How to choose between CBR and 2-Pass VBR ?

Question

How to choose between CBR and 2-Pass VBR ?

Hi,
I know alot of virtual ink has flowed about this topic, but I couldnt find the answer I need.

I'm compressing an 83minute feature film to DVD. Source material is 10bit Uncompressed YUV from PAL DigiBeta, sent directly from FCP to Compressor. Compressor is at version 2.0.1, and all ProApp and QT updates are applied.

Compressing at a CBR (ie: 1pass) with a data rate of 7.4Mbps gives a .m2v file size of about 3.3GB and takes about 3hours.

Compressing at 2-Pass VBR with a max data rate of 7.4Mbps gives a file size of about 3.9GB and takes 12 hours+.

Shouldnt the two pass be smaller given the same max data rate?

When I compare the two visually, I cannot tell any difference between them. I'm looking at areas with alot of motion, or with fine detail, or camera movement, but they look about the same.

How to decide which to use?

Many thanks....

G5 Dual2.0 (PCI-X), 4.5GB RAM, 23" Cinema Display, PB G4 Mac OS X (10.4.6)

Posted on Aug 9, 2006 11:14 AM

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Answer 1

Houghts

Level 4

1,749 points

Aug 9, 2006 11:39 PM in response to Matthew London

Hi There
CBR compression is generally better quality - especially out of Compressor 2 - but usually a higher file size that VBR - can't explain your result there. Check fades, dissolves, small text and camera movement for comparsion between the two mpegs. If you still can't tell the difference then use the bigger one if you have the room, if you don't use the smaller one. If the larger file is better but you're worried about disc space then build your disc using the lager one anyway. If after your created the VIDEO_TS file it still too big use DVD2ONE or DVD Remaster to shrink it back down - I doubt you'd see any visiual difference.
Hope that helps
Cheers
B

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