1 pass or 2?

[zak_swan]

how much of a difference in quality to the human eye does 2 pass VBR have over 1 pass?

[guns1inger]

Personally, I don't see the value in one pass VBR. You cannot predict file size or guarantee correct allocation of rate. If you are going to go one pass, make it a CBR pass. Or use a constant quality (CQ) pass instead.

[zak_swan]

with a 1 pass vbr mainconcept shows the size of the output file before encoding.

[mats.hogberg]

Not enough to warrant double encoding time IMO.

/Mats

[guns1inger]

I wouldn't trust it's accuracy if space was really tight.

[gadgetguy]

It really depends on the quality/content of the source. If you have high action scenes balanced by low action scenes and the source is clean, 2 pass VBR can give excellent results while increasing the amount you can fit on a disk. If the source is noisy or all action, then 2 pass VBR is probably not going to show much difference. In order for VBR to be effective, (not CQ) the encoder needs to be able to "borrow" bits from areas that compress well and use them in areas that need the extra bitrate. CQ is different because it's not trying to meet a specific target size.