[MPlayer-dev-eng] Re: [MP] Re: [MP] [PATCH] "turbo" mode

[Michael Niedermayer]

Hi

On Friday 17 September 2004 18:37, Loren Merritt wrote:
> On Fri, 17 Sep 2004, Guillaume POIRIER wrote:
> > Le jeu 16/09/2004 à 23:34, Matthias Wieser a écrit :
> >> Am Mittwoch, 15. September 2004 22:01 schrieb Guillaume POIRIER:
> >>> How do I do that?
> >>
> >> Add "psnr" to your lavc options. Then you will find a file named like
> >> "psnr_342234.log". This file contains psnr numbers for each individual
> >> frame. You could plot those numers, calculate differences between
> >> different passes/options/... and so on.
> >
> > Ok, I didn't think about having a look at the psnr log (though I always
> > add psnr to lavc options)
> > Having a quick look at the log files, on the one hand, I saw that around
> > 2/3 of quantizers are the same, which seem to be a good point, on the
> > other hand pretty much all psnr per frames are different.
> > If I plot with main/TOOLS/plotpsnr.pl both psnr, the global psnr curve
> > is quite similar, although with "turbo" there some "outliers" (quants
> > are [2-8] with turbo, whereas without they are [2-7]).
> > Those outliers aren't many, but they exist, which means _if I understand
> > rate-control quite alright_ that at some point the rate-control had a
> > bitrate shortage, and had to raise some quants.
> >
> > Now, this analysis is only based on quants.
>
> Quants are a pretty coarse measure. The actual parameter output by
> rate control is lambda (lagrange multiplier), which is continuous. so you
> might have a frame that wanted quant=1.6 (rounded to 2) on one pass, and
> 2.4 (rounded to 2) on the other. But you can't see the actual lambda
> unless you modify mencoder to output another divx2pass.log on the second
> pass (attached).

applied

[...]

-- 
Michael
level[i]= get_vlc(); i+=get_vlc();  (violates patent EP0266049)
median(mv[y-1][x], mv[y][x-1], mv[y+1][x+1]); (violates patent #5,905,535)
buf[i]= qp - buf[i-1];    (violates patent #?)
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