-- slow firstpass

[IbrahimKh]

I just noticed in x265 that slow firstpass are enabled by default.
Does slow firstpass worth to use? Considering encode speed will be slower down like 1.5-2x than slow firstpass disabled.

I've tried google this but no luck finding proper answer. Thanks.

[benwaggoner]

I just noticed in x265 that slow firstpass are enabled by default.
Does slow firstpass worth to use? Considering encode speed will be slower down like 1.5-2x than slow firstpass disabled.

I've tried google this but no luck finding proper answer. Thanks.
A bunch of recent improvements made the first pass less accurate and useful to base a second pass on. For the moment, you're probably better off doing a 1-pass and bumping up --preset a notch than doing a fast firstpass and a full second pass.

[IbrahimKh]

A bunch of recent improvements made the first pass less accurate and useful to base a second pass on. For the moment, you're probably better off doing a 1-pass and bumping up --preset a notch than doing a fast firstpass and a full second pass.

CRF mode?

[benwaggoner]

CRF mode?

In x265, a 2nd pass of a CRF encode can also provide the same quality smoothing improvements when the VBV is full. I don't believe that would work at all well without a slow first pass.

[Leo 69]

In all honesty I really just don't get it.

Why do a 2-pass encode when according to the development team, 1-pass CRF basically gives same results? Well, except for the fact we don't know the resulting file size...But who really cares about size nowadays?

[Motenai Yoda]

Ben was referring to an encode which hit vbv limits too much and can be improved using a second pass in crf mode.

[benwaggoner]

But who really cares about size nowadays?
Lots and lots of people :)? Anyone delivering on optical disc, download, or streaming, certainly. And a whole lot of threads here are about how to fit a library in a certain capacity of storage.