[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, 2008 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, 2008 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, 2008 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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