MultimediaWiki - User contributions [en]

Interesting Patches

2008-06-28T07:28:35Z

Mat:

This page tries to collect some useful patches that didn't make into SVN for some reason or another.

== native [[Zlib]] decoder by Mans Rullgard ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-July/032820.html

In the same thread, there are patches to use the native decoder in several FFmpeg decoders.

== [[WMV3]] encoder by Denis Fortin ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-June/031699.html

== [[H.263]] rtp patch ==
http://www.voxgratia.org/bin/ffmpeg-0.4.7.patch.zip, originally at http://www.salyens.com/downloads/index.html#ffmpeg-0.4.7, now removed.

== [[Apple RPZA]] encoder by Todd Kirby ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2005-June/001673.html

== 1 and 2 bit [[Apple QuickTime RLE|QTRLE]] decoder by Roberto Togni ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-January/022046.html

== Test Pattern Generator Demuxer by Nicholas George ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-October/036838.html

== Test Pattern Generator Demuxer by [[User:Angustia|Ramiro Ribeiro Polla]] ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-April/028226.html
Or
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/49447

== PES packetizer by Xiaohui Sun ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-September/034849.html

Part of the work of [[FFmpeg Summer Of Code#TS Muxer|Summer Of Code TS Muxer]]

== Imlib2script: a scriptable vhook by [[User:Wzrlpy|Víctor Paesa]] ==
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/52341

== vf_imlib2: a libavfilter filter by [[User:Wzrlpy|Víctor Paesa]] ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-soc/2007-December/002162.html

== File concatenation by Wolfram Gloger ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-July/032131.html

== "mem" file protocol by Lagrange Multiplier ==
The "mem" protocol simply uses RAM as a source for input multimedia data, akin to how the "file" and "pipe" protocols use filesystem files and pipes as sources.

http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-May/028489.html

== Presets/profiles for usual targets by Panagiotis Issaris ==
Allow to keep in a text file groups of command options, and apply them at once by specifying the target name.

Handy for iPod, PSP, or any other picky multimedia player that otherwise requires lengthy command lines.

http://article.gmane.org/gmane.comp.video.ffmpeg.devel/37244

== PiP (Picture in Picture): a vhook filter by Mihail Stoyanov ==
http://article.gmane.org/gmane.comp.video.ffmpeg.devel/38896

== [[MLP]]/[[TrueHD]] decoder by Ian Caulfield ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2008-January/040234.html

More details in the [[Small FFmpeg Tasks#Cleanup of MLP decoder|Small FFmpeg Tasks]] page.

== [[AMV]] encoder ==
http://code.google.com/p/amv-codec-tools/

See this post [http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-October/037356.html] to see what is missing to get it into SVN.

== [[Electronic Arts Formats]] demuxer/decoder by Peter Ross==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-October/036938.html
The format demuxer modifications and the EA video codecs have not yet been applied to FFmpeg.

== Experimental MSVC port by Ole André Vadla Ravnås ==
Code in the [http://bazaar-vcs.org bazaar] branch at http://people.collabora.co.uk/~oleavr/OABuild/bzr/ffmpeg/

Patch at http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2008-March/044463.html

== H264 encoder by Jori Liesenborgs & Panagiotis Issaris ==
http://research.edm.uhasselt.be/~h264/

== DTS/AC3 in wav autodetection ==
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/49812/focus=49909
Clean up this patch and also add detection of AC3 in wav, it is similar. Samples for both can be found here: http://www.sr.se/cgi-bin/mall/artikel.asp?ProgramID=2445&Artikel=739973

== [[Bink Audio]] decoder by Peter Ross ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2008-April/045346.html

Note: An updated patch is available from the [[User:Suxen drol|author]].

== G722 decoder by Chas Williams ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2008-June/048457.html

It is basically an adaptation to FFmpeg of the [http://www.soft-switch.org/ SirenDSP] decoder.

== [[Chinese AVS]] video encoder by [[User:StefanG|Stefan Gehrer]] ==
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-July/033286.html

== Lossless msmpeg4v3 to mpeg4 transcoder ==
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/17074

[[Category:FFmpeg]]

H.264

2007-05-28T19:32:56Z

Mat:

* FOURCCs: AVC1, DAVC, H264, X264, VSSH
* Matroska CodecID: V_MPEG4/ISO/AVC
* Technical Description: [http://akuvian.org/src/x264/ITU-T_H264.pdf.gz http://akuvian.org/src/x264/ITU-T_H264.pdf.gz]
* Draft Specs from 2003: [http://www.dspr.com/www/technology/JVT-G050.pdf http://www.dspr.com/www/technology/JVT-G050.pdf]
* Specs : http://www.itu.int/rec/T-REC-H.264/en
* Samples:
** AVC1: http://samples.mplayerhq.hu/V-codecs/AVC1/
** H264: http://samples.mplayerhq.hu/V-codecs/h264/
** VSSH: http://samples.mplayerhq.hu/V-codecs/VSSH/

MPEG-4 part 10 video, also known as AVC, or "Advanced Video Coding."

Here is a good picture comparing VC-1 and AVC.[http://home.wanadoo.nl/mvp35/S3_P3_Jeffrey_slide_10.png http://home.wanadoo.nl/mvp35/S3_P3_Jeffrey_slide_10.png]

[[Category:Video Codecs]]

H.261

2007-05-28T19:24:16Z

Mat:

* FourCCs: D261, H261, L261, M261, V261
* Organization: [[ITU]]
* Specs : http://www.itu.int/rec/T-REC-H.261-199303-I/en
* Samples: http://samples.mplayerhq.hu/V-codecs/h261/

H.261 is an early standard for video compression used in telecommunication applications.

These implementations are believed to be identical to the standard H.261:
* D261: Originated at [[DEC]]
* L261: Originated at [[LEAD Technologies]]
* M261: Originated at [[Microsoft]]
* V261: Originated at [[Lucent]]

[[Category:Video Codecs]]

H.263

2007-05-28T19:23:20Z

Mat:

* FourCCs: D263, H263, L263, M263, S263, U263, X263
* Organization: [[ITU]]
* Specs : http://www.itu.int/rec/T-REC-H.263-200501-I/en
* Samples:
** h263: http://samples.mplayerhq.hu/V-codecs/h263/
** U263: http://samples.mplayerhq.hu/V-codecs/U263/

H.263 is a video coding standard developed for telecommunications applications. Many other codecs are known to have borrowed concepts from the standard.

This site containts more information as well as source code: [http://www.h263l.com/ http://www.h263l.com].

These implementations are suspected to be identical to the standard H.263:
* D263: Originated at [[DEC]].
* L263: Originated at [[LEAD Technologies]]
* M263: Originated at [[Microsoft]]
* X263: Originated at [[Xirlink]]

[[Category:Video Codecs]]

H.261

2007-05-28T19:22:01Z

Mat:

* FourCCs: D261, H261, L261, M261, V261
* Organization: [[ITU]]
* Draft Specs : http://www.itu.int/rec/T-REC-H.261-199012-S/en
* Samples: http://samples.mplayerhq.hu/V-codecs/h261/

H.261 is an early standard for video compression used in telecommunication applications.

These implementations are believed to be identical to the standard H.261:
* D261: Originated at [[DEC]]
* L261: Originated at [[LEAD Technologies]]
* M261: Originated at [[Microsoft]]
* V261: Originated at [[Lucent]]

[[Category:Video Codecs]]

Valgrind

2007-04-21T20:17:10Z

Mat:

[http://valgrind.org/ Valgrind] is an suite of tools for debugging and profiling Linux programs.

The Callgrind tools allow to profile a program.

When it is used with "--dump-instr=yes --trace-jump=yes" and the result is displayed with [http://kcachegrind.sourceforge.net/cgi-bin/show.cgi/KcacheGrindIndex], you could see :
- function call tracing
- executed calltree graphing
- jmp tracing and graphing

== Exemple ==

$ valgrind --tool=callgrind --dump-instr=yes --trace-jump=yes ffplay
$ kcachegrind callgrind.$pid

[[Category: RE Tools]]

Reverse Engineering Tools

2007-04-21T20:05:12Z

Mat: /* Linux/Unix */

Here is a list of free (mostly as in beer) tools that can be used to aid Reverse Engineering.
The list is divided into software that can be run under Win32 only, Win32/Wine and Linux/Unix.

==Disassemblers==
=== Win32/Wine ===
* [[IDA Pro]]

=== Win32 only ===
* [[OllyDbg]]

=== Linux/Unix ===
* [[objdump]]
* [[hte|HT Editor]]
* [[Boomerang]]
* [[Rewind]]
* [[strings]]
* [[valgrind]]

=== Java ===
* [http://www.multimedia.cx/pre/re-retroguard.html Java De-obfuscation]
* [http://www.kpdus.com/jad.html jad - Java Disassembler]

=== Cross Platform ===
* [[Sang Cho's Win32 Disassembler]]
* [http://rr0d.droids-corp.org/ Rasta Ring 0 Debugger (RR0D)]

== Network Analysis ==
* [[WireShark]]
* [[Internet Junkbuster]]

== Other ==
* [[Hachoir]]: File parser framework written in Python

[[Category:RE Tools]]

Reverse Engineering Tools

2007-04-21T20:05:01Z

Mat: /* Linux/Unix */

Here is a list of free (mostly as in beer) tools that can be used to aid Reverse Engineering.
The list is divided into software that can be run under Win32 only, Win32/Wine and Linux/Unix.

==Disassemblers==
=== Win32/Wine ===
* [[IDA Pro]]

=== Win32 only ===
* [[OllyDbg]]

=== Linux/Unix ===
* [[objdump]]
* [[hte|HT Editor]]
* [[Boomerang]]
* [[Rewind]]
* [[strings]]
* [[valgring]]

=== Java ===
* [http://www.multimedia.cx/pre/re-retroguard.html Java De-obfuscation]
* [http://www.kpdus.com/jad.html jad - Java Disassembler]

=== Cross Platform ===
* [[Sang Cho's Win32 Disassembler]]
* [http://rr0d.droids-corp.org/ Rasta Ring 0 Debugger (RR0D)]

== Network Analysis ==
* [[WireShark]]
* [[Internet Junkbuster]]

== Other ==
* [[Hachoir]]: File parser framework written in Python

[[Category:RE Tools]]

Apple Lossless Audio Coding

2006-06-04T18:01:00Z

Mat: /* Frame Header */

* FOURCCS: alac
* Company: [[Apple]]
* Technical Description: http://craz.net/programs/itunes/alac.html
* Samples: http://mplayerhq.hu/MPlayer/samples/A-codecs/lossless/ (luckynight.m4a)

Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an [[Apple QuickTime|MP4]] container, as a private extension since it is not part of the MPEG-4 standard.

=== Extradata ===

{| border="1"
! Syntax !! Number of bits !! Semantics
|-
|atom size || 32 || (0x24), big-endian
|-
|tag || 32 || 'alac'
|-
|??? || 32 || zero ?
|-
|max sample per frame || 32 ||
|-
|??? || 8 || zero ?
|-
|sample size || 8 ||
|-
|rice history mult || 8 ||
|-
|rice initial history || 8 ||
|-
|rice kmodifier || 8 ||
|-
|channels || 8 || ?
|-
|??? || 16 ||
|-
|max coded frame size || 32 ||
|-
|bitrate || 32 || ?
|-
|samplerate || 32 ||
|}

=== Frame Header ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| channels || 3 || Number of channel -1 (Should be the same than in extradata ???)
|-
| ??? || 4 || ??? (seem to be always 0)
|-
| ??? || 12 || ??? (seem to be always 0)
|-
| hasoutputsamples || 1 || the number of samples is stored in the header
|-
| wasted_bytes || 2 || unknow (same as flac ???)
|-
| isverbatim || 1 || if 1, the data is not compressed
|-
| if (hasoutputsamples) { || ||
|-
| outputsamples || 32 || number of samples (sometimes the value is wrong [1])
|-
| } || ||
|}

[1] http://www1.mplayerhq.hu/MPlayer/samples/A-codecs/lossless/luckynight.m4a need + 32 and http://www1.mplayerhq.hu/MPlayer/samples/A-codecs/lossless/ALAC/old_midi_stuff.m4a + 112

=== Verbatim frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| data || sample_size * outputsamples * channels || Unencoded subblock
|}

=== Compressed frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| interlacing_shift || 8 || should be 0 if no channel interlacing.
|-
| interlacing_leftweight || 8 ||
|-
| for each channel {
|-
| prediction_type || 4 || should be 0
|-
| prediction_quantitization || 4 ||
|-
| ricemodifier || 3 ||
|-
| predictor_coef_num || 5 ||
|-
| predictor_coef_table || 16 * predictor_coef_num ||
|-
| }
|-
| for each channel {
|-
| compressed data || || modfied Rice coding and Adaptive FIR filter
|-
| }
|}

Channel Interlacing

It is a mid/side stereo with weight.
channel 0 is the mid(average) channel, channel 1 is the side(difference) channel.

:''right = mid - ((difference * interlacing_leftweight) >> interlacing_shift)''
:''left = right + difference''

It seems we have interlacing_leftweight == interlacing_shift in most of the samples

=== Frame Footer ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| EOF || 3 || should be always 7
|}

[[Category:Lossless Audio Codecs]]
[[Category:Audio Codecs]]

Apple Lossless Audio Coding

2006-06-04T18:00:24Z

Mat: /* Frame Header */

* FOURCCS: alac
* Company: [[Apple]]
* Technical Description: http://craz.net/programs/itunes/alac.html
* Samples: http://mplayerhq.hu/MPlayer/samples/A-codecs/lossless/ (luckynight.m4a)

Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an [[Apple QuickTime|MP4]] container, as a private extension since it is not part of the MPEG-4 standard.

=== Extradata ===

{| border="1"
! Syntax !! Number of bits !! Semantics
|-
|atom size || 32 || (0x24), big-endian
|-
|tag || 32 || 'alac'
|-
|??? || 32 || zero ?
|-
|max sample per frame || 32 ||
|-
|??? || 8 || zero ?
|-
|sample size || 8 ||
|-
|rice history mult || 8 ||
|-
|rice initial history || 8 ||
|-
|rice kmodifier || 8 ||
|-
|channels || 8 || ?
|-
|??? || 16 ||
|-
|max coded frame size || 32 ||
|-
|bitrate || 32 || ?
|-
|samplerate || 32 ||
|}

=== Frame Header ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| channels || 3 || Number of channel -1 (Should be the same than in extradata ???)
|-
| ??? || 4 || ??? (seem to be always 0)
|-
| ??? || 12 || ??? (seem to be always 0)
|-
| hasoutputsamples || 1 || the number of samples is stored in the header
|-
| wasted_bytes || 2 || unknow (same as flac ???)
|-
| isverbatim || 1 || if 1, the data is not compressed
|-
| if (hassize) { || ||
|-
| outputsamples || 32 || number of samples (sometimes the value is wrong [1])
|-
| } || ||
|}

[1] http://www1.mplayerhq.hu/MPlayer/samples/A-codecs/lossless/luckynight.m4a need + 32 and http://www1.mplayerhq.hu/MPlayer/samples/A-codecs/lossless/ALAC/old_midi_stuff.m4a + 112

=== Verbatim frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| data || sample_size * outputsamples * channels || Unencoded subblock
|}

=== Compressed frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| interlacing_shift || 8 || should be 0 if no channel interlacing.
|-
| interlacing_leftweight || 8 ||
|-
| for each channel {
|-
| prediction_type || 4 || should be 0
|-
| prediction_quantitization || 4 ||
|-
| ricemodifier || 3 ||
|-
| predictor_coef_num || 5 ||
|-
| predictor_coef_table || 16 * predictor_coef_num ||
|-
| }
|-
| for each channel {
|-
| compressed data || || modfied Rice coding and Adaptive FIR filter
|-
| }
|}

Channel Interlacing

It is a mid/side stereo with weight.
channel 0 is the mid(average) channel, channel 1 is the side(difference) channel.

:''right = mid - ((difference * interlacing_leftweight) >> interlacing_shift)''
:''left = right + difference''

It seems we have interlacing_leftweight == interlacing_shift in most of the samples

=== Frame Footer ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| EOF || 3 || should be always 7
|}

[[Category:Lossless Audio Codecs]]
[[Category:Audio Codecs]]

Apple Lossless Audio Coding

2006-06-04T17:52:57Z

Mat: /* Frame Header */

* FOURCCS: alac
* Company: [[Apple]]
* Technical Description: http://craz.net/programs/itunes/alac.html
* Samples: http://mplayerhq.hu/MPlayer/samples/A-codecs/lossless/ (luckynight.m4a)

Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an [[Apple QuickTime|MP4]] container, as a private extension since it is not part of the MPEG-4 standard.

=== Extradata ===

{| border="1"
! Syntax !! Number of bits !! Semantics
|-
|atom size || 32 || (0x24), big-endian
|-
|tag || 32 || 'alac'
|-
|??? || 32 || zero ?
|-
|max sample per frame || 32 ||
|-
|??? || 8 || zero ?
|-
|sample size || 8 ||
|-
|rice history mult || 8 ||
|-
|rice initial history || 8 ||
|-
|rice kmodifier || 8 ||
|-
|channels || 8 || ?
|-
|??? || 16 ||
|-
|max coded frame size || 32 ||
|-
|bitrate || 32 || ?
|-
|samplerate || 32 ||
|}

=== Frame Header ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| channels || 3 || Number of channel -1 (Should be the same than in extradata ???)
|-
| ??? || 4 || ???
|-
| ??? || 12 || ???
|-
| hasoutputsamples || 1 || the number of samples is stored in the header
|-
| wasted_bytes || 2 || unknow (same as flac ???)
|-
| isverbatim || 1 || if 1, the data is not compressed
|-
| if (hassize) { || ||
|-
| outputsamples || 32 || number of samples (sometimes the value is wrong [1])
|-
| } || ||
|}

[1] http://www1.mplayerhq.hu/MPlayer/samples/A-codecs/lossless/luckynight.m4a need + 32 and http://www1.mplayerhq.hu/MPlayer/samples/A-codecs/lossless/ALAC/old_midi_stuff.m4a + 112

=== Verbatim frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| data || sample_size * outputsamples * channels || Unencoded subblock
|}

=== Compressed frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| interlacing_shift || 8 || should be 0 if no channel interlacing.
|-
| interlacing_leftweight || 8 ||
|-
| for each channel {
|-
| prediction_type || 4 || should be 0
|-
| prediction_quantitization || 4 ||
|-
| ricemodifier || 3 ||
|-
| predictor_coef_num || 5 ||
|-
| predictor_coef_table || 16 * predictor_coef_num ||
|-
| }
|-
| for each channel {
|-
| compressed data || || modfied Rice coding and Adaptive FIR filter
|-
| }
|}

Channel Interlacing

It is a mid/side stereo with weight.
channel 0 is the mid(average) channel, channel 1 is the side(difference) channel.

:''right = mid - ((difference * interlacing_leftweight) >> interlacing_shift)''
:''left = right + difference''

It seems we have interlacing_leftweight == interlacing_shift in most of the samples

=== Frame Footer ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| EOF || 3 || should be always 7
|}

[[Category:Lossless Audio Codecs]]
[[Category:Audio Codecs]]

Apple Lossless Audio Coding

2006-05-26T16:50:21Z

Mat:

* FOURCCS: alac
* Company: [[Apple]]
* Technical Description: http://craz.net/programs/itunes/alac.html
* Samples: http://mplayerhq.hu/MPlayer/samples/A-codecs/lossless/ (luckynight.m4a)

Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an [[Apple QuickTime|MP4]] container, as a private extension since it is not part of the MPEG-4 standard.

=== Extradata ===

{| border="1"
! Syntax !! Number of bits !! Semantics
|-
|atom size || 32 || (0x24), big-endian
|-
|tag || 32 || 'alac'
|-
|??? || 32 || zero ?
|-
|max sample per frame || 32 ||
|-
|??? || 8 || zero ?
|-
|sample size || 8 ||
|-
|rice history mult || 8 ||
|-
|rice initial history || 8 ||
|-
|rice kmodifier || 8 ||
|-
|channels || 8 || ?
|-
|??? || 16 ||
|-
|max coded frame size || 32 ||
|-
|bitrate || 32 || ?
|-
|samplerate || 32 ||
|}

=== Frame Header ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| channels || 3 || Number of channel -1 (Should be the same than in extradata ???)
|-
| ??? || 4 || ???
|-
| ??? || 12 || ???
|-
| hasoutputsamples || 1 || the number of samples is stored in the header
|-
| wasted_bytes || 2 || unknow (same as flac ???)
|-
| isverbatim || 1 || if 1, the data is not compressed
|-
| if (hassize) { || ||
|-
| outputsamples || 32 || number of samples
|-
| } || ||
|}

=== Verbatim frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| data || sample_size * outputsamples * channels || Unencoded subblock
|}

=== Compressed frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| interlacing_shift || 8 || should be 0 if no channel interlacing.
|-
| interlacing_leftweight || 8 ||
|-
| for each channel {
|-
| prediction_type || 4 || should be 0
|-
| prediction_quantitization || 4 ||
|-
| ricemodifier || 3 ||
|-
| predictor_coef_num || 5 ||
|-
| predictor_coef_table || 16 * predictor_coef_num ||
|-
| }
|-
| for each channel {
|-
| compressed data || || modfied Rice coding and Adaptive FIR filter
|-
| }
|}

Channel Interlacing

It is a mid/side stereo with weight.
channel 0 is the mid(average) channel, channel 1 is the side(difference) channel.

:''right = mid - ((difference * interlacing_leftweight) >> interlacing_shift)''
:''left = right + difference''

It seems we have interlacing_leftweight == interlacing_shift in most of the samples

=== Frame Footer ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| EOF || 3 || should be always 7
|}

[[Category:Lossless Audio Codecs]]
[[Category:Audio Codecs]]

Apple Lossless Audio Coding

2006-05-25T21:18:35Z

Mat:

* FOURCCS: alac
* Company: [[Apple]]
* Technical Description: [http://craz.net/programs/itunes/alac.html http://craz.net/programs/itunes/alac.html]

Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an [[Apple QuickTime|MP4]] container, as a private extension since it is not part of the MPEG-4 standard.

=== Extradata ===

{| border="1"
! Syntax !! Number of bits !! Semantics
|-
|atom size || 32 || (0x24), big-endian
|-
|tag || 32 || 'alac'
|-
|??? || 32 || zero ?
|-
|max sample per frame || 32 ||
|-
|??? || 8 || zero ?
|-
|sample size || 8 ||
|-
|rice history mult || 8 ||
|-
|rice initial history || 8 ||
|-
|rice kmodifier || 8 ||
|-
|channels || 8 || ?
|-
|??? || 16 ||
|-
|max coded frame size || 32 ||
|-
|bitrate || 32 || ?
|-
|samplerate || 32 ||
|}

=== Frame Header ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| channels || 3 || Number of channel -1 (Should be the same than in extradata ???)
|-
| ??? || 4 || ???
|-
| ??? || 12 || ???
|-
| hasoutputsamples || 1 || the number of samples is stored in the header
|-
| wasted_bytes || 2 || unknow (same as flac ???)
|-
| isverbatim || 1 || if 1, the data is not compressed
|-
| if (hassize) { || ||
|-
| outputsamples || 32 || number of samples
|-
| } || ||
|}

=== Verbatim frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| data || sample_size * outputsamples * channels || Unencoded subblock
|}

=== Compressed frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| interlacing_shift || 8 || should be 0 if no channel interlacing.
|-
| interlacing_leftweight || 8 ||
|-
| for each channel {
|-
| prediction_type || 4 || should be 0
|-
| prediction_quantitization || 4 ||
|-
| ricemodifier || 3 ||
|-
| predictor_coef_num || 5 ||
|-
| predictor_coef_table || 16 * predictor_coef_num ||
|-
| }
|-
| for each channel {
|-
| compressed data || || modfied Rice coding and Adaptive FIR filter
|-
| }
|}

Channel Interlacing

It is a mid/side stereo with weight.
channel 0 is the mid(average) channel, channel 1 is the side(difference) channel.

:''right = mid - ((difference * interlacing_leftweight) >> interlacing_shift)''
:''left = right + difference''

[[Category:Lossless Audio Codecs]]
[[Category:Audio Codecs]]

Apple Lossless Audio Coding

2006-05-25T21:09:40Z

Mat: /* Compressed frame */

* FOURCCS: alac
* Company: [[Apple]]
* Technical Description: [http://craz.net/programs/itunes/alac.html http://craz.net/programs/itunes/alac.html]

Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an [[Apple QuickTime|MP4]] container, as a private extension since it is not part of the MPEG-4 standard.

=== Frame Header ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| channels || 3 || Number of channel -1 (Should be the same than in extradata ???)
|-
| ??? || 4 || ???
|-
| ??? || 12 || ???
|-
| hasoutputsamples || 1 || the number of samples is stored in the header
|-
| wasted_bytes || 2 || unknow (same as flac ???)
|-
| isverbatim || 1 || if 1, the data is not compressed
|-
| if (hassize) { || ||
|-
| outputsamples || 32 || number of samples
|-
| } || ||
|}

=== Verbatim frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| data || sample_size * outputsamples * channels || Unencoded subblock
|}

=== Compressed frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| interlacing_shift || 8 || should be 0 if no channel interlacing.
|-
| interlacing_leftweight || 8 ||
|-
| for each channel {
|-
| prediction_type || 4 || should be 0
|-
| prediction_quantitization || 4 ||
|-
| ricemodifier || 3 ||
|-
| predictor_coef_num || 5 ||
|-
| predictor_coef_table || 16 * predictor_coef_num ||
|-
| }
|-
| for each channel {
|-
| compressed data || || modfied Rice coding and Adaptive FIR filter
|-
| }
|}

Channel Interlacing

It is a mid/side stereo with weight.
channel 0 is the mid(average) channel, channel 1 is the side(difference) channel.

:''right = mid - ((difference * interlacing_leftweight) >> interlacing_shift)''
:''left = right + difference''

[[Category:Lossless Audio Codecs]]
[[Category:Audio Codecs]]

Apple Lossless Audio Coding

2006-05-14T17:43:37Z

Mat:

* FOURCCS: alac
* Company: [[Apple]]
* Technical Description: [http://craz.net/programs/itunes/alac.html http://craz.net/programs/itunes/alac.html]

Lossless audio coding using linear prediction with Golomb-Rice coding of the difference. Similar to FLAC, although the bitstreams are not compatible. Usually stored in an [[Apple QuickTime|MP4]] container, as a private extension since it is not part of the MPEG-4 standard.

=== Frame Header ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| channels || 3 || Number of channel -1 (Should be the same than in extradata ???)
|-
| ??? || 4 || ???
|-
| ??? || 12 || ???
|-
| hasoutputsamples || 1 || the number of samples is stored in the header
|-
| wasted_bytes || 2 || unknow (same as flac ???)
|-
| isverbatim || 1 || if 1, the data is not compressed
|-
| if (hassize) { || ||
|-
| outputsamples || 32 || number of samples
|-
| } || ||
|}

=== Verbatim frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| data || sample_size * outputsamples * channels || Unencoded subblock
|}

=== Compressed frame ===
{| border="1"
! Syntax !! Number of bits !! Semantics
|-
| interlacing_shift || 8 || 0 if no channel interlacing.
|-
| interlacing_leftweight || 8 ||
|-
| for each channel {
|-
| prediction_type || 4 || should be 0
|-
| prediction_quantitization || 4 ||
|-
| ricemodifier || 3 ||
|-
| predictor_coef_num || 5 ||
|-
| predictor_coef_table || 16 * predictor_coef_num ||
|-
| bastardized_rice_decompressed data || ||
|-
| }
|}

Channel Interlacing

It is a mid/side stereo with weight.
channel 0 is the mid(average) channel, channel 1 is the side(difference) channel.

:''right = mid - ((difference * interlacing_leftweight) >> interlacing_shift)''
:''left = right + difference''

[[Category:Lossless Audio Codecs]]
[[Category:Audio Codecs]]

Apple Lossless Audio Coding

2006-05-14T17:14:48Z

Mat:

IDA Pro

2006-03-31T20:38:58Z

Mat: update demo link + a link with wingraph32 source code

* Website: [http://www.datarescue.com/idabase/index.htm http://www.datarescue.com/idabase/index.htm]
* Demo version: [http://www.datarescue.com/idabase/idadown.htm http://www.datarescue.com/idabase/idadown.htm]
* Freeware version: [http://www.datarescue.be/idafreeware/freeida43.exe http://www.datarescue.be/idafreeware/freeida43.exe]
* Wingraph32 GPL source code: [http://www.datarescue.com/freefiles/wingraph32_src.zip http://www.datarescue.com/freefiles/wingraph32_src.zip]

IDA Pro is a disassembler and debugger with a lot of features that is very useful for reverse engineering.

It is proprietary software that runs on Windows and Linux; there is a zero-cost evaluation version.

== Boosting the freeware version ==
The freeware version of IDA Pro is an invaluable tool. One important function is the ability to produce different flow graphs
from the disassembly. Sometimes these graphs can be quite messy and needs to be processed. The version of wingraph32.exe that
is included with the freeware version of IDA Pro can't save the generated graphs. Just replace it with a version from a demo
version of IDA Pro and the save option will be availible. Saved graphs will have a .gdl suffix.

== Recovering the function prototypes from the disassembly ==
Well it's not really possible but a good hint is possible without much work. First load the binary you want to analyse. IDA Pro
will process the file for some time. If you start browsing around you will see that IDA Pro can make a good guess on how many
arguments a function have. That is one thing that can be extracted. The other is if a function returns something or not. The x86 C ABI
declares that the return type if any has to be left in the eax register. So if the eax register is used after a call the function
that was called returned something. The following not so nice perl script can process the asm file that can be produced from IDA Pro
with Produce->ASM-File (Alt+F10).

#!/usr/bin/perl
#Argument parser

if (@ARGV){
print "@ARGV\n";
if ($ARGV[0] eq "-f"){
$FILE1 = $ARGV[1];
$FILE2 = $ARGV[2];
$filter = 1;
}
}
else{
print "Usage:\n";
print "./argumentcounter.pl [command] file.asm output.txt\n";
print "-f dummy command\n";
exit;
}

#File IO
open(OUTFILE, ">$FILE2") or die "File problem\n";
@indata = `cat $FILE1`;

$fn = 0; #amount of founctions
$functions[$fn] = "";
$arguments[$fn] = 0;
$f_start = 0;
$links= 0;
foreach $rad (@indata)
{
$rowcounter++;

if ($rad =~ m/ proc near/) {
$functions[$fn] = $`;
$fn++;
$f_start = 1;
$arguments[$fn] = 0;
#print STDOUT "$`\n";
}
if ($f_start == 1) {
$radsubstring = (substr $rad,0,3);
if ($radsubstring eq "arg") {
$arguments[$fn]++;
}
}
if ($rad =~ m/ endp/) {
$f_start = 0;
}

#return type detector
if ($rad =~ m/call\t/) {
$retfunction = $';
$retfunction =~ m/\n/;
$retfunction = $`;
chop($retfunction);
$rowcounter = 0;
$callcheck = 1;
}
if (($callcheck) && ($rowcounter>0)) {

@tmpsplit=split /\t/,$rad;
chomp($tmpsplit[0]);
chomp($tmpsplit[1]);
chomp($tmpsplit[2]);
chomp($tmpsplit[3]);
$instruction = $tmpsplit[2];
$arguments = $tmpsplit[3];
chop($arguments);
if ($arguments =~ m/, /) {
@argum=split /, /,$arguments;
}
#chomp($argum[0]);
#chomp($instruction);
if ($argum[0] eq "eax") {
$callcheck = 0;
}
if ($argum[1] eq "eax") {
$callcheck = 0;
}

#check source operand if it is eax
if (($argum[1] eq "eax") && ($instruction ne "xor")) {
$callcheck = 0;
$nonvoid{$retfunction} = $nonvoid{$retfunction} +1;
#print STDOUT "$retfunction returns nonvoid\n";
}
if (($argum[0] eq "eax") && ($argum[1] ne "eax")){
$callcheck = 0;
$void{$retfunction} = $void{$retfunction} +1;
#print STDOUT "$retfunction returns void\n";
}
if ($instruction =~ /retn/) {
#stop searching when the current function returns
$callcheck = 0;
$void{$retfunction} = $void{$retfunction} +1;
#print STDOUT "$retfunction returns void\n";
}
if ($rowcounter > 10) {
$callcheck = 0;
}
$argum[0] = "";
$argum[1] = "";
}
}

for ($i=0 ; $i < $fn ; $i++){
#returntype handling
$returntype = "unknown";
if ($void{$functions[$i]} > 0) {
$returntype = "void";
}
if ($nonvoid{$functions[$i]} > 0) {
$returntype = "int";
}
if (($void{$functions[$i]} > 0) && ($nonvoid{$functions[$i]} > 0)){
$returntype = "void $void{$functions[$i]} - $nonvoid{$functions[$i]} int";
}
print STDOUT "$returntype $functions[$i] $arguments[$i]\n";
}

[[Category:RE Tools]]