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Martin Storsjö
e0e38acd2f
The aarch64 VP9 loopfilters actually violate aarch64 GCS (Guarded Control Stack), even though we marked the code as GCS compliant in846746be4b. This means that builds with GCS enabled, after that commit, will crash when decoding VP9, on future hardware (or current QEMU) that supports GCS. This also goes for ffmpeg version 8.1.1 where the GCS enabling was backported. This matches the fix that was done for hevcdsp in1f7ed8a78d. This issue wasn't observed if running checkasm in QEMU - therefore, I thought all GCS issues had been fixed by846746be4b. (If I would have tested the full "make fate" with QEMU, the issue would have appeared though.) However with the new checkasm, some of the GCS violations do appear even in checkasm. The reason is that the checkasm vp9 test intentionally craft input pixels that attempt to trigger all the individual separate cases in each input buffer (in randomize_loopfilter_buffers). This means that the checkasm tests actually never test or exercise the early exit cases, which are the ones that violate GCS. With the new checkasm, the call to "bench_new" always test running the code at least once, even if not benchmarking. As the input buffers weren't reinitialized between the test and "bench_new", the pixel differences now differ from the initial setup, so that the code now some times (often) would end up hitting the early exit cases. Ideally, the vp9 checkasm test would be repeated to cover all cases of input buffers that allow early exits, in addition to covering the case with all different cases in one block. (cherry picked from commitd05786cf23)
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 means to alter decoded audio and video through a directed graph of connected 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.