6225ad5c19
The code as written was wrong. In the spec, these fields are treated merely as plain integers in the range 0 to 4095. The only difference between L2 and L8 is that L2.ms_weight also accepts an additional value of -1, hence the extra sign bit. While it's likely that these are still shifted integers in disguise, since all real-world samples seem to use a value of 2048 here, the offset used in the code was wrong. In addition, because the l8.ms_weight struct member is unsigned, these wrong shifting semantics ended up overflowing the field, leading to undefined behavior when transcoding. Fortunately, the damage was relatively contained in practice, because it just corrupts the coding of this field, which is ignored in practice in all implementations I have seen.
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 means to alter decoded audio and video through a directed graph of connected 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.