Hi, I am not that experienced with gstreamer myself. I think other people on this forum have a similar application to you. I hope that other people can help test the gstreamer plugin for the theta and post recipes or examples of use.
This pipeline was contributed by @snafu666 using lossless huffman encoding on an nvidia jetson using the loopback. The input portion would needed to be modified.
gst-launch-1.0 v4l2src device=/dev/video99 ! video/x-raw,framerate=30/1 \
! videoconvert \
! videoscale \
! avenc_huffyuv \
! avimux \
! filesink location=raw.hfyu