Thank you, Frank!
For those interested, here’s a working pipeline for GStreamer in Mission Planner (counterintuitive to use the H265 codec, but that’s the encoding, despite “main.264” appearing in the rtsp URL):
rtspsrc location=rtsp://192.168.144.25:8554/main.264 latency=0 ! queue ! application/x-rtp ! rtph265depay ! avdec_h265 ! videoconvert ! video/x-raw,format=BGRA ! appsink name=outsink
Using that pipeline with wired ethernet directly from the HM30 ground unit, measured latency on the “5k Low Latency” setting is 160-200ms (5 to 6 video frames at 30fps).