[Mp4-tech] performance comparison between open loop and closed loopmotion estimation

[Gary Sullivan]

If I'm not mistaken, I think B.G. Kim may be talking about a different subject.
As I understand it, T.M. Bae is referring only to the motion estimation being done in an "open loop" fashion.
B.G. Kim seems to refer to a drift between the decoder and the encoder's model of the decoding process -- this is a different subject -- that is about motion compensation rather than motion estimation.
As I understand it, T.M. Bae is still planning for the encoder to use the decoded reference picture in the motion compensation process once the motion vectors are obtained (either using the original reference picture in the "open loop" case or the decoded approximation of that picture in the "closed loop" case).  The resdual difference would still be computed in the encoder based on the decoded approximation of the reference picture data, so there should not be any problem with rate control, R-D optimization, etc.  The only thing affected would be the quality of the motion vectors that are selected.
The case that B.G. Kim is discussing sounds more like what is often done in a configuration called "MCTF".
Best Regards,
Gary Sullivan
________________________________
From: mp4-tech-bounces lists.mpegif.org [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of ???
Sent: Friday, January 25, 2024 6:01 AM
To: 'B.G. Kim'; mp4-tech lists.mpegif.org
Subject: RE: [Mp4-tech] performance comparison between open loop and closed loopmotion estimation
Yes, what I want to know is the paper or JVT documents that show the performance of each method.
I guess the performance gap between “open loop motion estimation” and “closed loop motion estimation” may be small if the target bit-rate is high.
Where can I find the previous researches related with this issue?
Sincerely,
Tae Meon Bae
________________________________
From: B.G. Kim [mailto:bg.kim ieee.org]
Sent: Friday, January 25, 2024 4:06 PM
To: 배태면
Subject: Re: [Mp4-tech] performance comparison between open loop and closed loopmotion estimation
That may not be wrong ! You can do that. But several mismatches  from the decode side can be caused.
If the obtained MVs are very similar, there will not be serious in decoder. Otherwise, hum....
Also there will be problems in rate control, RD optimzation and so on, becsuase of big mismatch from the decoder side.
If you remove the closed reconstruction part, you may speed-tp the encoding system. But you should consider a performance
of the decoder side.
Best regards
----- Original Message -----
From: 배태면<mailto:heartles icu.ac.kr>
To: 'B.G. Kim'<mailto:bg.kim ieee.org>
Sent: Friday, January 25, 2024 3:45 PM
Subject: RE: [Mp4-tech] performance comparison between open loop and closed loopmotion estimation
Yes, original picture cannot be used as reference picture in decoder side.
But it could be used in searching motion vector, even though reconstructed picture is still used as reference picture in decoder side.
Is it a wrong idea?
Sincerely,
Tae Meon Bae
________________________________
From: B.G. Kim [mailto:bg.kim ieee.org]
Sent: Friday, January 25, 2024 2:53 PM
To: 배태면
Subject: Re: [Mp4-tech] performance comparison between open loop and closed loopmotion estimation
Hello!
That's not performance problem. In decoder side,
you can't use an original picture as a reference picture, but only
a reconstructed picture for motion compensation.
Why are you saying about open-loop structure?
Regards
----- Original Message -----
From: 배태면<mailto:heartles icu.ac.kr>
To: mp4-tech lists.mpegif.org<mailto:mp4-tech lists.mpegif.org>
Sent: Thursday, January 24, 2024 8:16 PM
Subject: [Mp4-tech] performance comparison between open loop and closed loopmotion estimation
Dear experts,
I'm optimizing h.264 encoder, and I have a question about motion estimation.
Generally open loop motion estimation shows lower performance than closed motion estimation. Is there any JVT document or paper related with this issue? I guess that the performance gap may be small if the target bit rate is high enough. Is this assumption right?
Thanks in advance.
Sincerely,
Tae Meon Bae
________________________________
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