Jetson TX1 H.265 video quality

Hi everyone,
Now I am testing H.265 video quality with 1080p@60fps on Jetson TX1
gst-launch-1.0 v4l2src device=/dev/video0 ! ‘video/x-raw, width=1920, height=1080, framerate=60/1, format=UYVY’ ! nvvidconv ! ‘video/x-raw(memory:NVMM), width=1920, height=1080, format=I420, framerate=60/1’ ! omxh265enc control-rate=2 bitrate=4000000 iframeinterval=30 quality-level=2 ! ‘video/x-h265, stream-format=(string)byte-stream’ ! h265parse ! mpegtsmux ! udpsink host=$CLIENT_IP port=5000 sync=false async=false -e

Howerver the quality is not really good, I can see the blocking artifact frequently, especially on back ground (video is played on VLC).
Are there any can tell me what parameters I can change in order to improve the video quality?
Thank in advance,
Best regards.

Please try omxh265enc bitrate=8000000 iframeinterval=30 preset-level=2

Dear DaneLLL,
I have checked with higher bitrate for h.265 encoder (8Mbps, 12Mbps, 16Mpbs), the quality is improve a little bit, but there is still has noise.
I attached a saved video that run with 8 Mbps (see from 15th second), you can see the video quality is bad, especially on back ground.

Could you give me more suggestion.
Looking for your reply.

Have you tried preset-level? And please compare with local file to eliminate effect of network

gst-launch-1.0 v4l2src device=/dev/video0 ! 'video/x-raw, width=1920, height=1080, framerate=60/1, format=UYVY' ! nvvidconv ! 'video/x-raw(memory:NVMM), width=1920, height=1080, format=I420, framerate=60/1' ! omxh265enc bitrate=8000000 iframeinterval=30 preset-level=2 ! 'video/x-h265, stream-format=(string)byte-stream' ! h265parse ! mpegtsmux ! filesink location=a.ts