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Commit 1af615683e4a1a858407afbaa2fd686842da7e49 put initializing the ff_fft_offsets_lut (which is typically used if FFT_FIXED_32) behind an ff_thread_once() to make ff_fft_init() thread-safe; yet there is a second place where said table may be initialized which is not guarded by this AVOnce: ff_fft_init_mips(). MIPS uses this LUT even for ordinary floating point FFTs, so that ff_fft_init() is not thread-safe (on MIPS) for both 32bit fixed-point as well as floating-point FFTs; e.g. ff_mdct_init() inherits this flaw and therefore initializing e.g. the AAC decoders is not thread-safe (on MIPS) despite them having FF_CODEC_CAP_INIT_CLEANUP set. This commit fixes this by moving the AVOnce to fft_init_table.c and using it to guard all initializations of ff_fft_offsets_lut. (It is not that bad in practice, because every entry of ff_fft_offsets_lut is never read during initialization and is only once ever written to (namely to its final value); but even these are conflicting actions which are (by definition) data races and lead to undefined behaviour.) 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.