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Conceptually, these are pretty simple to handle, since they are basically equivalent to the case of alpha being absent, since the only thing the destination alpha plane is used for is unpremultiplyng straight alpha. For planar formats, the total number of cases doesn't change in principle, since before this patch we have: - alpha present, overlay straight - alpha present, overlay premultiplied - alpha absent, overlay straight - alpha absent, overlay premultiplied And now we have: - main straight, overlay straight - main straight, overlay premultiplied - main premultiplied, overlay straight - main premultiplied, overlay premultiplied That said, we do gain some cases now that we used to (incorrectly) ignore, like premultiplied yuva420p10. Notably, we can skip defining separate functions for the case of main alpha being absent, since that can be a single cheap branch inside the function itself, on whether or not to also process the alpha plane. Otherwise, as long as we treat "alpha absent" as "main premultiplied", the per-plane logic will skip touching the nonexistent alpha plane. The only format that actually needs extra cases is packed rgb, but that's only two additional cases in total. Also arguably simplifies the assignment logic massively.
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.