[Mp4-tech] PSNR of Full Search

[Dotan Levi]

Full search don't intent to find the "real" motion, just the minimal
sad, sometimes the minimal sad is the "bad" choise.
Regards,
Dotan D. Levi
________________________________
From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Gary Sullivan
Sent: Wednesday, May 21, 2024 7:44 PM
To: Daniel, Ilan; Peace; mp4-tech lists.mpegif.org
Subject: RE: [Mp4-tech] PSNR of Full Search
That is probably the main reason.  Here are a couple of more
possibilities:
1) "full search" often has a seriously-limited search range (e.g. plus
or minus 16 samples) -- the "fast search" may not be limiting its search
to the same range.
2) "full search" often only refers to an integer-MV value search, with a
limited number of fractional sample grid positions being checked as a
next stage MV refinement operation -- the "fast search" may generate
more sensible motion vectors that work better as a seed for the next
stage of fractional position refinement search.
Best Regards,
Gary Sullivan
________________________________
	From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Daniel, Ilan
	Sent: Wednesday, May 21, 2024 2:51 AM
	To: Peace; mp4-tech lists.mpegif.org
	Subject: RE: [Mp4-tech] PSNR of Full Search
	Hi,
	Any ME implementation (Fast or Full) is usually trying to
minimize a metrics target function (usually involves SAD calculation), 
	but the real function that need to be minimized is number of
encoded bits for certain quality/PSNR.
	therefore it is possible that Fast search will get MV's that
give better result.
	Regards,
	Ilan Daniel
________________________________
	From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Peace
	Sent: Wednesday, May 21, 2024 12:21 PM
	To: mp4-tech lists.mpegif.org
	Subject: [Mp4-tech] PSNR of Full Search
	Hi,
	Sometimes the PSNR of Fast search ME algorithms is better than
that of Full Search.
	How this can be explained?
	Thanks
	Humaira
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