[Mp4-tech] H.264: difference between SNR value of encoder anddecoder

[Gary Sullivan]

FYI:
-----Original Message-----
From: Karsten Suehring [mailto:Karsten.Suehring hhi.fraunhofer.de] 
Sent: Friday, August 05, 2023 5:38 AM
To: Gary Sullivan
Cc: alexismt comcast.net; AngelZhang innosis.com.cn
Subject: Re: FW: [Mp4-tech] H.264: difference between SNR value of
encoder anddecoder
I think the POC mode works properly. But the decoder has to "guess"
which original frame is reference by the decoded frame, e.g. when
skipping frames at the encoder or for different POC settings in frame or
AFF coding mode.
The decoder parameter "Poc Scale" has been introduced to adjust these
references. If encoded and decoded pictures match (please check with an
external tool), you shout try playing with that parameter.
Best regards,
Karsten
Gary Sullivan wrote:
> Perhaps the decoder software doesn't adjust for re-ordering when
> computing PSNR?
> 
> -G.
> 
> -----Original Message-----
> From: mp4-tech-bounces lists.mpegif.org
> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of
> AngelZhang innosis.com.cn
> Sent: Thursday, August 04, 2023 8:25 PM
> To: mp4-tech lists.mpegif.org
> Subject: [Mp4-tech] H.264: difference between SNR value of encoder
> anddecoder
> 
> hi,Everyone
>   I set parameter PicOrderCntType as mode 1, and found the output SNR
> value
> of encoder is different from that of decoder with the 264 bitstream
> built
> by encoder.
>   and in my opinion, the decoder's working principle is same as that
of
> hypothetical reference decoder built in encoder. so i have no idea
about
> such a thing.
>   please give me some interpretations.
> 
> thanks a lot!
> 
> 
> best regars!
> angel
> 
> 
> 
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