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On2 Audio for Video Codec

2013-04-17T05:29:21Z

/* Huffman tables */

Revision as of 05:29, 17 April 2013		Current revision
Line 87:		Line 87:

	TODO		TODO
		+
		+	===== Scale differences table =====
		+
		+	Codes (-60..59):
		+
		+	0x6FFFF, 0xBFFF2, 0xBFFF3, 0xBFFF4, 0xBFFF5, 0xBFFF6,
		+	0xBFFF7, 0xBFFF8, 0xBFFF9, 0xBFFFA, 0xBFFFB, 0xBFFFC,
		+	0xBFFFD, 0xBFFFE, 0xBFFFF, 0xDF9A0, 0xDF9A1, 0xDF9A2,
		+	0xDF9A3, 0xDF9A4, 0xDF9A5, 0xDF9A6, 0xDF9A7, 0xDF9A8,
		+	0xDF9A9, 0x37FFE, 0x6FCDE, 0x6FFFA, 0x0BFF7, 0x0B7FF,
		+	0x0DF9F, 0x05FF8, 0x0B7FE, 0x05FF9, 0x06FCE, 0x05BFE,
		+	0x037FE, 0x02DFE, 0x00DFA, 0x00DFE, 0x017FC, 0x00DBE,
		+	0x00B7E, 0x005FE, 0x0037D, 0x002DE, 0x0017E, 0x0016C,
		+	0x000DE, 0x000BE, 0x0006C, 0x0005A, 0x0003E, 0x00034,
		+	0x0002C, 0x0001F, 0x0000E, 0x0000E, 0x00006, 0x00002,
		+	0x00000, 0x00004, 0x0000A, 0x0000C, 0x0001E, 0x0001E,
		+	0x0002E, 0x00035, 0x0003F, 0x0005E, 0x0006E, 0x000DA,
		+	0x0016D, 0x0016E, 0x001B6, 0x002FE, 0x0036E, 0x0037C,
		+	0x005BE, 0x006DE, 0x006FE, 0x00DBF, 0x00DFB, 0x016FE,
		+	0x017FD, 0x01BFE, 0x01BF2, 0x02FFE, 0x06FCC, 0x05FFE,
		+	0x05FFA, 0x06FFE, 0x0BFF6, 0x0BFFE, 0x0DF9E, 0x00DF8,
		+	0x0DFFE, 0x37FFC, 0x6FFFB, 0x5FFF8, 0xDF9AA, 0xDF9AB,
		+	0xDF9AC, 0xDF9AD, 0xDF9AE, 0xDF9AF, 0xDF9B0, 0xDF9B1,
		+	0xDF9B2, 0xDF9B3, 0x6FFFE, 0xDF9B4, 0xDF9B5, 0xDF9B6,
		+	0xDF9B7, 0xDF9B8, 0xDF9B9, 0xDF9BA, 0xDF9BB, 0xDF9BE,
		+
		+	Lengths:
		+
		+	20, 20, 20, 20, 20, 20,
		+	20, 20, 20, 20, 20, 20,
		+	20, 20, 20, 21, 21, 21,
		+	21, 21, 21, 21, 21, 21,
		+	21, 19, 20, 20, 16, 16,
		+	17, 15, 16, 15, 16, 15,
		+	15, 14, 13, 13, 13, 13,
		+	12, 11, 11, 10, 9, 9,
		+	9, 8, 8, 7, 7, 7,
		+	6, 5, 5, 4, 3, 3,
		+	2, 3, 4, 5, 5, 6,
		+	6, 7, 7, 7, 8, 9,
		+	9, 9, 10, 10, 11, 11,
		+	11, 12, 12, 13, 13, 13,
		+	13, 14, 14, 14, 16, 15,
		+	15, 16, 16, 16, 17, 13,
		+	17, 19, 20, 19, 21, 21,
		+	21, 21, 21, 21, 21, 21,
		+	21, 21, 20, 21, 21, 21,
		+	21, 21, 21, 21, 21, 21,

	[[Category:Audio Codecs]]		[[Category:Audio Codecs]]
	[[Category:Undiscovered Audio Codecs]]		[[Category:Undiscovered Audio Codecs]]

On2 Audio for Video Codec

2013-04-14T18:45:25Z

/* Window mode */ format as list

Revision as of 18:45, 14 April 2013		Current revision
Line 23:		Line 23:
	==== Window mode ====		==== Window mode ====

-	0 - ordinary long window	+	* 0 - ordinary long window
-	1 - long window with fading in delay	+	* 1 - long window with fading in delay
-	2 - long window with special windowing and delay handling	+	* 2 - long window with special windowing and delay handling
-	3 - eight short windows	+	* 3 - eight short windows
-	4-7 - long window with special windowing and delay handling	+	* 4-7 - long window with special windowing and delay handling

	==== Codebook description ====		==== Codebook description ====

On2 Audio for Video Codec

2013-04-14T07:23:36Z

Revision as of 07:23, 14 April 2013		Current revision
Line 1:		Line 1:
-	* Codec ID: 0x0501	+	* Codec ID: 0x0500, 0x0501
	* Company: [[On2]]		* Company: [[On2]]

	On2's Audio for Video codec (AVC) is a perceptual audio codec by On2, packaged in [[Microsoft Audio/Video Interleaved\|AVI]] files along with their video codecs.		On2's Audio for Video codec (AVC) is a perceptual audio codec by On2, packaged in [[Microsoft Audio/Video Interleaved\|AVI]] files along with their video codecs.
		+
		+	The codec seems to be MDCT-based with frame of 1024 samples.
		+
		+	Version <code>0x0500</code> coded only monaural sound with one chunk per audio frame, <code>0x0501</code> can be stereo and contain several chunks in a single frame (every chunk has 16-bit little-endian coded size before it).
		+
		+	=== Chunk format ===
		+
		+	enhanced mode flag (should be always zero)
		+	coding mode (3 bits)
		+	if (coding mode == 3) // short windows
		+	window grouping flags (7 bits)
		+	M/S present flag
		+	if (M/S present)
		+	M/S flags for each independent band
		+	codebook description
		+	scales
		+	coefficients
		+
		+	==== Window mode ====
		+
		+	0 - ordinary long window
		+	1 - long window with fading in delay
		+	2 - long window with special windowing and delay handling
		+	3 - eight short windows
		+	4-7 - long window with special windowing and delay handling
		+
		+	==== Codebook description ====
		+
		+	base = 0;
		+	nsect = 0;
		+	bps = long window ? 5 : 3;
		+	esc = (1 << bps) - 1;
		+	while (base < bands) {
		+	section[nsect].cb = get_bits(4);
		+	val = get_bits(bps);
		+	while (val == esc) {
		+	base += val;
		+	val = get_bits(bps);
		+	}
		+	base += val;
		+	section[nsect].end = base;
		+	nsect++;
		+	}
		+
		+	==== Scale description ====
		+
		+	Scales are read for all independent bands with non-zero coding. First scale is explicitly coded as 7-bit value, the following scales are coded as a difference to the previous scale with static Huffman code.
		+
		+	==== Coefficients ====
		+
		+	Coefficients are coded with 14 different static Huffman codesets. Codeset 0 is not coded, codesets 1-8 encode quadruplets of coefficients, codesets 9-15 code pairs of coefficients. Additionally, for codeset 15 values -16 and 16 are escape values. In case those escape values happen, real values are read as exp-Golomb plus three additional bits and the sign should be the same as the sign of escape value.
		+
		+	Unscaling is performed as <code>coeffs[i] = val * sqrt(val) * scale_tab[scale]</code>
		+
		+	=== Tables ===
		+
		+	==== Long window band ends ====
		+
		+	4, 8, 12, 16, 20, 24, 28, 32,
		+	36, 40, 48, 56, 64, 72, 80, 88,
		+	96, 108, 120, 132, 144, 156, 172, 188,
		+	204, 224, 244, 264, 288, 312, 340, 368,
		+	400, 432, 464, 496, 528, 560, 592, 624,
		+	656, 688, 720, 752, 784, 816, 848, 880,
		+	1024
		+
		+	==== Short window band ends ====
		+
		+	4, 8, 12, 16, 20, 24, 32, 40,
		+	48, 56, 68, 80, 108, 128
		+
		+	==== Scale table ====
		+
		+	For 0-19:
		+
		+	scale_tab[i] = ceil(exp(ln(10) / 10 * i) * 16) / 32
		+
		+	For 20-127:
		+
		+	scale_tab[i] = ceil(exp(ln(10) / 10 * i) * 0.5)
		+
		+	==== Huffman tables ====
		+
		+	TODO

	[[Category:Audio Codecs]]		[[Category:Audio Codecs]]
	[[Category:Undiscovered Audio Codecs]]		[[Category:Undiscovered Audio Codecs]]

FFmpeg bug testing

2013-04-12T15:32:21Z

Revision as of 15:32, 12 April 2013		Current revision
Line 30:		Line 30:
	in this case, msmpeg4dec.c , when encountering a dc overflow error, would return -1.		in this case, msmpeg4dec.c , when encountering a dc overflow error, would return -1.
	#try commenting out this in the source code, recompile, and test your changes to see if the picture changes for the better.		#try commenting out this in the source code, recompile, and test your changes to see if the picture changes for the better.
		+
		+	== testing for regressions ==
		+	#run make fate to check for any regressions in the code
		+	#test variety of samples relating to the code that has changed. make sure they decode visually and/or framemd5 identical.

	== results and conclusion ==		== results and conclusion ==
	there seems to be no way to switch asm optimizations on or off at runtime. its useful to have a seperate ffmpeg binary compiled with --disable-asm to test with.		there seems to be no way to switch asm optimizations on or off at runtime. its useful to have a seperate ffmpeg binary compiled with --disable-asm to test with.
		+
		+	ffmpeg should have some tests to make sure the various arch, asm and cpu optimizations of each codec are binary identical where possible.

FFmpeg Summer of Code 2013

2013-04-11T08:52:46Z

/* Introduction */ simplify note about project not accepted status

Revision as of 08:52, 11 April 2013		Current revision
Line 9:		Line 9:
	This is our ideas page for [http://www.google-melange.com/gsoc/homepage/google/gsoc2013 Google Summer of Code 2013].		This is our ideas page for [http://www.google-melange.com/gsoc/homepage/google/gsoc2013 Google Summer of Code 2013].

-	Note: '''FFmpeg has not been accepted this year''', so if you want to do any of the qualification tasks and projects, they are just for fun...	+	'''FFmpeg has not been accepted this year''', so if you want to do any of the qualification tasks and projects, they are just for fun.

	== Information for Students ==		== Information for Students ==

FFmpeg bug testing

2013-04-09T16:23:38Z

/* initial process */

New page

this document will try to explain the process used by bugtesters and developers to find and fix bugs in ffmpeg.

the process could be used in the future to automate bug testing. or find holes in our FATE coverage.

= example 1 - bug 2414 - wmv2 decoding artifacts =
*https://ffmpeg.org/trac/ffmpeg/ticket/2414
*sample: http://samples.ffmpeg.org/asf-wmv/wmv2decerror-short.asf

== initial process ==
#check if the official decoder/program handles the sample. it could be a broken file.
##mplayer -vc wmvdmo sample
#test sample with latest ffplay/ffmpeg.
##sometimes its already fixed.
##make sure its not an ffplay-only bug by also testing with ffmpeg.
#check with old version of ffmpeg to see if it is a regression bug.
#check if its a demuxer problem by testing with the ffmpeg/mplayer demuxer and official decoder.
##to test ffmpeg demuxer - mplayer -demuxer lavf -vc wmvdmo
##to test mplayer demuxer - mplayer -demuxer asf -vc wmvdmo

now that we know its not a demuxer problem, we can move onto debugging the decoder.

=== advanced codec debugging ===
#test if codec cpu optimizations are not binary identical to the c-version of the codec
##use ffmpeg -cpuflags 0 , ffmpeg has to be compiled with runtime cpu detection for this to work.
#test if codec asm version is not binary identical to the c-version of the codec
## recompile ffmpeg with --disable-asm

since codec also reports "dc overflow" error, check what the decoder does when it encounters this error. it is ffmpeg policy to report these errors, but also to continue decoding, in an effort to play as much of a file as possible.

in this case, msmpeg4dec.c , when encountering a dc overflow error, would return -1.
#try commenting out this in the source code, recompile, and test your changes to see if the picture changes for the better.

== results and conclusion ==
there seems to be no way to switch asm optimizations on or off at runtime. its useful to have a seperate ffmpeg binary compiled with --disable-asm to test with.

= required programs for bug testing =
bug testers should have the following installed:
#latest git ffmpeg binary with asm and cpu runtime detection enabled
#latest git ffmpeg binary with --disable-asm and cpu runtime detection
#older version ffmpeg binaries with and without asm
#official 3rd party players
##realplayer
##quicktime
##windows media player
#mplayer version with binary codec support
#vlc

FFmpeg Summer of Code 2013

2013-04-09T13:18:41Z

move and reword sentence about program status

Revision as of 13:18, 9 April 2013		Current revision
Line 8:		Line 8:

	This is our ideas page for [http://www.google-melange.com/gsoc/homepage/google/gsoc2013 Google Summer of Code 2013].		This is our ideas page for [http://www.google-melange.com/gsoc/homepage/google/gsoc2013 Google Summer of Code 2013].
		+
		+	Note: '''FFmpeg has not been accepted this year''', so if you want to do any of the qualification tasks and projects, they are just for fun...

	== Information for Students ==		== Information for Students ==

Libavfilter Shortcomings

2013-04-09T08:37:53Z

remove addresed stuff

Revision as of 08:37, 9 April 2013		Current revision
Line 1:		Line 1:
	Here a list of Libavfilter shortcomings that should be addressed:		Here a list of Libavfilter shortcomings that should be addressed:

-	* No error reporting in the callbacks
	* No support for reconfiguration		* No support for reconfiguration
-	* No way to provide a filter help with parameters
	* Avisynth-like features (script files, random access to source frames)		* Avisynth-like features (script files, random access to source frames)
	* higher-bit-depth support in most scenarios		* higher-bit-depth support in most scenarios