Difference between Very slow and fast preset in CRF mode

[iKron]

is there any video quality difference if i use all same settings in CRF, only changes x264 preset?

[jagabo]

Yes. Higher (slower) presets deliver better quality at the same CRF.

[iKron]

thank you for the reply

[sneaker]

Yes. Higher (slower) presets deliver better quality at the same CRF.

I disagree. Quality can go up/down with slower presets at same CRF. Only compression (quality per bit) will always go up with slower presets (except maybe veryslow->placebo).

Example:

preset		ssim		bitrate
ultrafast	0,9931685	6311
superfast	0,9948741	3000
veryfast	0,9918827	1387
faster		0,9938993	1716
fast		0,9942391	1909
medium		0,9943883	1918
slow		0,9945562	1925
slower		0,9946028	1904
veryslow	0,9943008	1771
placebo		0,9945342	1796

(On this sample veryfast has lower quality than ultrafast, veryslow lower than medium.)

[Bernix]

I disagree. You can see that very fast SSIM is bit worst then others. It also create smallest filesize at faster speed. On SSIM it seems very small difference but in few minutes it can create smallest size at faster time. Probably this is exception but it is significant.
Here is graph for 3 min of video. Do not remember if it is H.265 or H.264 but expecting at least similar results.
So it is different look. It do not take in account any PSNR or SSIM.

In 3mins just video SD 720x576 there is 7MB difference at much faster encoding time. So I think very fast will not deliver similar quality. Also it is seems on ssim in previous post by sneaker.


O.k. didn't read last sentence. So same here



Bernix