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Andreas Rheinhardt b645138a34 avcodec/mpegpicture: Don't copy unnecessarily, fix race mpegvideo uses an array of Pictures and when it is done with using them, it only unreferences them incompletely: Some buffers are kept so that they can be reused lateron if the same slot in the Picture array is reused, making this a sort of a bufferpool. (Basically, a Picture is considered used if the AVFrame's buf is set.) Yet given that other pieces of the decoder may have a reference to these buffers, they need not be writable and are made writable using av_buffer_make_writable() when preparing a new Picture. This involves reading the buffer's data, although the old content of the buffer need not be retained. Worse, this read can be racy, because the buffer can be used by another thread at the same time. This happens for Real Video 3 and 4. This commit fixes this race by no longer copying the data; instead the old buffer is replaced by a new, zero-allocated buffer. (Here are the details of what happens with three or more decoding threads when decoding rv30.rm from the FATE-suite as happens in the rv30 test: The first decoding thread uses the first slot of its picture array to store its current pic; update_thread_context copies this for the second thread that decodes a P-frame. It uses the second slot in its Picture array to store its P-frame. This arrangement is then copied to the third decode thread, which decodes a B-frame. It uses the third slot in its Picture array for its current frame. update_thread_context copies this to the next thread. It unreferences the third slot containing the other B-frame and then it reuses this slot for its current frame. Because the pic array slots are only incompletely unreferenced, the buffers of the previous B-frame are still in there and they are not writable; in fact the previous thread is concurrently writing to them, causing races when making the buffer writable.) Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>		3 years ago
compat	compat: add msvc windres wrapper	3 years ago
doc	lavu/hwcontext_qsv: add loader field to AVQSVDeviceContext	3 years ago
ffbuild	…
fftools	fftools: add DPI awareness manifest	3 years ago
libavcodec	avcodec/mpegpicture: Don't copy unnecessarily, fix race	3 years ago
libavdevice	configure: always enable gnu_windres if available	3 years ago
libavfilter	avfilter/vsrc_ddagrab: add options for more control over output format fallback	3 years ago
libavformat	configure: always enable gnu_windres if available	3 years ago
libavutil	avutil/hwcontext_d3d11va: add support for rgbaf16 pixel format	3 years ago
libpostproc	configure: always enable gnu_windres if available	3 years ago
libswresample	configure: always enable gnu_windres if available	3 years ago
libswscale	configure: always enable gnu_windres if available	3 years ago
presets	…
tests	lavu/pixfmt: add packed RGBA float16 format	3 years ago
tools	tools/target_dec_fuzzer: set avctx->workaround_bugs flags	3 years ago
.gitattributes	…
.gitignore	…
.mailmap	…
.travis.yml	…
CONTRIBUTING.md	…
COPYING.GPLv2	…
COPYING.GPLv3	…
COPYING.LGPLv2.1	…
COPYING.LGPLv3	…
CREDITS	…
Changelog	lavc/vaapi_encode: enable 8bit 4:4:4 encoding for HEVC and VP9	3 years ago
INSTALL.md	…
LICENSE.md	…
MAINTAINERS	MAINTAINERS: Add ED25519 key for signing my commits in the future	3 years ago
Makefile	Makefile: Prompt for reconfigure on lavc/hwaccels.h modification	3 years ago
README.md	…
RELEASE	RELEASE: update after 5.1 branch	3 years ago
configure	compat: add msvc windres wrapper	3 years ago

README.md

FFmpeg README

FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.

Libraries

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 means to alter decoded audio and video through a directed graph of connected 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.

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, ismindex and qt-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.