Hi, as some of you might know, I have been working on multithreading for the ffmpeg CLI (as opposed to the libraries) for quite a while now. That work is now finally entering the vicinity of being usable, so I've decided to air it on the ML for comments on the big picture.
Do note that many things still do not work at all, notably * subtitles * bitstream filters * streamloop * filtergraphs with no inputs Many others are probably broken to a larger or smaller extent. I can, however, get some interesting results - e.g. significant wallclock speedup in cases where singlethreaded codecs/filters can now be run in parallel. I am also seeing 10-20% overall clock cycle increase in my tests - for now that is a known bug that will hopefully be addressed later. One of the main themes of this work is separating various bits of functionality in the code - that typically grew organically over years (often in rather random places) - into clearly defined objects with clearly defined responsibilities. At the core of the new world order is the new scheduler object, living in ffmpeg_sched.[ch]. It handles all interactions between the various ffmpeg components, inter-thread synchronization, etc., so the individual components themselves do not need to know anything about threading/synchronization/the rest of the transcoding pipeline. The patches are roughly grouped as follows: * 01-13 Preparatory cleanup. The big thing here is moving fps conversion from video encoding to filtering (see commit message for 20/27 for details) * 14-20 "Fake" threading for encoders/filters. This moves the last two unthreaded components - encoders and filters - into threads. As previously for decoders, this is merely preparatory, since the main thread waits while the encoder/filter thread does its work. The filter patch is unfortunately especially large, because filtering has multiple entrypoints and they all need to be wrapped and unwrapped for communication with the filtering thread. Some features that conflict with threading are also disabled in these patches. That will hopefully change later (though currently I don't see how subtitle heartbeat can work in its current form). * 21 The scheduler itself, merely added without being used * 22-27 Actually using the scheduler. This is split into multiple patches for clarity, but will be squashed in the final form. You can fetch the code from the 'ffmpeg_threading' branch in git://git.khirnov.net/libav. I will also present a short talk about this work at VDD. Comments, questions, suggestions, etc. are very much welcome, both here and there. Cheers, -- Anton Khirnov _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
