[Mp4-tech] RE: [jvt-experts] [video] MPEG2 reference encoder SNR question

[Gary Sullivan]

The number in brackets is the PSNR referenced to the peak possible
expressible difference.
It is computed as 10 * log10( 255*255/MSE ).
That is the most common way that video coding fidelity is measured.
It gives you a basic idea of the magnitude of the error.
The number at the end is the SNR referenced to the signal variance.
It is computed as 10 * log10( variance/MSE ).
It tells you how much the fidelity has been increased relative to simply
representing the signal using its mean value.
PSNR will never be negative, even if the coded result is complete
garbage that is totally unrelated to the input signal.
If the output signal is unrelated to the input signal, SNR will almost
certainly be negative.
Best Regards,
Gary Sullivan
+> -----Original Message-----
+> From: Gulistan Raja [mailto:raaja47 yahoo.com] 
+> Sent: Thursday, July 15, 2023 4:57 AM
+> To: mp4-tech lists.mpegif.org; jvt-experts mail.imtc.org
+> Subject: [jvt-experts] [video]
+> 
+> Dear Experts
+> 
+> During encoding of frames using MPEG2 reference
+> encoder, I got following
+> SNR statistics for certain frame.
+> 
+> ...
+> Y: variance=2790, MSE=23.4 (34.4 dB), SNR=20.8 dB
+> U: variance=42.87, MSE=7.15 (39.6 dB), SNR=7.78 dB
+> V: variance=60.01, MSE=4.6 (41.5 dB), SNR=11.2 dB
+> ...
+> 
+> I am confused about the SNR values e.g., in case of Y
+> SNR in above data,
+> whether the correct SNR value of frame  is 20.8 dB or
+> value in brackets
+> i.e., 34.4 dB.
+> 
+> Could anyone please help me in this regard
+> Thanks in advance
+> 
+> Raja
+> 
+> 
+> 
+> 
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+> video coding standardization work conducted by the Joint 
+> Video Team (JVT) of ISO/IEC JTC1/SC29/WG11 (MPEG) and ITU-T 
+> SG16 Q.6 (VCEG).
+> 
+> 
+>