[MEncoder-users] Re: Question: 2-Pass Encoding No Bitrate Specification

[Rich Felker]

On Fri, Sep 15, 2006 at 12:12:24PM -0700, Jon Drukman wrote:
> Rich Felker wrote:
> >On Wed, Sep 13, 2006 at 06:41:57PM +0300, andreil1 at starlett.lv wrote:
> >>The question is - how to get rid of explicit bitrate specification (2- 
> >>pass encoding seem to require)? I would like to use this script for  
> >>batch converting, and there are files with both high and low bitrate.  
> >>Is there something like "best guess by mencoder itself"?
> >
> >2pass is pointless unless you're trying to meet a target bitrate. If
> >you want constant quality use vqscale=2 or 3 but it will waste a good
> >deal of space on scenes that don't need it IMO.. You might be able to
> >overcome this with clever use of the adaptive quantization options..
> 
> so there's no equivalent to mp3 vbr encoding where it uses as little as 
> needed for each frame but can burst up to the maximum if necessary?

This is what just setting qscale will do, but it's not what you want.
The problem is it will burst up too much in order to maintain the
requested quality. What you want is for quality to drop some during
intense scenes but now so much that it looks bad. Like I said,
adaptive quantization options (scplx_mask and tcplx_mask in
particular) may make it possible to do something reasonable with
constant q.

Rich