Does NVCompositor work with a live src (and omxenc sink)

Hi,
It should be qp value adjusted per new bitrate setting. For checking it it is IDR frame, you can enable the property:

  insert-sps-pps      : Insert H.264 SPS, PPS at every IDR frame
                        flags: readable, writable
                        Boolean. Default: false

and apply the logic in the post: