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The MPEG-1/2 decoder uses avpriv_find_start_code to search for start codes and worked with the resulting start code before checking that it is really a start code of a slice. In particular, if the picture is so big that a slice_vertical_position_extension is present, it added the slice_vertical_position_extension as if it had a slice. Then a left shift is performed, without making sure that the value to be shifted is nonnegative. Afterwards the end result is checked, but even if a start code of a non-slice has been found, it might pass these checks: If slice_vertical_position_extension is present a start code < SLICE_MIN_START_CODE can lead to a macroblock-row index that appears valid. Furthermore, the left shift might make an invalid start code appear valid by discarding the highest bit. This has been fixed by checking directly after avpriv_find_start_code has returned. Fixes ticket #8162 (which is about the undefined left shifts). 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.