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ff_huff_build_tree uses qsort underneath. AV_QSORT is substantially faster due to the inlining of the comparison callback. Furthermore, this code is reasonably performance critical, since in e.g the fraps codec, ff_huff_build_tree is called on every frame. This routine is also called in vp6 on every frame in some circumstances. Sample benchmark (x86-64, Haswell, GNU/Linux), vp6 from FATE: vp6 (old): 78930 decicycles in qsort, 1 runs, 0 skips 45330 decicycles in qsort, 2 runs, 0 skips 27825 decicycles in qsort, 4 runs, 0 skips 17471 decicycles in qsort, 8 runs, 0 skips 12296 decicycles in qsort, 16 runs, 0 skips 9554 decicycles in qsort, 32 runs, 0 skips 8404 decicycles in qsort, 64 runs, 0 skips 7405 decicycles in qsort, 128 runs, 0 skips 6740 decicycles in qsort, 256 runs, 0 skips 7540 decicycles in qsort, 512 runs, 0 skips 9498 decicycles in qsort, 1024 runs, 0 skips 9938 decicycles in qsort, 2048 runs, 0 skips 8043 decicycles in qsort, 4095 runs, 1 skips vp6 (new): 15880 decicycles in qsort, 1 runs, 0 skips 10730 decicycles in qsort, 2 runs, 0 skips 10155 decicycles in qsort, 4 runs, 0 skips 7805 decicycles in qsort, 8 runs, 0 skips 6883 decicycles in qsort, 16 runs, 0 skips 6305 decicycles in qsort, 32 runs, 0 skips 5854 decicycles in qsort, 64 runs, 0 skips 5152 decicycles in qsort, 128 runs, 0 skips 4452 decicycles in qsort, 256 runs, 0 skips 4161 decicycles in qsort, 511 runs, 1 skips 4081 decicycles in qsort, 1023 runs, 1 skips 4072 decicycles in qsort, 2047 runs, 1 skips 4004 decicycles in qsort, 4095 runs, 1 skips Reviewed-by: Timothy Gu <timothygu99@gmail.com> Reviewed-by: Michael Niedermayer <michael@niedermayer.cc> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
FFmpeg README
FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.
Libraries
libavcodecprovides implementation of a wider range of codecs.libavformatimplements streaming protocols, container formats and basic I/O access.libavutilincludes hashers, decompressors and miscellaneous utility functions.libavfilterprovides a mean to alter decoded Audio and Video through chain of filters.libavdeviceprovides an abstraction to access capture and playback devices.libswresampleimplements audio mixing and resampling routines.libswscaleimplements color conversion and scaling routines.
Tools
- ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
- ffplay is a minimalistic multimedia player.
- ffprobe is a simple analysis tool to inspect multimedia content.
- ffserver is a multimedia streaming server for live broadcasts.
- Additional small tools such as
aviocat,ismindexandqt-faststart.
Documentation
The offline documentation is available in the doc/ directory.
The online documentation is available in the main website and in the wiki.
Examples
Coding examples are available in the doc/examples directory.
License
FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.
Contributing
Patches should be submitted to the ffmpeg-devel mailing list using
git format-patch or git send-email. Github pull requests should be
avoided because they are not part of our review process. Few developers
follow pull requests so they will likely be ignored.