>From: BIGLER Don (Framatome) >Sent: 27 February 2019 14:55 >To: libav-user@ffmpeg.org >Subject: [Libav-user] Multithreaded Asynchronous Encoding/Muxing > >All, > >I am writing an application that displays, encodes, and muxes live video using >libav as the backend. The audio and video encoding occurs asynchronously in >the background, each in its own thread, such that the encoded packets arrive >to the >av_interleaved_write_frame() function call at different times. H.264 video >encoding by itself works fine. However when I add audio, the audio is out of >sync from the video even though the audio and video pts are in sync (from >avdevice >using >the matroska muxer). The cause of the problem is not clear to me. >Specifically, here are my questions: > >1. Can the av_interleaved_write_frame() function handle multithreaded >asynchronous calls for audio and video streams? >2. The transcoding example uses a filter graph using buffer/abuffer >filters. My current implementation does not use the buffer/abuffer filters >because I am not applying any filters before encoding. Are they required for >my situation? >3. The encoding happens randomly within the stream such that the first pts >received by the muxer is not zero. Is this required? > >I will greatly appreciate any assistance! > >Regards, >Don Bigler
Hi Don, I don’t think that av_interleaved_write_frame() is thread safe. What you could do is gather video and audio in a thread safe queue, possibly order the packets, and then in separate thread send from that queue to the av_interleaved_write_frame(). For me this works fine. Kind regards, Strahinja
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