Re[2]: [XviD-devel] I haven't been here for 4 days and what I see? :)

[Christoph Lampert]

On Mon, 4 Nov 2002, Radek 'sysKin' Czyz wrote:
> I was planning the following way for GME to work:
> [...]
> - then, we should find GMC using the vectors. It's done now, I think.
> - and then, we should refine GMC vector using real pictures and real
> SADs. This is the slow part.

We should definitely not use the whole picture for this, but 
only the block from which the global vector was calculated. 
And from the beginning we should only consider block with enough 
structure.
Smolic uses a threshhold for absolute value of horizontal gradient and
vertical gradient. Everything below a value (which I forgot) is marked to
be ignored. Maybe if we can re-use interpolated image for
this?
If horizontal interpol is  Hor[x][y] =  (I[x][y]+I[x+1][y])/2 then 

SAD between I[x][y] and Hor[x,y] is (I[x][y]-I[x+1][y])/2  
so it's just horizontal gradient. Same for vertical, of course. 

He also shows that it's good to lowpass filter the image before using 
gradient decent. Maybe we could use precalculated hv-interpolated image
for this? 

gruel