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aiortc / aiortc

WebRTC and ORTC implementation for Python using asyncio
BSD 3-Clause "New" or "Revised" License
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MediaRecorder: workaround for error "non-strictly-monotonic PTS error" #1170

Open devluz opened 1 month ago

devluz commented 1 month ago

Setting the time_base of the stream to the same of the incoming video tracks fixes errors some receive when recording incoming video tracks.

Original problem: The problem can be reproduced by sending a video stream with more than 30 FPS and attempt to record it via MediaRecorder. Typical error messages start with "non-strictly-monotonic PTS error" or " Application provided invalid, non monotonically increasing dts to muxer in stream ..." related to issues #580 and probably #520

I suspect the root cause is that AV might default to a time base of 1/30 (if rate is set to 30). If the stream is received at 60FPS then two frames will share a timestamp once converted into the new time base. Many WebRTC based senders also do not enforce a fixed framerate so even 30FPS can randomly have two frames too close together and causing this issue.

I tested this with both png and libx264 with no problems discovered so far.

sfarina commented 5 days ago

This fixes an issue I have with consuming a janus stream.