[XviD-devel] problem

[skal]

On Fri, 2003-04-04 at 18:05, elcabesa wrote:
> i'm testing lot of stuff of xvid an i'm very happy about result=)
> the only oine problem/bug i found is that enabling qpel in fixed quant 
> encoding make psnr go down
> you cannot notice it in a cbr encoding couse bitrate saving  make xvid using 
> an  lower quantizer   so psnr raise =)
> 
> i don't know if it's a know effect of qpel, or if it's due to interpolation 
> reuested by standard

	So far I've seen, it's an effect of the interpolation required
	(6taps FIR+mirroring) by the norm: even at hpel position, the
	psnr lowers significantly (~.3db or worse) when using qpel.
	( i mean: if you take the mv found by hpel search and simply
	promote them qpel mv without any further refinement search,
	the psnr lowers). Good candidate scenes for qpel are still
	to be found (but Michael (M) has some hints ;)

	later!
		Skal