Hi,
Please link the gstreamer pipeline like this and try again:
... ! nvv4l2decoder ! 'video/x-raw(memory:NVMM)' ! nvvidconv ! video/x-raw,format=NV12 ! appsink
Either NV12 or I420 should work fine. May refer to this sample:
Gstreamer decode live video stream with the delay difference between gst-launch-1.0 command and appsink callback - #6 by DaneLLL