without pre-inversion and
without post-inversion. without post-inversion.
5. Restrictions 5. Restrictions
To ensure that fast multithreaded decoding is possible, starting with To ensure that fast multithreaded decoding is possible, starting with
version 3 and if "frame_pixel_width * frame_pixel_height" is more version 3 and if "frame_pixel_width * frame_pixel_height" is more
than 101376, "slice_width * slice_height" MUST be less or equal to 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 "num_h_slices * num_v_slices / 4". Note: 101376 is the frame size in
"Pixels" of a 352x288 frame also known as CIF ("Common Intermediate Pixels of a 352x288 frame also known as CIF ("Common Intermediate
Format") frame size format. Format") frame size format.
For each "Frame", each position in the slice raster MUST be filled by For each Frame, each position in the slice raster MUST be filled by
one and only one slice of the "Frame" (no missing slice position, no one and only one slice of the Frame (no missing slice position, no
slice overlapping). 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 same value of "slice_x", "slice_y", "slice_width", "slice_height" as
a slice in the previous "Frame". a slice in the previous Frame.
6. Security Considerations 6. Security Considerations
Like any other codec, (such as [RFC6716]), FFV1 should not be used Like any other codec, (such as [RFC6716]), FFV1 should not be used
with insecure ciphers or cipher-modes that are vulnerable to known with insecure ciphers or cipher-modes that are vulnerable to known
plaintext attacks. Some of the header bits as well as the padding plaintext attacks. Some of the header bits as well as the padding
are easily predictable. are easily predictable.
Implementations of the FFV1 codec need to take appropriate security Implementations of the FFV1 codec need to take appropriate security
considerations into account, as outlined in [RFC4732]. It is considerations into account, as outlined in [RFC4732]. It is
extremely important for the decoder to be robust against malicious 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 its allocated memory or to take an excessive amount of resources to
decode. The same applies to the encoder, even though problems in 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 the encoder to misbehave because this would allow an attacker to
attack transcoding gateways. A frequent security problem in image attack transcoding gateways. A frequent security problem in image
and video codecs is also to not check for integer overflows, for and video codecs is failure to check for integer overflows. An
example to allocate "frame_pixel_width * frame_pixel_height" in example is allocating "frame_pixel_width * frame_pixel_height" in
"Pixel" count computations without considering that the Pixel count computations without considering that the multiplication
multiplication result may have overflowed the arithmetic types range. result may have overflowed the arithmetic types range. The range
The range coder could, if implemented naively, read one byte over the coder could, if implemented naively, read one byte over the end. The
end. The implementation must ensure that no read outside allocated implementation MUST ensure that no read outside allocated and
and initialized memory occurs. initialized memory occurs.
None of the content carried in FFV1 is intended to be executable. None of the content carried in FFV1 is intended to be executable.
The reference implementation [REFIMPL] contains no known buffer The reference implementation [REFIMPL] contains no known buffer
overflow or cases where a specially crafted packet or video segment overflow or cases where a specially crafted packet or video segment
could cause a significant increase in CPU load. could cause a significant increase in CPU load.
The reference implementation [REFIMPL] was validated in the following The reference implementation [REFIMPL] was validated in the following
conditions: conditions:
skipping to change at page 49, line 13 skipping to change at page 51, line 13
then subjected to random corruption. then subjected to random corruption.
* Sending the decoder random packets that are not FFV1. * Sending the decoder random packets that are not FFV1.
In all of the conditions above, the decoder and encoder was run In all of the conditions above, the decoder and encoder was run
inside the [VALGRIND] memory debugger as well as clangs address inside the [VALGRIND] memory debugger as well as clangs address
sanitizer [Address-Sanitizer], which track reads and writes to sanitizer [Address-Sanitizer], which track reads and writes to
invalid memory regions as well as the use of uninitialized memory. invalid memory regions as well as the use of uninitialized memory.
There were no errors reported on any of the tested conditions. There were no errors reported on any of the tested conditions.
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 This registration is done using the template defined in [RFC6838] and
following [RFC4855]. following [RFC4855].
Type name: video Type name: video
Subtype name: FFV1 Subtype name: FFV1
Required parameters: None. Required parameters: None.
skipping to change at page 50, line 32 skipping to change at page 52, line 39
Niedermayer michael@niedermayer.cc (mailto:michael@niedermayer.cc) Niedermayer michael@niedermayer.cc (mailto:michael@niedermayer.cc)
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: None. Restrictions on usage: None.
Author: Dave Rice dave@dericed.com (mailto:dave@dericed.com) Author: Dave Rice dave@dericed.com (mailto:dave@dericed.com)
Change controller: IETF cellar working group delegated from the IESG. Change controller: IETF cellar working group delegated from the IESG.
8. IANA Considerations 8. Changelog
The IANA is requested to register the following values:
* Media type registration as described in Section 7.
9. Changelog
See https://github.com/FFmpeg/FFV1/commits/master See https://github.com/FFmpeg/FFV1/commits/master
(https://github.com/FFmpeg/FFV1/commits/master) (https://github.com/FFmpeg/FFV1/commits/master)
[RFC Editor: Please remove this Changelog section prior to [RFC Editor: Please remove this Changelog section prior to
publication.] publication.]
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, <https://datatracker.ietf.org/doc/
draft-ietf-cellar-matroska/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[ISO.9899.2018] [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
International Organization for Standardization, Denial-of-Service Considerations", RFC 4732,
"Programming languages - C", ISO Standard 9899, 2018. DOI 10.17487/RFC4732, December 2006,
<https://www.rfc-editor.org/info/rfc4732>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC4855] Casner, S., "Media Type Registration of RTP Payload
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. <https://www.rfc-editor.org/info/rfc4855>.
[RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the [RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the
Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716, Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716,
September 2012, <https://www.rfc-editor.org/info/rfc6716>. September 2012, <https://www.rfc-editor.org/info/rfc6716>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013, RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>. <https://www.rfc-editor.org/info/rfc6838>.
[RFC4855] Casner, S., "Media Type Registration of RTP Payload [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
<https://www.rfc-editor.org/info/rfc4855>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[ISO.9899.1990]
International Organization for Standardization,
"Programming languages - C", ISO Standard 9899, 1990.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732,
DOI 10.17487/RFC4732, December 2006,
<https://www.rfc-editor.org/info/rfc4732>.
[Matroska] IETF, "Matroska", 2019, <https://datatracker.ietf.org/doc/
draft-ietf-cellar-matroska/>.
[ISO.15444-1.2016]
International Organization for Standardization,
"Information technology -- JPEG 2000 image coding system:
Core coding system", October 2016.
11. Informative References
[AVI] Microsoft, "AVI RIFF File Reference", undated,
<https://msdn.microsoft.com/en-us/library/windows/desktop/
dd318189%28v=vs.85%29.aspx>.
[NUT] Niedermayer, M., "NUT Open Container Format", December
2013, <https://ffmpeg.org/~michael/nut.txt>.
[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.
[REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the 10. Informative References
FFV1 codec in FFmpeg", undated, <https://ffmpeg.org>.
[Address-Sanitizer] [Address-Sanitizer]
The Clang Team, "ASAN AddressSanitizer website", undated, The Clang Team, "ASAN AddressSanitizer website", undated,
<https://clang.llvm.org/docs/AddressSanitizer.html>. <https://clang.llvm.org/docs/AddressSanitizer.html>.
[ISO.14496-10.2014] [AVI] Microsoft, "AVI RIFF File Reference", undated,
International Organization for Standardization, <https://msdn.microsoft.com/en-us/library/windows/desktop/
"Information technology -- Coding of audio-visual objects dd318189%28v=vs.85%29.aspx>.
-- Part 10: Advanced Video Coding", September 2014.
[VALGRIND] Valgrind Developers, "Valgrind website", undated,
<https://valgrind.org/>.
[FFV1_V0] Niedermayer, M., "Commit to mark FFV1 version 0 as non- [FFV1_V0] Niedermayer, M., "Commit to mark FFV1 version 0 as non-
experimental", April 2006, <https://git.videolan.org/?p=ff experimental", April 2006, <https://git.videolan.org/?p=ff
mpeg.git;a=commit;h=b548f2b91b701e1235608ac882ea6df915167c mpeg.git;a=commit;h=b548f2b91b701e1235608ac882ea6df915167c
7e>. 7e>.
[FFV1_V1] Niedermayer, M., "Commit to release FFV1 version 1", April [FFV1_V1] Niedermayer, M., "Commit to release FFV1 version 1", April
2009, <https://git.videolan.org/?p=ffmpeg.git;a=commit;h=6 2009, <https://git.videolan.org/?p=ffmpeg.git;a=commit;h=6
8f8d33becbd73b4d0aa277f472a6e8e72ea6849>. 8f8d33becbd73b4d0aa277f472a6e8e72ea6849>.
[ISO.14495-1.1999] [FFV1_V3] Niedermayer, M., "Commit to mark FFV1 version 3 as non-
International Organization for Standardization, experimental", August 2013, <https://git.videolan.org/?p=f
"Information technology -- Lossless and near-lossless fmpeg.git;a=commit;h=abe76b851c05eea8743f6c899cbe5f7409b0f
compression of continuous-tone still images: Baseline", 301>.
December 1999.
[HuffYUV] Rudiak-Gould, B., "HuffYUV", December 2003, [HuffYUV] Rudiak-Gould, B., "HuffYUV", December 2003,
<https://web.archive.org/web/20040402121343/ <https://web.archive.org/web/20040402121343/
http://cultact-server.novi.dk/kpo/huffyuv/huffyuv.html>. http://cultact-server.novi.dk/kpo/huffyuv/huffyuv.html>.
[FFV1_V3] Niedermayer, M., "Commit to mark FFV1 version 3 as non- [ISO.14495-1.1999]
experimental", August 2013, <https://git.videolan.org/?p=f International Organization for Standardization,
fmpeg.git;a=commit;h=abe76b851c05eea8743f6c899cbe5f7409b0f "Information technology -- Lossless and near-lossless
301>. compression of continuous-tone still images: Baseline",
December 1999.
[YCbCr] Wikipedia, "YCbCr", undated, [ISO.14496-10.2014]
<https://en.wikipedia.org/w/index.php?title=YCbCr>. International Organization for Standardization,
"Information technology -- Coding of audio-visual objects
-- Part 10: Advanced Video Coding", September 2014.
[ISO.14496-12.2015] [ISO.14496-12.2015]
International Organization for Standardization, International Organization for Standardization,
"Information technology -- Coding of audio-visual objects "Information technology -- Coding of audio-visual objects
-- Part 12: ISO base media file format", December 2015. -- Part 12: ISO base media file format", December 2015.
[NUT] Niedermayer, M., "NUT Open Container Format", December
2013, <https://ffmpeg.org/~michael/nut.txt>.
[range-coding]
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.
[REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the
FFV1 codec in FFmpeg", undated, <https://ffmpeg.org>.
[VALGRIND] Valgrind Developers, "Valgrind website", undated,
<https://valgrind.org/>.
[YCbCr] Wikipedia, "YCbCr", undated,
<https://en.wikipedia.org/w/index.php?title=YCbCr>.
Appendix A. Multi-theaded decoder implementation suggestions Appendix A. Multi-theaded decoder implementation suggestions
This appendix is informative. This appendix is informative.
The FFV1 bitstream is parsable in two ways: in sequential order as The FFV1 bitstream is parsable in two ways: in sequential order as
described in this document or with the pre-analysis of the footer of described in this document or with the pre-analysis of the footer of
each slice. Each slice footer contains a "slice_size" field so the each slice. Each slice footer contains a "slice_size" field so the
boundary of each slice is computable without having to parse the boundary of each slice is computable without having to parse the
slice content. That allows multi-threading as well as independence slice content. That allows multi-threading as well as independence
of slice content (a bitstream error in a slice header or slice of slice content (a bitstream error in a slice header or slice
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