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