mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2025-02-20 07:48:15 +02:00
1998d1d6af
When there are potentially annotation (i.e. metadata) fields to write, au_get_annotations() is called to produce a string with them. To do so, it uses an AVBPrint which is finalized to create the string. This is wasteful, because it always leads to an allocation even if the string actually fits into the internal buffer of the AVBPrint. This commit changes this by making au_get_annotations() modify an AVBPrint that resides on the stack of the caller (i.e. of au_write_header()). Furthermore, the AVBPrint is now checked for truncation; limiting the allocations implicit in the AVBPrint allowed to offload the overflow checks. Notice that these were not correct before: The size parameter of avio_write() is an int, yet the string in the AVBPrint was allowed to grow bigger than INT_MAX. And if the length of the string was so near UINT_MAX that the length + 32 overflowed, the old code would write the first eight bytes of the string and nothing more, leading to an invalid file. Finally, the special case in which the metadata dictionary of the AVFormatContext is empty (in which case one still has to write eight binary zeroes) is now no longer treated specially, because this case no longer incurs any allocation. 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.