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When the MagicYUV decoder builds Huffman tables from an array of code lengths, it proceeds as follows: First it copies the entries of the array of lengths into an array of HuffEntries (a struct which contains a length and a symbol field); it also sets the symbol field in descending order from nb_elem - 1 to 0, where nb_elem is the common number of elements of the length and HuffEntry arrays. Then the HuffEntry array is sorted lexicographically: a > b iff a.len > b.len or a.len == b.len and a.sym > b.sym. Afterwards the symbols of the so sorted array are inverted again (i.e. each symbol sym is replaced by nb_elem - sym). Yet inverting can easily be avoided altogether: Just modify the order so that smaller symbols correspond to bigger HuffEntries. This leads to the same permutation as the current code does and given that the two inversions just cancel each other out, the result is the same. Reviewed-by: Paul B Mahol <onemda@gmail.com> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@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.
- 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 and will be ignored.