Create a block difference mask of two images?

shoopdabloop · 21st November 2009, 10:48

I was wondering how one would go about looking at two frames/clips, dividing each into 8x8 (or 4x4) blocks, and comparing each block in one image to the corresponding block in the other and setting the value of the corresponding block in the mask clip to the SAD of the pixels.

So basically, seeing in which corresponding blocks two images match up the most.

Is this possible in MVTools?

Didée · 21st November 2009, 21:06

Very easy way to get the normalized SAD over 8x8 blocks:

Code:

mt_lutxy(clip1,clip2,"x y - abs").DCTFilterD(14)

Alas, the result may show up a small bug in DCTFilter that never was fixed. (Result should show only solid 8x8 blocks everywhere. But in fact, there are many blocks with a 'stripe' in the middle. The bug can be worked around by adding Pointresize(1/8 resolution).PointResize(1/1 resolution). )

(Ab)using MVTools is by all means possible, but rather slow.
Calculate vectors against same frame {interleave(clip1,clip1)}, re-calculate with MRecalculate on {interleave(clip1,clip2)}, get SAD mask via MMask(), then selecteven().

shoopdabloop · 21st November 2009, 22:48

would this work also? or is BilinearResize not sampling all 8 pixels?

mt_lutxy(clip1,clip2,"x y - abs",chroma="process").bilinearresize(width/8,height/8).pointresize(width,height)

Gavino · 21st November 2009, 23:58

bilinearresize(width/8,height/8) will sample 16x16 pixels at a time.
You could use bilinearresize(width/4,height/4, 2.0. 2.0)[*], which will give you 8x8 blocks, but the sampling is such that you don't get a simple average, points nearest the centre of each block get more weight, varying linearly (maybe that's what you want, I don't know).

* followed by .pointresize(width/8,height/8).pointresize(width,height)

21st November 2009, 10:48	#1 \| Link
shoopdabloop Registered User Join Date: Mar 2009 Posts: 166	Create a block difference mask of two images? I was wondering how one would go about looking at two frames/clips, dividing each into 8x8 (or 4x4) blocks, and comparing each block in one image to the corresponding block in the other and setting the value of the corresponding block in the mask clip to the SAD of the pixels. So basically, seeing in which corresponding blocks two images match up the most. Is this possible in MVTools? Last edited by shoopdabloop; 21st November 2009 at 11:24.

21st November 2009, 21:06	#2 \| Link
Didée Registered User Join Date: Apr 2002 Location: Germany Posts: 5,407	Very easy way to get the normalized SAD over 8x8 blocks: Code: mt_lutxy(clip1,clip2,"x y - abs").DCTFilterD(14) Alas, the result may show up a small bug in DCTFilter that never was fixed. (Result should show only solid 8x8 blocks everywhere. But in fact, there are many blocks with a 'stripe' in the middle. The bug can be worked around by adding Pointresize(1/8 resolution).PointResize(1/1 resolution). ) (Ab)using MVTools is by all means possible, but rather slow. Calculate vectors against same frame {interleave(clip1,clip1)}, re-calculate with MRecalculate on {interleave(clip1,clip2)}, get SAD mask via MMask(), then selecteven(). __________________ - We´re at the beginning of the end of mankind´s childhood - My little flickr gallery. (Yes indeed, I do have hobbies other than digital video!) Last edited by Didée; 21st November 2009 at 21:10.

21st November 2009, 22:48	#3 \| Link
shoopdabloop Registered User Join Date: Mar 2009 Posts: 166	would this work also? or is BilinearResize not sampling all 8 pixels? mt_lutxy(clip1,clip2,"x y - abs",chroma="process").bilinearresize(width/8,height/8).pointresize(width,height) Last edited by shoopdabloop; 21st November 2009 at 22:53.

21st November 2009, 23:58	#4 \| Link
Gavino Avisynth language lover Join Date: Dec 2007 Location: Spain Posts: 3,444	bilinearresize(width/8,height/8) will sample 16x16 pixels at a time. You could use bilinearresize(width/4,height/4, 2.0. 2.0)[], which will give you 8x8 blocks, but the sampling is such that you don't get a simple average, points nearest the centre of each block get more weight, varying linearly (maybe that's what you want, I don't know). followed by .pointresize(width/8,height/8).pointresize(width,height) Last edited by Gavino; 22nd November 2009 at 00:16.