[MPlayer-users] lavc vs. xvid (and improving lavc quality)

Jason Tackaberry tack at sault.org
Mon Jun 7 06:05:19 CEST 2004

On Mon, 2004-06-07 at 05:29 +0200, Michael Niedermayer wrote:
> the gamma correction done by eq2 is completly wrong, as gamma correction must 
> be done in rgb space, but eq2 does it in YCbCr, though thats not the reason 
> for the "blocking" artefacts

I guess doing it in RGB space would be really impractical.  Gamma
correction with eq2 might not be precise, but at least it helps.  It's
better than increasing brightness. :)

> ok, thats funny, xvid isnt doing what u tell it to do, just try mplayer 
> -lavdopts debug=1 and look at the qp values, xvid uses qp=1 on every second 

Just based on the bitrate alone I figured xvid was doing something
terribly strange.

> btw, for libavcodec u need vqmin=1 together with vqscale=1 to get qp=1, this 
> is btw a feature not a bug :)

Hey, that explains a lot. :)

> mv0 could theoretically also cause blocking artefacts, but its not the main 
> cause here

Hmm.  Do you think mv0 is worth it for high bitrates?

> another solution is to get _latest_ libavcodec cvs and use 
> cmp=10:subcmp=10:mbcmp=10:dia=3 but this is very new and so might not work as 
> expected yet, theres also a coefficient in the code which still needs to be 
> finetuned or exported

Wow.  WOW.  Did I mention: _WOW_!  This is an _amazing_ improvement.

You're my new deity for this week. :)


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