[x264-devel] Re: [PATCH] PSNR averages

[Loren Merritt]

On Sun, 8 Aug 2004, Laurent Aimar wrote:

> On Sat, Aug 07, 2004, Loren Merritt wrote:
> > x264 takes the arithmetic mean of frame-wise PSNRs to produce an
> > overall PSNR. This is meaningless. (Extreme case: what do you do with a
> > frame with no error? (infinite PSNR))
> > This patch corrects it to calculate PSNR from the mean squared error.
> >
> > I also replace "PSNR/Size" (which is similarly meaningless) with
> > "MSE*Size". This quantity is probably closer to what someone wants to
> > measure when they think of "PSNR/Size". It also tends to be relatively
> > constant for a given video over a wide range of QPs.)
>  You are right mean PSNR is a bit meaningless, thanks for your patch :))
>
>  Now x264 will compute mean PSNR (as before, used by the JM), average
> and global PSNR.
>
>  Average/global are computed over the whole picture (ie YUV), I hope
> it's ok, if not I will change it to do it over each plane too.

I still think that mean psnr is misleading and useless (it's greatly
skewed by a few pure black frames with psnr=100), but I'm willing to
ignore it and just look at global psnr.
Yes, a sum over all 3 planes at once is ok.

--Loren Merritt

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