[Mp4-tech] RE: Why spatial prediction in AVC performed in pixel domain?

[Shevach Riabtsev]

Gary
I compared correlation coefficients among neighboring 4x4 blocks in both
sample domain and frequency one (i.e. quantized coefficients).  It
appears that the correlation in frequency domain is stronger than in
pixel one.  
The only advantage of sample domain spatial prediction I can see is the
arithmetic precision. Indeed, in pixel domain all predictors are 8-bits
width, while in frequency plane the predictors are 12 bits. 
Where I can achieve Q15-E-17 and Q15-F-11 proposals. Could you send me a
link to these documents.
Regards, Shevach
Broadcom
________________________________
From: Gary Sullivan [mailto:garysull windows.microsoft.com] 
Sent: Monday, August 27, 2023 5:46 PM
To: Shevach Riabtsev; mp4-tech lists.mpegif.org
Subject: RE: Why spatial prediction in AVC performed in pixel domain?
Have you actually done any experiments to confirm your belief that the
frequency domain works better on noisy material?
Of course, also, not all material is noisy...
Gisle Bjontegaard proposed the basic concept of the spatial prediction
as part of his original proposals in 1998 for the H.26L project
(Q15-E-17 in July and Q15-F-11 in November).  I believe he had been
playing with such concepts before that as well.  I'm rather confident
that he would not have proposed such a thing unless it was ordinarily
beneficial to compression capability.
Best Regards,
Gary Sullivan
________________________________
	From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Shevach Riabtsev
	Sent: Monday, August 27, 2023 4:51 AM
	To: mp4-tech lists.mpegif.org
	Subject: [Mp4-tech] Why spatial prediction in AVC performed in
pixel domain?
	Dear experts
	The spatial prediction in AVC is executed in pixel (sample)
domain, while in MPEG2 and MPEG4 the spatial prediction (actually
partial prediction) is performed in frequency domain. 
	I think that on noisy material it is beneficial to perform the
spatial prediction in frequency domain in the same manner as
pixel-domain prediction. 
	Say, for each 4x4 block, DCT and quantization is performed, then
the prediction direction and the residual between quantization
coefficients of the current 4x4 block and the neighboring (left and/or
top) is calculated. 
	What was a reason to prefer the sample domain for the spatial
prediction instead of frequency one. 
	 Regards,  Shevach
	Broadcom
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