< draft-bankoski-vp8-bitstream-03.txt		draft-bankoski-vp8-bitstream-04.txt >
	Network Working Group J. Bankoski		Network Working Group J. Bankoski
	Internet-Draft J. Koleszar		Internet-Draft J. Koleszar
	Intended status: Informational L. Quillio		Intended status: Informational L. Quillio
	Expires: December 17, 2011 J. Salonen		Expires: December 18, 2011 J. Salonen
	P. Wilkins		P. Wilkins
	Y. Xu		Y. Xu
	Google Inc.		Google Inc.
	June 15, 2011		June 16, 2011
	VP8 Data Format and Decoding Guide		VP8 Data Format and Decoding Guide
	draft-bankoski-vp8-bitstream-03		draft-bankoski-vp8-bitstream-04
	Abstract		Abstract
	This document describes the VP8 compressed video data format,		This document describes the VP8 compressed video data format,
	together with a discussion of the decoding procedure for the format.		together with a discussion of the decoding procedure for the format.
	Status of this Memo		Status of this Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	skipping to change at page 1, line 35 ¶		skipping to change at page 1, line 35 ¶
	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 http://datatracker.ietf.org/drafts/current/.		Drafts is at http://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 December 17, 2011.		This Internet-Draft will expire on December 18, 2011.
	Copyright Notice		Copyright Notice
	Copyright (c) 2011 IETF Trust and the persons identified as the		Copyright (c) 2011 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		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 3, line 27 ¶		skipping to change at page 3, line 27 ¶
	17.1. Coding of Each Component . . . . . . . . . . . . . . . . 117		17.1. Coding of Each Component . . . . . . . . . . . . . . . . 117
	17.2. Probability Updates . . . . . . . . . . . . . . . . . . 119		17.2. Probability Updates . . . . . . . . . . . . . . . . . . 119
	18. Interframe Prediction . . . . . . . . . . . . . . . . . . . . 122		18. Interframe Prediction . . . . . . . . . . . . . . . . . . . . 122
	18.1. Bounds on and Adjustment of Motion Vectors . . . . . . . 122		18.1. Bounds on and Adjustment of Motion Vectors . . . . . . . 122
	18.2. Prediction Subblocks . . . . . . . . . . . . . . . . . . 123		18.2. Prediction Subblocks . . . . . . . . . . . . . . . . . . 123
	18.3. Sub-pixel Interpolation . . . . . . . . . . . . . . . . 124		18.3. Sub-pixel Interpolation . . . . . . . . . . . . . . . . 124
	18.4. Filter Properties . . . . . . . . . . . . . . . . . . . 127		18.4. Filter Properties . . . . . . . . . . . . . . . . . . . 127
	19. Annex A: Bitstream Syntax . . . . . . . . . . . . . . . . . . 130		19. Annex A: Bitstream Syntax . . . . . . . . . . . . . . . . . . 130
	19.1. Uncompressed Data Chunk . . . . . . . . . . . . . . . . 130		19.1. Uncompressed Data Chunk . . . . . . . . . . . . . . . . 130
	19.2. Frame Header . . . . . . . . . . . . . . . . . . . . . . 132		19.2. Frame Header . . . . . . . . . . . . . . . . . . . . . . 132
	19.3. Macroblock Data . . . . . . . . . . . . . . . . . . . . 144		19.3. Macroblock Data . . . . . . . . . . . . . . . . . . . . 143
	20. Attachment One: Reference Decoder Source Code . . . . . . . . 148		20. Attachment One: Reference Decoder Source Code . . . . . . . . 147
	20.1. bit_ops.h . . . . . . . . . . . . . . . . . . . . . . . 148		20.1. bit_ops.h . . . . . . . . . . . . . . . . . . . . . . . 147
	20.2. bool_decoder.h . . . . . . . . . . . . . . . . . . . . . 148		20.2. bool_decoder.h . . . . . . . . . . . . . . . . . . . . . 147
	20.3. dequant_data.h . . . . . . . . . . . . . . . . . . . . . 152		20.3. dequant_data.h . . . . . . . . . . . . . . . . . . . . . 151
	20.4. dixie.c . . . . . . . . . . . . . . . . . . . . . . . . 152		20.4. dixie.c . . . . . . . . . . . . . . . . . . . . . . . . 151
	20.5. dixie.h . . . . . . . . . . . . . . . . . . . . . . . . 164		20.5. dixie.h . . . . . . . . . . . . . . . . . . . . . . . . 163
	20.6. dixie_loopfilter.c . . . . . . . . . . . . . . . . . . . 171		20.6. dixie_loopfilter.c . . . . . . . . . . . . . . . . . . . 170
	20.7. dixie_loopfilter.h . . . . . . . . . . . . . . . . . . . 183		20.7. dixie_loopfilter.h . . . . . . . . . . . . . . . . . . . 182
	20.8. idct_add.c . . . . . . . . . . . . . . . . . . . . . . . 183		20.8. idct_add.c . . . . . . . . . . . . . . . . . . . . . . . 182
	20.9. idct_add.h . . . . . . . . . . . . . . . . . . . . . . . 187		20.9. idct_add.h . . . . . . . . . . . . . . . . . . . . . . . 186
	20.10. mem.h . . . . . . . . . . . . . . . . . . . . . . . . . 187		20.10. mem.h . . . . . . . . . . . . . . . . . . . . . . . . . 186
	20.11. modemv.c . . . . . . . . . . . . . . . . . . . . . . . . 189		20.11. modemv.c . . . . . . . . . . . . . . . . . . . . . . . . 188
	20.12. modemv.h . . . . . . . . . . . . . . . . . . . . . . . . 204		20.12. modemv.h . . . . . . . . . . . . . . . . . . . . . . . . 203
	20.13. modemv_data.h . . . . . . . . . . . . . . . . . . . . . 204		20.13. modemv_data.h . . . . . . . . . . . . . . . . . . . . . 203
	20.14. predict.c . . . . . . . . . . . . . . . . . . . . . . . 209		20.14. predict.c . . . . . . . . . . . . . . . . . . . . . . . 208
	20.15. predict.h . . . . . . . . . . . . . . . . . . . . . . . 239		20.15. predict.h . . . . . . . . . . . . . . . . . . . . . . . 238
	20.16. tokens.c . . . . . . . . . . . . . . . . . . . . . . . . 239		20.16. tokens.c . . . . . . . . . . . . . . . . . . . . . . . . 238
	20.17. tokens.h . . . . . . . . . . . . . . . . . . . . . . . . 249		20.17. tokens.h . . . . . . . . . . . . . . . . . . . . . . . . 248
	20.18. vp8_prob_data.h . . . . . . . . . . . . . . . . . . . . 258		20.18. vp8_prob_data.h . . . . . . . . . . . . . . . . . . . . 257
	20.19. vpx_codec_internal.h . . . . . . . . . . . . . . . . . . 267		20.19. vpx_codec_internal.h . . . . . . . . . . . . . . . . . . 266
	20.20. vpx_decoder.h . . . . . . . . . . . . . . . . . . . . . 277		20.20. vpx_decoder.h . . . . . . . . . . . . . . . . . . . . . 276
	20.21. vpx_integer.h . . . . . . . . . . . . . . . . . . . . . 284		20.21. vpx_integer.h . . . . . . . . . . . . . . . . . . . . . 283
	20.22. AUTHORS . . . . . . . . . . . . . . . . . . . . . . . . 286		20.22. AUTHORS . . . . . . . . . . . . . . . . . . . . . . . . 285
	20.23. LICENSE . . . . . . . . . . . . . . . . . . . . . . . . 287		20.23. LICENSE . . . . . . . . . . . . . . . . . . . . . . . . 286
	20.24. PATENTS . . . . . . . . . . . . . . . . . . . . . . . . 288		20.24. PATENTS . . . . . . . . . . . . . . . . . . . . . . . . 287
	21. References . . . . . . . . . . . . . . . . . . . . . . . . . 290		21. References . . . . . . . . . . . . . . . . . . . . . . . . . 289
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 291		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 290
	1. Introduction		1. Introduction
	This document describes the VP8 compressed video data format,		This document describes the VP8 compressed video data format,
	together with a discussion of the decoding procedure for the format.		together with a discussion of the decoding procedure for the format.
	It is intended to be used in conjunction with and as a guide to the		It is intended to be used in conjunction with and as a guide to the
	reference decoder source code provided in Attachment One. If there		reference decoder source code provided in Attachment One. If there
	are any conflicts between this narrative and the reference source		are any conflicts between this narrative and the reference source
	code, the reference source code should be considered correct. The		code, the reference source code should be considered correct. The
	bitstream is defined by the reference source code and not this		bitstream is defined by the reference source code and not this
	skipping to change at page 11, line 33 ¶		skipping to change at page 11, line 33 ¶
	All partitions are decoded using separate instances of the boolean		All partitions are decoded using separate instances of the boolean
	entropy decoder described in Chapter 7. Although some of the data		entropy decoder described in Chapter 7. Although some of the data
	represented within the partitions is conceptually "flat" (a bit is		represented within the partitions is conceptually "flat" (a bit is
	just a bit with no probabilistic expectation one way or the other),		just a bit with no probabilistic expectation one way or the other),
	because of the way such coders work, there is never a direct		because of the way such coders work, there is never a direct
	correspondence between a "conceptual bit" and an actual physical bit		correspondence between a "conceptual bit" and an actual physical bit
	in the compressed data partitions. Only in the 3 or 10 byte		in the compressed data partitions. Only in the 3 or 10 byte
	uncompressed chunk described above is there such a physical		uncompressed chunk described above is there such a physical
	correspondence.		correspondence.
	A related matter, which is true for most lossless compression		A related matter is that seeking within a partition is not supported.
	formats, is that seeking within a partition is not supported. The		The data must be decompressed and processed (or at least stored) in
	data must be decompressed and processed (or at least stored) in the		the order in which it occurs in the partition.
	order in which it occurs in the partition.
	While this document specifies the ordering of the partition data		While this document specifies the ordering of the partition data
	correctly, the details and semantics of this data are discussed in a		correctly, the details and semantics of this data are discussed in a
	more logical fashion to facilitate comprehension. For example, the		more logical fashion to facilitate comprehension. For example, the
	frame header contains updates to many probability tables used in		frame header contains updates to many probability tables used in
	decoding per-macroblock data. The latter is often described before		decoding per-macroblock data. The latter is often described before
	the layouts of the probabilities and their updates, even though this		the layouts of the probabilities and their updates, even though this
	is the opposite of their order in the bitstream.		is the opposite of their order in the bitstream.
	5. Overview of the Decoding Process		5. Overview of the Decoding Process
	skipping to change at page 68, line 46 ¶		skipping to change at page 68, line 46 ¶
	cat2 = "111101" */		cat2 = "111101" */
	18, 20,		18, 20,
	-dct_cat3, -dct_cat4, /* cat3 = "1111100",		-dct_cat3, -dct_cat4, /* cat3 = "1111100",
	cat4 = "1111101" */		cat4 = "1111101" */
	-dct_cat5, -dct_cat6 /* cat4 = "1111110",		-dct_cat5, -dct_cat6 /* cat4 = "1111110",
	cat4 = "1111111" */		cat4 = "1111111" */
	};		};
	---- End code block ----------------------------------------		---- End code block ----------------------------------------
	While in general all DCT coefficients are decoded using the same		In general, all DCT coefficients are decoded using the same tree.
	tree, decoding of certain DCT coefficients may skip the first branch,		However, if the preceding coefficient is a DCT_0, decoding will skip
	whose preceding coefficient is a DCT_0. This makes use of the fact		the first branch since it is not possible for dct_eob to follow a
	that in any block last non zero coefficient before the end of the		DCT_0.
	block is not 0, therefore no dct_eob follows a DCT_0 coefficient in
	any block.
	The tokens dct_cat1 ... dct_cat6 specify ranges of unsigned values,		The tokens dct_cat1 ... dct_cat6 specify ranges of unsigned values,
	the value within the range being formed by adding an unsigned offset		the value within the range being formed by adding an unsigned offset
	(whose width is 1, 2, 3, 4, 5, or 11 bits, respectively) to the base		(whose width is 1, 2, 3, 4, 5, or 11 bits, respectively) to the base
	of the range, using the following algorithm and fixed probability		of the range, using the following algorithm and fixed probability
	tables.		tables.
	---- Begin code block --------------------------------------		---- Begin code block --------------------------------------
	uint DCTextra( bool_decoder *d, const Prob *p)		uint DCTextra( bool_decoder *d, const Prob *p)
	skipping to change at page 70, line 4 ¶		skipping to change at page 69, line 49 ¶
	The probability specification for the token tree (unlike that for the		The probability specification for the token tree (unlike that for the
	"extra bits" described above) is rather involved. It uses three		"extra bits" described above) is rather involved. It uses three
	pieces of context to index a large probability table, the contents of		pieces of context to index a large probability table, the contents of
	which may be incrementally modified in the frame header. The full		which may be incrementally modified in the frame header. The full
	(non-constant) probability table is laid out as follows.		(non-constant) probability table is laid out as follows.
	---- Begin code block --------------------------------------		---- Begin code block --------------------------------------
	Prob coef_probs [4] [8] [3] [num_dct_tokens-1];		Prob coef_probs [4] [8] [3] [num_dct_tokens-1];
	---- End code block ----------------------------------------
			---- End code block ----------------------------------------
	Working from the outside in, the outermost dimension is indexed by		Working from the outside in, the outermost dimension is indexed by
	the type of plane being decoded:		the type of plane being decoded:
	o 0 - Y beginning at coefficient 1 (i.e., Y after Y2)		o 0 - Y beginning at coefficient 1 (i.e., Y after Y2)
	o 1 - Y2		o 1 - Y2
	o 2 - U or V		o 2 - U or V
	o 3 - Y beginning at coefficient 0 (i.e., Y in the absence of Y2).		o 3 - Y beginning at coefficient 0 (i.e., Y in the absence of Y2).
	skipping to change at page 70, line 48 ¶		skipping to change at page 70, line 46 ¶
	is a fixed mapping of position to "band".		is a fixed mapping of position to "band".
	The third dimension is the trickiest. Roughly speaking, it measures		The third dimension is the trickiest. Roughly speaking, it measures
	the "local complexity" or extent to which nearby coefficients are		the "local complexity" or extent to which nearby coefficients are
	non-zero.		non-zero.
	For the first coefficient (DC, unless the block type is 0), we		For the first coefficient (DC, unless the block type is 0), we
	consider the (already encoded) blocks within the same plane (Y2, Y,		consider the (already encoded) blocks within the same plane (Y2, Y,
	U, or V) above and to the left of the current block. The context		U, or V) above and to the left of the current block. The context
	index is then the number (0, 1 or 2) of these blocks that had at		index is then the number (0, 1 or 2) of these blocks that had at
	least one non-zero coefficient in their residue record.		least one non-zero coefficient in their residue record. Specifically
			for Y2, because macroblocks above and to the left may or may not have
			a Y2 block, the block above is determined by the most recent
			macroblock in the same column that has a Y2 block, and the block to
			the left is determined by the most recent macroblock in the same row
			that has a Y2 block.
	Beyond the first coefficient, the context index is determined by the		Beyond the first coefficient, the context index is determined by the
	absolute value of the most recently decoded coefficient (necessarily		absolute value of the most recently decoded coefficient (necessarily
	within the current block) and is 0 if the last coefficient was a		within the current block) and is 0 if the last coefficient was a
	zero, 1 if it was plus or minus one, and 2 if its absolute value		zero, 1 if it was plus or minus one, and 2 if its absolute value
	exceeded one.		exceeded one.
	Note that the intuitive meaning of this measure changes as		Note that the intuitive meaning of this measure changes as
	coefficients are decoded. For example, prior to the first token, a		coefficients are decoded. For example, prior to the first token, a
	zero means that the neighbors are empty, suggesting that the current		zero means that the neighbors are empty, suggesting that the current
	skipping to change at page 141, line 4 ¶		skipping to change at page 140, line 19 ¶
	value corresponding to a certain used reference frame is updated		value corresponding to a certain used reference frame is updated
	(Section 9.4)		(Section 9.4)
	o delta_magnitude is the absolute value of the delta value		o delta_magnitude is the absolute value of the delta value
	o delta_sign is the sign of the delta value		o delta_sign is the sign of the delta value
	o mb_mode_delta_update_flag indicates if the adjustment delta value		o mb_mode_delta_update_flag indicates if the adjustment delta value
	corresponding to certain MB prediction mode is updated		corresponding to certain MB prediction mode is updated
	(Section 9.4)		(Section 9.4)
	+----------------------------+------+		+----------------------------+------+
	| quant_indices() | Type |		| quant_indices() | Type |
	+----------------------------+------+		+----------------------------+------+
	| y_ac_qi | L(7) |		| y_ac_qi | L(7) |
	| | |		| | |
	| y_dc_delta_present | L(1) |		| y_dc_delta_present | L(1) |
	| | |		| | |
	| if (y_dc_delta_present) { | |		| if (y_dc_delta_present) { | |
	| | |		| | |
	| y_dc_delta_magnitude | L(4) |		| y_dc_delta_magnitude | L(4) |
	| | |		| | |
	| y_dc_delta_sign | L(1) |		| y_dc_delta_sign | L(1) |
	| | |		| | |
	| } | |		| } | |
	| | |		| | |
			| y2_dc_delta_present | L(1) |
			| | |
	| if (y2_dc_delta_present) { | |		| if (y2_dc_delta_present) { | |
	| | |		| | |
	| y2_dc_delta_magnitude | L(4) |		| y2_dc_delta_magnitude | L(4) |
	| | |		| | |
	| y2_dc_delta_sign | L(1) |		| y2_dc_delta_sign | L(1) |
	| | |		| | |
	| } | |		| } | |
	| | |		| | |
			| y2_ac_delta_present | L(1) |
			| | |
	| if (y2_ac_delta_present) { | |		| if (y2_ac_delta_present) { | |
	| | |		| | |
	| y2_ac_delta_magnitude | L(4) |		| y2_ac_delta_magnitude | L(4) |
	| | |		| | |
	| y2_ac_delta_sign | L(1) |		| y2_ac_delta_sign | L(1) |
	| | |		| | |
	| } | |		| } | |
	| | |		| | |
			| uv_dc_delta_present | L(1) |
			| | |
	| if (uv_dc_delta_present) { | |		| if (uv_dc_delta_present) { | |
	| | |		| | |
	| uv_dc_delta_magnitude | L(4) |		| uv_dc_delta_magnitude | L(4) |
	| | |		| | |
	| uv_dc_delta_sign | L(1) |		| uv_dc_delta_sign | L(1) |
	| | |		| | |
	| } | |		| } | |
	| | |		| | |
			| uv_ac_delta_present | L(1) |
			| | |
	| if (uv_ac_delta_present) { | |		| if (uv_ac_delta_present) { | |
	| | |		| | |
	| uv_ac_delta_magnitude | L(4) |		| uv_ac_delta_magnitude | L(4) |
	| | |		| | |
	| uv_ac_delta_sign | L(1) |		| uv_ac_delta_sign | L(1) |
	| | |		| | |
	| } | |		| } | |
	+----------------------------+------+		+----------------------------+------+
	o y_ac_qi is the dequantization table index used for the luma AC		o y_ac_qi is the dequantization table index used for the luma AC
End of changes. 15 change blocks.
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