[MPlayer-dev-eng] [LONG] PSNR comparison, new source and results

[D Richard Felker III]

On Wed, Jun 16, 2004 at 04:53:49PM +0300, Jan Knutar wrote:
> On Wednesday 16 June 2004 12:18, Romain Dolbeau wrote:
> > Jan Knutar wrote:
> 
> > qpel not only raise the execution time by over 63% on
> > average, it also decrease the PSNR in all case. trell
> > isn't anywhere as expensive, and it does give you a
> > nice improvement all the time. *dia=-2 is a tiny bit
> > better and not much more expensive tha *dia=1.
> 
> I did a comparison of qpel at different bitrates, with very basic 
> options. Source material is the trailer for "Kate & Leopold", from the 
> PAL DVD. It's full screen 4:3, and I encode it unscaled.
> 
> I used mbd=2:v4mv, 2 pass encoding with different bitrates, with and 
> without qpel.
> 
> The findings:
> 
> bitrate < ~750:	qpel decreases psnr
> ~ 750 < bitrate < 2000:	qpel increases psnr
> 2000 < bitrate:	qpel decreases psnr
> 
> Perhaps more interesting is the same expressed in bits per pixel instead 
> of bitrate, like this:

BPP is a useless metric because quality does not scale with pixels. If
anything it scales closer to sqrt(pixels) so you should measure
against bits-per-line or bits-per-diagonal-length.

Rich