I can't remember where I found this but it's what I've been using to downscale and convert the occasional 10bit downloads (using the nvenc GPU acceleration.)

I can't remember where I found this but it's what I've been using to downscale and convert the occasional 10bit downloads (using the nvenc GPU acceleration.) ffmpeg -hide_banner -y -probesize 100M -i "$file" -map 0:v:0 -c:v h264_nvenc -x264-params b_pyramid=2:ref=4:vbv-maxrate=30000:vbv-bufsize=15000 -refs 4 -crf 17 -preset:v fast -profile:v high -b_strategy 2 -rc-lookahead 900 -level 4.1 -pix_fmt yuv420p -color_range 1 -colorspace 1 -color_primaries bt709 -color_trc bt709 -subq 10 -vf zscale=tin=smpte2084:min=bt2020nc:pin=bt2020:rin=tv:t=smpte2084:m=bt2020nc:p=bt2020:r=tv,zscale=t=linear,format=gbrpf32le,zscale=p=bt709,tonemap=tonemap=hable:desat=0,zscale=t=bt709:m=bt709:r=tv,format=yuv420p,zscale=s=1280x720 -c:a copy output.mkv