tmpg: vbr vs cbr

[itzo]

If I encode a 20 minutes svcd, which setting will give
better quality?
cbr at 2520
or
2 pass vbr
thanks

[Aznboi_nz]

vbr is always better

[ZippyP.]

It depends on what your settings are for VBR. Is your maximum going above 2520? If not, then VBR is not better than CBR at 2520. Having said that, why waste time using VBR on a 20 minute clip when you can encode at the SVCD maximum using CBR. VBR can help limit file size by limiting the average bitrate and allocating bits from low-motion scenes (where they may not be neeeded) to higher motion scenes. I suppose you could call VBR more efficient. If you don't care about file size then just use CBR at the maximum setting.

[jolo]

ZippyP is right on !!

Nothing can be better for quality than setting a constant maximum quality.
VBR is about saving space on the output without losing quality.

When going VBR if it is 1,000 pass won't matter if your settings for min, mid, max are too low.

There is another issue for some, like me about going CBR, it is the fact that I can use my MPEG editor on CBR files, where you can't on VBR files. For that reason and some compatibility issues, I'm using CBR a lot, instead of VBR. Just depends.

For 2-pass SVCD VBR in TMPG I usually make my settings 2520, 1800, 1100 for Max, Mid, Min. How much smaller it would be compared to CBR at a constant 2530 depends on how active the movement is on the movie.

Jon

[itzo]

thank you zippy and jolo for the clear answer.
I want to use cbr for small files because it does the work much faster
than vbr without losing video quality.

[ZippyP.]

You're welcome!

[ZippyP.]

For 2-pass SVCD VBR in TMPG I usually make my settings 2520, 1800, 1100 for Max, Mid, Min. How much smaller it would be compared to CBR ...

Jolo,
VBR with an average rate of 1800 would be about 3/4's the size of CBR at 2500 (1800/2500), video only, as the audio portion doesn't change.