draft-ietf-cellar-ffv1-v4-13.txt		draft-ietf-cellar-ffv1-v4-14.txt
	cellar M. Niedermayer		cellar M. Niedermayer
	Internet-Draft		Internet-Draft
	Intended status: Standards Track D. Rice		Intended status: Standards Track D. Rice
	Expires: 3 January 2021		Expires: 22 February 2021
	J. Martinez		J. Martinez
	2 July 2020		21 August 2020
	FFV1 Video Coding Format Version 4		FFV1 Video Coding Format Version 4
	draft-ietf-cellar-ffv1-v4-13		draft-ietf-cellar-ffv1-v4-14
	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 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on 3 January 2021.		This Internet-Draft will expire on 22 February 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
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 28 ¶		skipping to change at page 2, line 28 ¶
	2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4		2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
	2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 5		2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 5
	2.2.1. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 5		2.2.1. Pseudo-code . . . . . . . . . . . . . . . . . . . . . 5
	2.2.2. Arithmetic Operators . . . . . . . . . . . . . . . . 6		2.2.2. Arithmetic Operators . . . . . . . . . . . . . . . . 6
	2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 6		2.2.3. Assignment Operators . . . . . . . . . . . . . . . . 6
	2.2.4. Comparison Operators . . . . . . . . . . . . . . . . 7		2.2.4. Comparison Operators . . . . . . . . . . . . . . . . 7
	2.2.5. Mathematical Functions . . . . . . . . . . . . . . . 7		2.2.5. Mathematical Functions . . . . . . . . . . . . . . . 7
	2.2.6. Order of Operation Precedence . . . . . . . . . . . . 8		2.2.6. Order of Operation Precedence . . . . . . . . . . . . 8
	2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 8		2.2.7. Range . . . . . . . . . . . . . . . . . . . . . . . . 8
	2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 8		2.2.8. NumBytes . . . . . . . . . . . . . . . . . . . . . . 8
	2.2.9. Bitstream Functions . . . . . . . . . . . . . . . . . 8		2.2.9. Bitstream Functions . . . . . . . . . . . . . . . . . 9
	3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 9		3. Sample Coding . . . . . . . . . . . . . . . . . . . . . . . . 9
	3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 9		3.1. Border . . . . . . . . . . . . . . . . . . . . . . . . . 9
	3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 10		3.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 10
	3.3. Median Predictor . . . . . . . . . . . . . . . . . . . . 11		3.3. Median Predictor . . . . . . . . . . . . . . . . . . . . 11
	3.4. Context . . . . . . . . . . . . . . . . . . . . . . . . . 11		3.4. Quantization Table Sets . . . . . . . . . . . . . . . . . 12
	3.5. Quantization Table Sets . . . . . . . . . . . . . . . . . 12		3.5. Context . . . . . . . . . . . . . . . . . . . . . . . . . 12
	3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 12		3.6. Quantization Table Set Indexes . . . . . . . . . . . . . 12
	3.7. Color spaces . . . . . . . . . . . . . . . . . . . . . . 12		3.7. Color spaces . . . . . . . . . . . . . . . . . . . . . . 13
	3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 13		3.7.1. YCbCr . . . . . . . . . . . . . . . . . . . . . . . . 13
	3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 13		3.7.2. RGB . . . . . . . . . . . . . . . . . . . . . . . . . 13
	3.8. Coding of the Sample Difference . . . . . . . . . . . . . 15		3.8. Coding of the Sample Difference . . . . . . . . . . . . . 15
	3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 15		3.8.1. Range Coding Mode . . . . . . . . . . . . . . . . . . 15
	3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 20		3.8.2. Golomb Rice Mode . . . . . . . . . . . . . . . . . . 21
	4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 25		4. Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . 26
	4.1. Quantization Table Set . . . . . . . . . . . . . . . . . 26		4.1. Quantization Table Set . . . . . . . . . . . . . . . . . 27
	4.1.1. quant_tables . . . . . . . . . . . . . . . . . . . . 27		4.1.1. quant_tables . . . . . . . . . . . . . . . . . . . . 28
	4.1.2. context_count . . . . . . . . . . . . . . . . . . . . 28		4.1.2. context_count . . . . . . . . . . . . . . . . . . . . 29
	4.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 28		4.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 29
	4.2.1. version . . . . . . . . . . . . . . . . . . . . . . . 30		4.2.1. version . . . . . . . . . . . . . . . . . . . . . . . 31
	4.2.2. micro_version . . . . . . . . . . . . . . . . . . . . 30		4.2.2. micro_version . . . . . . . . . . . . . . . . . . . . 31
	4.2.3. coder_type . . . . . . . . . . . . . . . . . . . . . 31		4.2.3. coder_type . . . . . . . . . . . . . . . . . . . . . 32
	4.2.4. state_transition_delta . . . . . . . . . . . . . . . 32		4.2.4. state_transition_delta . . . . . . . . . . . . . . . 33
	4.2.5. colorspace_type . . . . . . . . . . . . . . . . . . . 32		4.2.5. colorspace_type . . . . . . . . . . . . . . . . . . . 33
	4.2.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 33		4.2.6. chroma_planes . . . . . . . . . . . . . . . . . . . . 34
	4.2.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 33		4.2.7. bits_per_raw_sample . . . . . . . . . . . . . . . . . 34
	4.2.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 34		4.2.8. log2_h_chroma_subsample . . . . . . . . . . . . . . . 35
	4.2.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 34		4.2.9. log2_v_chroma_subsample . . . . . . . . . . . . . . . 35
	4.2.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 34		4.2.10. extra_plane . . . . . . . . . . . . . . . . . . . . . 35
	4.2.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 34		4.2.11. num_h_slices . . . . . . . . . . . . . . . . . . . . 35
	4.2.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 35		4.2.12. num_v_slices . . . . . . . . . . . . . . . . . . . . 36
	4.2.13. quant_table_set_count . . . . . . . . . . . . . . . . 35		4.2.13. quant_table_set_count . . . . . . . . . . . . . . . . 36
	4.2.14. states_coded . . . . . . . . . . . . . . . . . . . . 35		4.2.14. states_coded . . . . . . . . . . . . . . . . . . . . 36
	4.2.15. initial_state_delta . . . . . . . . . . . . . . . . . 35		4.2.15. initial_state_delta . . . . . . . . . . . . . . . . . 36
	4.2.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 36		4.2.16. ec . . . . . . . . . . . . . . . . . . . . . . . . . 37
	4.2.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 36		4.2.17. intra . . . . . . . . . . . . . . . . . . . . . . . . 37
	4.3. Configuration Record . . . . . . . . . . . . . . . . . . 36		4.3. Configuration Record . . . . . . . . . . . . . . . . . . 37
	4.3.1. reserved_for_future_use . . . . . . . . . . . . . . . 37		4.3.1. reserved_for_future_use . . . . . . . . . . . . . . . 38
	4.3.2. configuration_record_crc_parity . . . . . . . . . . . 37		4.3.2. configuration_record_crc_parity . . . . . . . . . . . 38
	4.3.3. Mapping FFV1 into Containers . . . . . . . . . . . . 37		4.3.3. Mapping FFV1 into Containers . . . . . . . . . . . . 38
	4.4. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 38		4.4. Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 39
	4.5. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 40		4.5. Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 41
	4.6. Slice Header . . . . . . . . . . . . . . . . . . . . . . 41		4.6. Slice Header . . . . . . . . . . . . . . . . . . . . . . 42
	4.6.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 41		4.6.1. slice_x . . . . . . . . . . . . . . . . . . . . . . . 42
	4.6.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 41		4.6.2. slice_y . . . . . . . . . . . . . . . . . . . . . . . 42
	4.6.3. slice_width . . . . . . . . . . . . . . . . . . . . . 41		4.6.3. slice_width . . . . . . . . . . . . . . . . . . . . . 42
	4.6.4. slice_height . . . . . . . . . . . . . . . . . . . . 42		4.6.4. slice_height . . . . . . . . . . . . . . . . . . . . 43
	4.6.5. quant_table_set_index_count . . . . . . . . . . . . . 42		4.6.5. quant_table_set_index_count . . . . . . . . . . . . . 43
	4.6.6. quant_table_set_index . . . . . . . . . . . . . . . . 42		4.6.6. quant_table_set_index . . . . . . . . . . . . . . . . 43
	4.6.7. picture_structure . . . . . . . . . . . . . . . . . . 42		4.6.7. picture_structure . . . . . . . . . . . . . . . . . . 43
	4.6.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 43		4.6.8. sar_num . . . . . . . . . . . . . . . . . . . . . . . 44
	4.6.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 43		4.6.9. sar_den . . . . . . . . . . . . . . . . . . . . . . . 44
	4.6.10. reset_contexts . . . . . . . . . . . . . . . . . . . 43		4.6.10. reset_contexts . . . . . . . . . . . . . . . . . . . 44
	4.6.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 43		4.6.11. slice_coding_mode . . . . . . . . . . . . . . . . . . 44
	4.7. Slice Content . . . . . . . . . . . . . . . . . . . . . . 44		4.7. Slice Content . . . . . . . . . . . . . . . . . . . . . . 45
	4.7.1. primary_color_count . . . . . . . . . . . . . . . . . 44		4.7.1. primary_color_count . . . . . . . . . . . . . . . . . 45
	4.7.2. plane_pixel_height . . . . . . . . . . . . . . . . . 44		4.7.2. plane_pixel_height . . . . . . . . . . . . . . . . . 45
	4.7.3. slice_pixel_height . . . . . . . . . . . . . . . . . 45		4.7.3. slice_pixel_height . . . . . . . . . . . . . . . . . 46
	4.7.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 45		4.7.4. slice_pixel_y . . . . . . . . . . . . . . . . . . . . 46
	4.8. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 45		4.8. Line . . . . . . . . . . . . . . . . . . . . . . . . . . 46
	4.8.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 45		4.8.1. plane_pixel_width . . . . . . . . . . . . . . . . . . 46
	4.8.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 46		4.8.2. slice_pixel_width . . . . . . . . . . . . . . . . . . 47
	4.8.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 46		4.8.3. slice_pixel_x . . . . . . . . . . . . . . . . . . . . 47
	4.8.4. sample_difference . . . . . . . . . . . . . . . . . . 46		4.8.4. sample_difference . . . . . . . . . . . . . . . . . . 47
	4.9. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 46		4.9. Slice Footer . . . . . . . . . . . . . . . . . . . . . . 47
	4.9.1. slice_size . . . . . . . . . . . . . . . . . . . . . 47		4.9.1. slice_size . . . . . . . . . . . . . . . . . . . . . 48
	4.9.2. error_status . . . . . . . . . . . . . . . . . . . . 47		4.9.2. error_status . . . . . . . . . . . . . . . . . . . . 48
	4.9.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 47		4.9.3. slice_crc_parity . . . . . . . . . . . . . . . . . . 48
	5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 47		5. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 48
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 48		6. Security Considerations . . . . . . . . . . . . . . . . . . . 49
	7. Media Type Definition . . . . . . . . . . . . . . . . . . . . 49		7. Media Type Definition . . . . . . . . . . . . . . . . . . . . 50
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 51
	9. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 50		9. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 51
	10. Normative References . . . . . . . . . . . . . . . . . . . . 50		10. Normative References . . . . . . . . . . . . . . . . . . . . 51
	11. Informative References . . . . . . . . . . . . . . . . . . . 51		11. Informative References . . . . . . . . . . . . . . . . . . . 52
	Appendix A. Multi-theaded decoder implementation suggestions . . 52		Appendix A. Multi-theaded decoder implementation suggestions . . 54
	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 . . . . . . . . . . . . . . . . . . . 54
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54
	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
	skipping to change at page 8, line 14 ¶		skipping to change at page 8, line 14 ¶
	"max(a,b)" means the largest of two values a and b.		"max(a,b)" means the largest 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,c) means the 'b,c'-th value of a sequence of a
	2.2.6. Order of Operation Precedence		2.2.6. Order of Operation Precedence
	When order of precedence is not indicated explicitly by use of		When order of precedence is not indicated explicitly by use of
	parentheses, operations are evaluated in the following order (from		parentheses, operations are evaluated in the following order (from
	top to bottom, operations of same precedence being evaluated from		top to bottom, operations of same precedence being evaluated from
	left to right). This order of operations is based on the order of		left to right). This order of operations is based on the order of
	operations used in Standard C.		operations used in Standard C.
	a++, a--		a++, a--
	!a, -a		!a, -a
	skipping to change at page 11, line 43 ¶		skipping to change at page 12, line 5 ¶
	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.
	3.4. Context		3.4. Quantization Table Sets
	Relative to any "Sample" "X", the Quantized Sample Differences "L-l",
	"l-tl", "tl-t", "T-t", and "t-tr" are used as context:
	context = Q_{0}[l - tl] +
	Q_{1}[tl - t] +
	Q_{2}[t - tr] +
	Q_{3}[L - l] +
	Q_{4}[T - t]
	Figure 4
	If "context >= 0" then "context" is used and the difference between
	the "Sample" and its predicted value is encoded as is, else
	"-context" is used and the difference between the "Sample" and its
	predicted value is encoded with a flipped sign.
	3.5. Quantization Table Sets
	The FFV1 bitstream contains one or more Quantization Table Sets.		The FFV1 bitstream contains one or more Quantization Table Sets.
	Each Quantization Table Set contains exactly 5 Quantization Tables		Each Quantization Table Set contains exactly 5 Quantization Tables
	with each Quantization Table corresponding to one of the five		with each Quantization Table corresponding to one of the five
	Quantized Sample Differences. For each Quantization Table, both the		Quantized Sample Differences. For each Quantization Table, both the
	number of quantization steps and their distribution are stored in the		number of quantization steps and their distribution are stored in the
	FFV1 bitstream; each Quantization Table has exactly 256 entries, and		FFV1 bitstream; each Quantization Table has exactly 256 entries, and
	the 8 least significant bits of the Quantized Sample Difference are		the 8 least significant bits of the Quantized Sample Difference are
	used as index:		used as index:
	Q_{j}[k] = quant_tables[i][j][k&255]		Q_(j)[k] = quant_tables[i][j][k&255]
	Figure 5		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
			Relative to any "Sample" "X", the Quantized Sample Differences "L-l",
			"l-tl", "tl-t", "T-t", and "t-tr" are used as context:
			context = Q_(0)[l - tl] +
			Q_(1)[tl - t] +
			Q_(2)[t - tr] +
			Q_(3)[L - l] +
			Q_(4)[T - t]
			Figure 5
			If "context >= 0" then "context" is used and the difference between
			the "Sample" and its predicted value is encoded as is, else
			"-context" is used and the difference between the "Sample" and its
			predicted value is encoded with a flipped sign.
	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 ||
	skipping to change at page 15, line 45 ¶		skipping to change at page 16, line 7 ¶
	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 and 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)"		the i-th Context. B_(i) is the i-th byte of the bytestream. b_(i) is
	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
	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) <==
	b_i = 1 <==>		b_(i) = 1 <==>
	L_i >= R_i - r_i		L_(i) >= R_(i) - r_(i)
	Figure 10		Figure 10
	S_{i+1,k} = S_{i,k} <== C_i != k		S_(i + 1, k) = S_(i, k) <== C_(i) != k
	Figure 11		Figure 11
	R_{i+1} = 2 ^ 8 * t_{i} AND		R_(i + 1) = 2 ^ 8 * t_(i) AND
	L_{i+1} = 2 ^ 8 * l_{i} + B_{j_{i}} AND		L_(i + 1) = 2 ^ 8 * l_(i) + B_(j_(i)) AND
	j_{i+1} = j_{i} + 1 <==		j_(i + 1) = j_(i) + 1 <==
	t_{i} < 2 ^ 8		t_(i) < 2 ^ 8
	R_{i+1} = t_{i} AND		R_(i + 1) = t_(i) AND
	L_{i+1} = l_{i} AND		L_(i + 1) = l_(i) AND
	j_{i+1} = j_{i} <==		j_(i + 1) = j_(i) <==
	t_{i} >= 2 ^ 8		t_(i) >= 2 ^ 8
	Figure 12		Figure 12
	R_{0} = 65280		R_(0) = 65280
	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
	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
	skipping to change at page 18, line 37 ¶		skipping to change at page 18, line 51 ¶
	return a;		return a;
	}		}
	}		}
	Figure 16: A pseudo-code description of the contexts of Range Non		Figure 16: 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" is the process described in Section 3.8.1.1.		"get_rac" returns a boolean, computed from the bytestream as
			described in Section 3.8.1.1.
	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		At keyframes all Range coder state variables are set to their initial
	state.		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 17
	zero_state_{i} = 256 - one_state_{256-i}		zero_state_(i) = 256 - one_state_(256-i)
	Figure 18		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 48, line 29 ¶		skipping to change at page 49, line 29 ¶
	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 in		and video codecs is also to not check for integer overflows, for
	"Pixel" count computations, that is to allocate width * height		example to allocate "frame_pixel_width * frame_pixel_height" in
	without considering that the multiplication result may have		"Pixel" count computations without considering that the
	overflowed the arithmetic types range. The range coder could, if		multiplication result may have overflowed the arithmetic types range.
	implemented naively, read one byte over the end. The implementation		The range coder could, if implemented naively, read one byte over the
	must ensure that no read outside allocated and initialized memory		end. The implementation must ensure that no read outside allocated
	occurs.		and initialized memory occurs.
			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:
	* Sending the decoder valid packets generated by the reference		* Sending the decoder valid packets generated by the reference
	encoder and verifying that the decoder's output matches the		encoder and verifying that the decoder's output matches the
	skipping to change at page 51, line 5 ¶		skipping to change at page 52, line 5 ¶
	[RFC Editor: Please remove this Changelog section prior to		[RFC Editor: Please remove this Changelog section prior to
	publication.]		publication.]
	10. Normative References		10. Normative References
	[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>.
			[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
			2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
			May 2017, <https://www.rfc-editor.org/info/rfc8174>.
			[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>.
			[ISO.9899.2018]
			International Organization for Standardization,
			"Programming languages - C", ISO Standard 9899, 2018.
			[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
			Specifications and Registration Procedures", BCP 13,
			RFC 6838, DOI 10.17487/RFC6838, January 2013,
			<https://www.rfc-editor.org/info/rfc6838>.
			[ISO.9899.1990]
			International Organization for Standardization,
			"Programming languages - C", ISO Standard 9899, 1990.
	[ISO.15444-1.2016]		[ISO.15444-1.2016]
	International Organization for Standardization,		International Organization for Standardization,
	"Information technology -- JPEG 2000 image coding system:		"Information technology -- JPEG 2000 image coding system:
	Core coding system", October 2016.		Core coding system", October 2016.
	[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>.
	[ISO.9899.2018]
	International Organization for Standardization,
	"Programming languages - C", 2018.
	[Matroska] IETF, "Matroska", 2019, <https://datatracker.ietf.org/doc/
	draft-ietf-cellar-matroska/>.
	[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>.
	[RFC4855] Casner, S., "Media Type Registration of RTP Payload		[RFC4855] Casner, S., "Media Type Registration of RTP Payload
	Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,		Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
	<https://www.rfc-editor.org/info/rfc4855>.		<https://www.rfc-editor.org/info/rfc4855>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[Matroska] IETF, "Matroska", 2019, <https://datatracker.ietf.org/doc/
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		draft-ietf-cellar-matroska/>.
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[ISO.9899.1990]
	International Organization for Standardization,
	"Programming languages - C", 1990.
	[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
	Specifications and Registration Procedures", BCP 13,
	RFC 6838, DOI 10.17487/RFC6838, January 2013,
	<https://www.rfc-editor.org/info/rfc6838>.
	11. Informative References		11. Informative References
	[YCbCr] Wikipedia, "YCbCr", undated,
	<https://en.wikipedia.org/w/index.php?title=YCbCr>.
	[I-D.ietf-cellar-ffv1]		[I-D.ietf-cellar-ffv1]
	Niedermayer, M., Rice, D., and J. Martinez, "FFV1 Video		Niedermayer, M., Rice, D., and J. Martinez, "FFV1 Video
	Coding Format Version 0, 1, and 3", Work in Progress,		Coding Format Version 0, 1, and 3", Work in Progress,
	Internet-Draft, draft-ietf-cellar-ffv1-14, 26 May 2020,		Internet-Draft, draft-ietf-cellar-ffv1-16, 2 July 2020,
	<https://tools.ietf.org/html/draft-ietf-cellar-ffv1-14>.		<https://tools.ietf.org/html/draft-ietf-cellar-ffv1-16>.
	[HuffYUV] Rudiak-Gould, B., "HuffYUV", December 2003,
	<https://web.archive.org/web/20040402121343/
	http://cultact-server.novi.dk/kpo/huffyuv/huffyuv.html>.
	[AVI] Microsoft, "AVI RIFF File Reference", undated,
	<https://msdn.microsoft.com/en-us/library/windows/desktop/
	dd318189%28v=vs.85%29.aspx>.
	[ISO.14496-12.2015]
	International Organization for Standardization,
	"Information technology -- Coding of audio-visual objects
	-- Part 12: ISO base media file format", December 2015.
	[ISO.14495-1.1999]		[ISO.14495-1.1999]
	International Organization for Standardization,		International Organization for Standardization,
	"Information technology -- Lossless and near-lossless		"Information technology -- Lossless and near-lossless
	compression of continuous-tone still images: Baseline",		compression of continuous-tone still images: Baseline",
	December 1999.		December 1999.
	[VALGRIND] Valgrind Developers, "Valgrind website", undated,		[NUT] Niedermayer, M., "NUT Open Container Format", December
	<https://valgrind.org/>.		2013, <https://ffmpeg.org/~michael/nut.txt>.
	[range-coding]		[YCbCr] Wikipedia, "YCbCr", undated,
	Nigel, G. and N. Martin, "Range encoding: an algorithm for		<https://en.wikipedia.org/w/index.php?title=YCbCr>.
	removing redundancy from a digitised message.", July 1979.
	[ISO.14496-10.2014]		[ISO.14496-10.2014]
	International Organization for Standardization,		International Organization for Standardization,
	"Information technology -- Coding of audio-visual objects		"Information technology -- Coding of audio-visual objects
	-- Part 10: Advanced Video Coding", September 2014.		-- Part 10: Advanced Video Coding", September 2014.
			[VALGRIND] Valgrind Developers, "Valgrind website", undated,
			<https://valgrind.org/>.
	[REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the		[REFIMPL] Niedermayer, M., "The reference FFV1 implementation / the
	FFV1 codec in FFmpeg", undated, <https://ffmpeg.org>.		FFV1 codec in FFmpeg", undated, <https://ffmpeg.org>.
			[HuffYUV] Rudiak-Gould, B., "HuffYUV", December 2003,
			<https://web.archive.org/web/20040402121343/
			http://cultact-server.novi.dk/kpo/huffyuv/huffyuv.html>.
			[ISO.14496-12.2015]
			International Organization for Standardization,
			"Information technology -- Coding of audio-visual objects
			-- Part 12: ISO base media file format", December 2015.
			[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.
			[AVI] Microsoft, "AVI RIFF File Reference", undated,
			<https://msdn.microsoft.com/en-us/library/windows/desktop/
			dd318189%28v=vs.85%29.aspx>.
	[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>.
	[NUT] Niedermayer, M., "NUT Open Container Format", December
	2013, <https://ffmpeg.org/~michael/nut.txt>.
	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
End of changes. 40 change blocks.
	183 lines changed or deleted		194 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/