| commit | 9b0f9003dfab6a230d46aaa94091bf509d889f37 | [log] [tgz] |
|---|---|---|
| author | Andreas Rheinhardt <andreas.rheinhardt@gmail.com> | Thu Apr 02 23:07:55 2020 +0200 |
| committer | Andreas Rheinhardt <andreas.rheinhardt@gmail.com> | Mon Apr 20 21:30:46 2020 +0200 |
| tree | 7dbe1e07dcfe78ce25a48a027808ca9523b8505c | |
| parent | 67e957b43a2fdc197018968b0adc2f6a9c04e961 [diff] |
avformat/matroskaenc: Make ebml_num_size() more robust Matroska (or actually EBML) uses variable-length numbers where only seven bits of every byte is usable for the length; the other bits encode the length of the variable-length number. So in order to find out how many bytes one needs to encode a given number one can use a loop like while (num >> 7 * bytes) bytes++; the Matroska muxer effectively did this. Yet it has a disadvantage: It is impossible for the result of a single right shift of an unsigned number with most significant bit set to be zero, because one can only shift by 0..(width - 1). On some architectures like x64 it is not even possible to do it with undefined right shifts in which case this leads to an infinite loop. This can be easily avoided by switching to a loop whose condition is (num >>= 7). The maximum value the so modified function can return is 10; any value > 8 is invalid and will now lead to an assert in put_ebml_num() or in start_ebml_master() (or actually in put_ebml_size_unknown()). Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.
libavcodec provides implementation of a wider range of codecs.libavformat implements streaming protocols, container formats and basic I/O access.libavutil includes hashers, decompressors and miscellaneous utility functions.libavfilter provides a mean to alter decoded Audio and Video through chain of filters.libavdevice provides an abstraction to access capture and playback devices.libswresample implements audio mixing and resampling routines.libswscale implements color conversion and scaling routines.aviocat, ismindex and qt-faststart.The offline documentation is available in the doc/ directory.
The online documentation is available in the main website and in the wiki.
Coding examples are available in the doc/examples directory.
FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.
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.