How to do audio with ffmpeg/v4l2/oss?

From: Mason Loring Bliss <>
Date: Sat, 30 Apr 2022 19:23:40 UTC
Hi all! I do this on Debian to present a video with audio over Jitsi:

ffmpeg -re -ss 00:00:00 -i foo.mp4 \
    -map 0:0 -f v4l2 -c:v rawvideo /dev/video100 \
    -map 0:1 -f alsa hw:aloop100,1 &

I'd like to do the equivalent on FreeBSD, and on my first pass I got video
working, but not audio. I see the oss filter built into ffmpeg, but I'm not
sure how to point it to a device or what that device might then be. It's
been a while since I tried and this might not be the right video syntax,
but I'm mostly curious about what the right thing to do is for the audio:

ffmpeg -re -ss 00:00:00 -i foo.mp4 \
    -map 0:0 -f v4l2 -c:v rawvideo /dev/video100 \
    -map 0:1 -f oss [INSERT MAGIC HERE]

Note that I'm not tied to the idea of using ffmpeg for this - it's just
what works on GNU/Linux, and it seems to at least mostly work here.

I'd be grateful for advice.

Mason Loring Bliss          Ewige Blumenkraft!
awake ? sleep : random() & 2 ? dream : sleep; -- Hamlet, Act III, Scene I