Thanks for the help and the great webinar yesterday. Using the v4l2loopback capability and thetaV loopback example, here are 2 example gstreamer pipelines to grab the video:
As a lossless huffman encoded raw file:
gst-launch-1.0 v4l2src device=/dev/video99 ! video/x-raw,framerate=30/1
! videoconvert
! videoscale
! avenc_huffyuv
! avimux \! filesink location=raw.hfyu
And with default h.264 encoding on a Jetson:
gst-launch-1.0 v4l2src device=/dev/video99 ! video/x-raw,framerate=30/1
! nvvidconv
! omxh264enc
! h264parse ! matroskamux \! filesink location=vid99.mkv
Pro tip, when in install v4l2loopback, use the video_nr option to create the video device somewhere high so it does not get displaced by PnP of other cameras.