[MPlayer-cvslog] CVS: main/libmpcodecs ve_lavc.c,1.111,1.112

[Guillaume Poirier]

Hi,

On Wed, 2 Mar 2005 14:02:54 -0800 (PST), Loren Merritt
<lorenm at u.washington.edu> wrote:
> The 1st pass should be as close as possible to the distribution of
> quants used in the 2nd pass.

That makes sense.


> x264's 2pass is closer to CQP than it is to
> CBR. But even better would be a 1pass VBR mode that uses the same curve
> compression as 2pass.

Do I understand correctly what you mean by saying that what you
recommend above is due to the x246's rate control implementation, not
particularly the "Right Thing To Do"(TM) with every MPEG-x codec?


> (BTW, I recommend vqcomp=.6 or .7 in lavc too, in which case CQP 1st
> pass becomes good there too.)

That's interesting... Taking other people's experience into
consideration, I always set vqcomp=.6 too, but I never understood what
the option was really doing for its documentation is very terse.
Here's what it reads:
vqcomp=<value>
       Quantizer compression, depends upon vrc_eq (pass 1/ 2) (default: 0.5).

Could you maybe enlight me a little bit Loren?
Of course, your explanation will certainly make its way to the man page ;-)

Also, when you say that increasing a bit vqcomp makes constant quant
first pass acceptable, does this parameter influence the first or the
2nd (and subsequent) pass? The way I understand it makes me think that
it kicks in in 2 and up passes, but that's pure guess. I'm not the
video processing expert here....

Thanks in advance for your enlightenment,

Regards,
Guillaume