Constant or Variable - what is best

[jgarnold]

Apart from the fact that you can 'fit' more (minutes of) video onto a DVD when authored with VARIABLE bit rate is there any difference in quality on playback or compatibility with stand alone players between DVDs authored with CONSTANT or VARIABLE bit rates?
Most of my videos (made from camcorder) easily fit on a DVD using 8000kbs CONSTANT but I was just wondering if I would be better using 8000kbs VARIABLE.
Thanks John

[redwudz]

I would usually say that VBR is better to conserve bitrate on the slower scenes to use on the faster scenes. But using VBR it is harder to predict filesize.

If you need all the space you can get, go with VBR.

CBR should be faster for encodes as the encoder doesn't have to calculate the variable bitrates.

As far as 'best', it depends what you are doing. Compatibility: Don't really see a difference between the modes as long as you stay well within the DVD spec for bitrate.

There are probably more issues involved, but those are the ones that come to mind for me. (IMO always)

[disturbed1]

At a high bitrate, you'll notice no difference between constant and variable bitrates, unless you use CCE. CCE gains more quality as the passes increase, to a point. Once pass (VBR or CBR) doesn't hold the same quality as a 3 pass encode with CCE. In my experience (with TMPG, ProCoder, and Mainconcept), using 500 min, 6500 avg, and 8000 max, 2 Pass VBR, I actually saw spots that looked worse compared to a 6500 CBR encode. Dropping below 6500 avg and 6500 cbr (~5000), with multipass VBR, high action scenes always look beter, and stale scenes look about the same.

With VBR non motion scenes are given fewer bits, while high motion scenes get more bits. Talking heads = low bitrate, car chase = high bitrate. With multipass VBR the encoder attempts to give you a Constant Quality, with CBR encoding, you'll have variable quality.

My cut off is 6500. If I can use that bitrate or higher, I don't bother with multipass VBR encoding.

[lordsmurf]

TMPGENC VBR encoding really sort of sucks. Use CQ or CBR.
I've never seen flaws in PROCODER encodes.

What is best depends on the disc size and how much you intend to squeeze onto it, as well as the encoder and time you're willing to wait. Source may be a factor too. If it's already bad, a few more blocks won't make a big difference.