[MEncoder-users] vqscale or vbitrate for autoselecting a quality?

[Joe Emenaker]

As mentioned a while back, I'm working on a wrapper for mencoder that 
takes a lot of the tedium and guesswork out of transcoding. The goal is 
to have it know the preferred resolution/container/codecs of a bunch of 
different devices (VCD, iPod, PSP, various cell phones, etc.) and you 
just tell the script what device, what quality-vs-size preference, and 
what quality-vs-encoding-time preference, and then it decides which 
codecs to use and which options to invoke.

It's looking like it's going to have a couple of handy features, too. It 
already does auto-cropping, but I think I'm also going to make it detect 
(for DVD's) if it lacks an audio track for your language and, if so, 
automatically add subtitles for your language.

Anyway, where I'm stuck is in having the script auto-choose a reasonable 
bitrate given the resolution, framerate, color-depth, and user's desired 
quality. Just setting the vqscale (for the lavc codec, anyway) strikes 
me as a way of getting a consistent quality regardless of other factors 
like resolution and color-depth... but, from what I can tell, it 
sacrifices the ability to devote more bits to high-motion scenes and, 
hence, negates any benefits of multi-pass encoding.

On the other hand, trying to set the bitrate seems fraught with peril, 
as most of the posts I see here scoff at the notion of selecting bitrate 
based upon bits-per-sec but, frankly, that's all I have to go on.

I'm open to suggestions....

- Joe