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Asked: 2020-11-22 05:08:48 +0800 CST

error :Queue input is backward in time when to capture audio with ffmpeg

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Show all sound card in my pc.

pacmd list-sources |grep  name:
    name: <alsa_output.pci-0000_00_1b.0.analog-stereo.monitor>
    name: <alsa_input.pci-0000_00_1b.0.analog-stereo>

Now to capture audio playing via alsa_output.pci-0000_00_1b.0.analog-stereo.monitor.

ffmpeg -f pulse -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor \
       /tmp/out.mkv

I encounter error info:

Queue input is backward in time
    Last message repeated 3 times
[matroska @ 0x562e991d5e00] Non-monotonous DTS in output stream 0:0; previous: 4550, current: 4507; changing to 4550. This may result in incorrect timestamps in the output file.

How to fix it?

sound pulseaudio video ffmpeg alsa

1 Answers

  1. Add -use_wallclock_as_timestamps 1 input option:

    ffmpeg -use_wallclock_as_timestamps 1 -f pulse -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor /tmp/out.mkv

    Note that you will likely get Vorbis audio by default for Matroska output. You can add -c copy if you just want to mux the input PCM audio into .mkv (or .mka).

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