[Ffmpeg-devel-old] Re: [Ffmpeg-devel] Snow motion blocks

Tuukka Toivonen tuukkat
Mon Apr 18 20:20:46 CEST 2005

On Mon, 18 Apr 2005, Skal wrote:

> 	... but SSD(x,) and SSD(x+1,..) will raise accordingly, if
> 	there's noise. So i doubt the SSD is always lower. You have
> 	to be more precise: SSD(x,..) is stained with temporal noise,
> 	whereas D(x,y) is about spatial noise. Imagine the extreme
> 	case where noise is added every two frames...
> 	Anyway, it's sure bilinear interpolation washes out small
> 	spatial noise, but i'm sure there's better denoising filter
> 	around here.

Yes, the formulas give just a hint why
half-pixel MVs are often better than integer pixel MVs,
although this is obviously not always true.

> 	I'm surprised by your results. I've tried the converse:
> 	extrapolate the off-pel position that yields the lowest
> 	interpolated SAD. But whereas the analytical calculations
> 	gives exact results for real numbers, the experiments were
> 	disappointingly bad, because every approximation that departs
> 	from the exact (integer based) syntax ruins the coding
> 	efficiency.
> 	Details at: http://skal.planet-d.net/coding/interpolation.html

Ah. Finally I understand, I hope, your paper main idea. So you
generalize half-pixel linear interpolation into "infinite resolution"
linear interpolation, compute analytically the optimum MV in this
infinite resolution, and then round it to the nearest
half- or integer pixel location.

Interesting idea. I actually found your page when I was looking
for material for my paper, but back then I didn't quite understand it.

Might work nicely if newer standards such as H.264 would use
linear interpolation for fractional pixel interpolation, but as they don't, 
the methods are less useful :(

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