This is on linux with pulseaudio. I need to record a video with a rather bare-bones recorder that runs in chrome. I decided to fake a camera and a mic so that I can edit the video then use ffmpeg to send the video to a dummy camera created with v4l2loopback and set the chrome input in pavucontrol. This s what I have:

ffmpeg -re -i ~/xxx.mp4 -map 0:v -f v4l2 /dev/video2 -f pulse "alsa_output.pci-0000_00_1f.3.analog-stereo.monitor"

where /dev/video2 is the loopback camera. This seems to work fine, but the audio lags the video by a few seconds. I verified that they are very much in sync by playing the mp4 normally. How do I fix this?

  • Is it a consistent lag or does it change over time?
    – llogan
    Apr 6, 2020 at 18:15
  • The lag seems to be roughly the same after 22 minutes of streaming.
    – melisgl
    Apr 6, 2020 at 21:43


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