Improve Transcode Quality #371
Conversation
leszko
requested review from
Thulinma,
thomshutt and
emranemran
and removed request for
emranemran
|
CI is failing, but it's unrelated to this PR, failing also on master: https://github.com/livepeer/lpms/actions/runs/6022454830/job/16337223769?pr=372 |
|
|
||
| // There's no direct numerical correspondence between CQ and CRF. | ||
| // From some experiments, it seems that setting CQ = CRF + 7 gives similar visual effects. | ||
| cq := p.Profile.CRF + 7 |
There was a problem hiding this comment.
How did you end up with this formula? Lower CQ values typically indicate better quality at expense of compressions. Also encoders typically will pick either CQ and CRF as the main control so I'm not sure if CQ here will actually make a difference. Do you see a difference if we leave out CQ changes here?
There was a problem hiding this comment.
CRF is used by CPU-based transcoding, CQ is used by GPU-based transcoding.
So, only one of these values will be used at the time.
Technically there is no direct numerical correspondence between CQ and CRF, so the other option would be to set both CRF and CQ in our API. But I think it's not a pragmatic approach right now. Most of our transcoders are GPU anyway.
How did I come with cq := p.Profile.CRF + 7, just experimenting with videos. But obviously not for all videos it will give the same results, since technically CRF and CQ values do not correspond to each other.
There was a problem hiding this comment.
The cq := p.Profile.CRF + 7 doesn't quite make sense to me esp since they don't correspond to one another. Also if CRF is CPU only, then why do we need it?
There was a problem hiding this comment.
Explained here: https://discord.com/channels/423160867534929930/1140578841136484402/1149041283583721634
lets discuss more in discord
Add params: - `-preset slow` - `-tier high` - `-cq` / `-crf`
Improve Transcode Quality with:
-preset slow -tier highNote that there will be a separate PR to change
scale_cudatoscale_npp.Related: