Decrease timecost for h264 encoding 8x 1920*1080@30Hz

We are able to see steady fps. You may enable hardware converter at max clock and try again:
Nvvideoconvert issue, nvvideoconvert in DS4 is better than Ds5? - #3 by DaneLLL

The capability is listed in

h264 and h265 encoding can achieve 10x 1080p60