Hi,
For using gstreamer, please check
Using gst-launch-1.0 pipeline to Receiving (on target) : Network Source + video decode + video render - #14 by DaneLLL
Please make sure format, width,height,framerate are configured as the mode shown in v4l2-ctl --list-formats-ext. If either one is not coneectly set, it may fail in launching the gstreamer pipeline.
For using jetson_multimedia_api, you can try the sample:
/usr/src/jetson_multimedia_api/samples/12_v4l2_camera_cuda