ffmpeg best parameteres for fastest compression on FullHD mp4?

Question

I need to compress a bunch of FullHD(1920x1080, 3Gb, mp4) videos, each ~2 hrs long. Some loss of quality is okay as is the lower resolution. I'm shooting for a 500Mb output video in ~10 min processing time (2080TI Ryzen 9 3900X). It is important for the videos to be completely in sync, so frame x in the input video matches frame x in output. For this, I'm using -vsync 0

My current working settings which get me to ~500MB size in 20 minutes.

ffmpeg -i input_fullhd.mp4 -vcodec libx265 -crf 28 -vsync 0 -vf scale=800:-1 -preset medium output.mp4

I'd like it to be faster with potentially slightly better quality.

My concern is that I'm not utilizing my GPU at all and my CPU shows only 30% utilization. So feels like it should be possible to speed this up. I tried adding -hwaccel cuda but that made things a bit slower.

Are there any other settings I can try that I'm missing to either improve my conversion or utilize more resources for speed?

Thanks

Answer 1

If you want to use the GPU, there is a different codec hevc_vaapi or hevc_nvenc. You can see some examples here and here. I got it to work once but the quality was much more terrible, so I didn't use it much.