Low latency preview applications for a v4l2 USB capture device / aspect ratio problems

Software & Operating Systems Linux
1

So I have one of those cheapo USB 2.0 HDMI capture devices that actually are close to the lowest latency you can get out of a USB capture device. There’s a few better options but they cost 10 times more.

Anyway, after configuring it correctly (need to set it to BRG3) it performed pretty well as a preview screen in OBS. The trouble is, it seems to stretch 4:3 resolutions to 16:9 and I don’t see how to fix this through OBS.

Are there other options that might be able to change the aspect ratio? gstreamer? I’m curious about them not just for the aspect ratio change but also because OBS isn’t exactly how I want to use this. I’d rather be able to just pop open a preview window from the command line ready to go.

2

Yeah sure. Have you tried mplayer? Something like:

mplayer tv:// -tv driver=v4l2:device=/dev/video0:width=1280:height=720:fps=30:outfmt=yuy2

Might need to change the outfmt, width, and height fields though.

3

Thanks, that works and without the scaling of the preview window I’m actually surprised how sharp it is.

That said, the latency is noticeably poorer with this command than when I used OBS. OBS had poor latency as well until I enabled the BGR3 (emulated) option for the video format of the device. I’m not sure if that can be done through mplayer?

Edit: N/m, just looked up the mplayer man. Oddly literally all the other options have decent latency than that one.