Bryce Seager van Dyk [:bryce] (he/him) - Not reading bugmail Reporter
	Description • 7 years ago

When running mochitests with the `--use-test-media-devices` flag, gst-launch-1.0 will be invoked (if gst-launch-0.1 is not found). The executed command will look something like:

> gst-launch-1.0 videotestsrc pattern=green num-buffers=1 ! v4l2sink device=/dev/video0

On my local this command blocks and does not return to the test harness. This appears to be due to num-buffers=1 not playing nice with the v4l2sink and v4l2loopback module. If instead of the v4l2sink a fakesink is used, the command returns. If instead of num-buffers=1, num-buffers=2 is used, the command returns.

gst-launch-1.0 --version output:
> gst-launch-1.0 version 1.12.4
> GStreamer 1.12.4
> https://www.archlinux.org/

v4l2loopback module compiled from commit f0114b1a81476bcb43a7279d996348a7166ba21.

This can be worked around in the test harness[0] by changing num-buffers=2. I'm less familiar with the other pieces involved so am uncertain as to what the underlying issue is here.

[0] https://searchfox.org/mozilla-central/source/testing/mochitest/runtests.py#755