Is VBR 2 Pass that much better than VBR 1 Pass or CBR?

[Walter Soyka]

[Oscar Gotti] “So if I understand correctly the only scenario where 2-Pass VBR would not give better quality would be when the bit rate is set to maximum? “

2-pass VBR is not automatically better than CBR. It’s just more space-efficient. Which is better in terms of image quality depends on the bit rate.

[Oscar Gotti] “Unless you’re working with Blu-ray surely this is very rare… and so using the 2-Pass option should be used every time (if time allows)?”

I’d hesitate to make a blanket statement like that. I do a lot of delivery for systems which require constant bit rate for best performance. Depending on the constraints you place around VBR, it’s possible to create bitrate spikes that the player or transmission system cannot handle in real time.

[Oscar Gotti] “I don’t know of anyone who sets their bit rate to 100+Mps when exporting to Youtube for example, so surely 2-Pass should be used every time for beter quality?”

YouTube is likely to recompress your content anyway. You could use a high constant bit rate.

2-pass VBR, peaking at 10 Mbps will not yield better image quality than CBR at 10 Mbps, but the file will be smaller and the encode will be longer.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive   |   RenderBreak [blog]   |   Profile [LinkedIn]

[Walter Soyka]

VBR has a minimum bit rate (the floor below which it will not fall), an average bit rate (the target as a whole), and a maximum bit rate (the ceiling above which it will not rise). I was discussing that peak maximum rate above.

VBR will look better than CBR if it can peak above the CBR bit rate; it will not look better if it peaks at the CBR bit rate but averages below.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive   |   RenderBreak [blog]   |   Profile [LinkedIn]