fc28cb4ed5
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@20901 a1c6a512-1295-4272-9138-f99709370657
58 lines
2.1 KiB
Text
58 lines
2.1 KiB
Text
Library: libcook
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Imported by : Mohamed Tarek
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These files comprise a rm parser and a cook decoder based on the decoder
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from ffmpeg.
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LICENSING INFORMATION
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ffmpeg is licensed under the Lesser GNU General Public License and the
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file cook.c is Copyright 2003 Sascha Sommer and 2005 Benjamin Larsson.
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IMPORT DETAILS
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The decoder is based on ffmpeg-svn r18079.
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The file libavcodec/cook.c was modified to remove all ffmpeg-specific
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code and to use the current rm parser.
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In initializing random_state in COOKContext, ffmpeg used a random_seed()
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function that was weird in the way it gets the random number. So it was
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decided to not use this function at all,and the value was initialized to 1,
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because according to Benjamin Larsson random_seed() could just be
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replaced by any value.
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The current files contain lots of code which is either not needed by
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the decoder or totally disabled (#if 0 .. #endif) to enable
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compiling. This was during the isolation of the decoder from ffmpeg,
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the intention was to take as few files as possible to be able to
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compile cook.c and the related files outside ffmpeg.
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The decoder still uses floating point and relies on dynamic allocations
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in some parts of it. It's still not ready to be ported to rockbox.
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CONVERSION TO FIXED-POINT
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A patch from ffmpeg's mailing list was used to convert the decoder to
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use fixed-point arithmetic. The patch was done by Ian Braithwaite, and
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discussed here :
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http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/46024
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The patch is a bit dated (2007) so the modifications to cook.c had to
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be done manually. The patch was also applied to cookdata.h and was
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used to create cookdata_fixpoint.h, cook_fixpoint.h and
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cook_fixp_mdct.h.
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The patch used a cook_random() function for noise filling. this was
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dropped and av_lfg_get() was used instead for consistency.
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Note : Only parts of the patch were committed to ffmpeg's repository.
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TESTING
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The test program should compile in any Unix-like environment using the
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command "make -f Makefile.test".
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Running "./cooktest file.rm" will decode the audio data to a WAV file
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called "output.wav" in the current directory.
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