Why jetson gstreamer plugin nvvidconv not support BGR format output?

There’s ffmpeg package enabling hardware decoding. Please check Jetson Nano FAQ

The implementation is based on jetson_multimedia_api. For further functions, you would need to use the APIs and do customization. Please download source code of the package and build it manually.

Since hardware converter doesn’t support BGR, one possible solution is to convert to RGBA first through hardware converter, and re-order to BGR through software code.