[MPlayer-users] mencoder: effective use of qp, crf params for x264?

[Loren Merritt]

On Tue, 30 Jan 2007, matthew.garman at gmail.com wrote:
>
> So is it fair to say that specifying bitrate=x is generally
> preferred when you have the time to fine tune x---for every
> individual job?  Otherwise, do some initial experimentation with
> crf, find your optimal value and run with it?

bitrate=x is preferred if you have constraints on the bitrate. e.g. if you 
want a movie to fit on a CD. crf is preferred if you want all your encodes 
to be of similar quality, regardless of how that would distribute bits 
between them.
"time to fine tune" has nothing to do with the decision -- you could just 
as well tweak the value of crf.

> Is there a way for mplayer to combine the best of both worlds?
> E.g., something along the lines of using crf on the first pass,
> having mencoder tell you what the optimal bitrate would be, then
> using that bitrate on pass=2?

If you trust crf to decide the optimal bitrate without human intervention, 
then there's no need to do a 2nd pass at all, just keep what crf encoded.

If you want to reserve the opportunity to look at what crf chose and then 
maybe intervene and change the bitrate, then you're asking for the process 
to not be automated, so of course mencoder wouldn't do it all for you. But 
yes you can use crf on the 1st pass before picking a bitrate for the 2nd 
pass.

--Loren Merritt