Nvidia Official ffmpeg support hwaccel? problem?

i know that nvidia has an official ffmpeg package that support hwaccel, so i download and install it, i use this command to test if use hwaccel:
ffmpeg -i rtmp:// -c:v h264_nvv4l2dec -an -vcodec copy -s 1920x1080 -f flv test.flv
then i use JTOP tool to look status,then i got:
so , it dosen’t work ?
this url show how to install the new ffmpeg:

so ,please tell me!

You have set -vcodec copy in the command line, so it may not decode and re-encode the stream. Please try the command:

ffmpeg -c:v h264_nvv4l2dec -i /opt/nvidia/deepstream/deepstream-5.0/samples/streams/sample_720p.mp4 a.yuv