[MEncoder-users] Pulsating I-frames (keyint)

[RC]

On Mon, 11 Jun 2007 19:21:08 -0400
<nicolas.hesler at sheridanc.on.ca> wrote:

> I've noticed that on certain videos,  pulsating occurs on keyframes
> (I-frames),and especially visible in darker picture areas.  

That's common after vpass=1, but I've never noticed that after the
second pass.

> 1.  Can someone help me with other parameters that might solve the
> issue in a different way? (From what I gather it has something to do
> with manipulating quantizers? But with so many parameters and so many
> that seemingly affect one another, I don't know where to begin.)

Try vqblur=0.2:vqcomp=0.8 OR vqblur=0.8:vqcomp=0.2, one of the two
should improve things, and I'd bet on the first.

I also recomend trying once without the *cmp=2 options to see if it's
causing the problem.

> 2.  Are there drawbacks to setting vi_qfactor and vi_qoffset to the
> values I chose? (Am I sacrificing quality?)

Any time you change how the available bits are allocated, you are
sacrificing quality in one place, for better quality in another.  It's
all about perception, so if it looks better, it is better.