[M4IF Technotes] Common ways to evaluate encoded video quality?

[Liang Cheng]

Hi,
Can anybody give me a hint about the correlation
between the PSNR and subjective quality measurement?  
I suppose some lab might have made this kind of tests.
 Thank you,
Liang
--- "Rob Koenen (M4IF)" <rob.koenen   m4if.org> wrote:
> Thanks Cristophe.
> 
> Good suggestion.
> We'll make a FAQ entry long those lines.
> 
> Best,
> Rob
> 
> > -----Original Message-----
> > From: Christophe Vermeulen
> [mailto:Christophe.Vermeulen   alcatel.be] 
> > Sent: Monday, June 23, 2023 04:05
> > To: rob.koenen   m4if.org
> > Cc: 'Olivier Amato'; Allen H.Y. Chin; M4IF
> Technotes
> > Subject: Re: [M4IF Technotes] Common ways to
> evaluate encoded 
> > video quality?
> > 
> > 
> > Regarding that question, and at the risk of
> beating a dead horse,
> > I would dare to elaborate a bit.
> > 
> > Sure, you are 100% right, but the fact itself that
> people keep asking
> > shows there is a need for some help in this field.
> Maybe some specific
> > FAQ or LFAQ (less frequently asked questions)
> could help.
> > 
> > Could you all consider the following as a very
> humble, incomplete and 
> > maybe (hopefully partially) erroneous start, and 
> > add/complete/correct it ?
> > 
> > - Is there an way to evaluate objectively the
> quality of a bitstream ?
> > 
> >   Although many algorithms exist (insert link
> list), and 
> > several commercial
> >   applications of these algorithms have been
> provided for 
> > years, no single 
> >   method has ever proven better than subjective
> testiing from experts.
> > 
> > - what is exactly PSNR ? 
> >  
> >   PSNR is the most widely accepted objective
> criteria to quantify the
> >   imperfection of a coding algorithm (experts talk
> of HRC) by 
> > comparing
> >   the coding result with the original material.
> Note that 
> > this assumes 
> >   that the original material is "perfect".
> > 
> >   The formula for PSNR is PSNR=10*log10(255^2/MSE)
> with MSE being the
> >   mean square difference of all the luminance
> values (is this correct?
> >   I don't know why this is a peak) 
> > 
> >   One of the interests of PSNR is that it "speaks"
> to humans, since
> >   it gives a result in dB, like analog SNR ratios,
> with more being 
> >   better, and an easy to understand/remember range
> interpretation :
> >   10-20 is poor quality, while 30-40 is acceptable
> and 50-60 is
> >   already very good (for broadcast type of
> applications at least)
> > 
> >   The use of an inverted logarithmic scale also
> allows to give 
> >   more invariance with respect to different
> sequences as compared
> >   to using MSE. (If my calculations are correct)
> >   roughly PSNR = 25,30,35,40 correspond to
> MSE=200, 65, 20 and 6,5 ?
> > 
> > - What is a HRC ? A Hypothetical Reference Circuit
> is a reference
> >   video material that can be used to evaluate
> coding systems. It is
> >   the result of coding (and decoding) some source
> material (SRC?)  
> >   For example, one can create an HRC by adding
> noise, coding using
> >   an algorithm (e.g. MPEG-4 ASP) and its
> parameters (256 kbps CBR,
> >   CIF, ...), creating bit errors, etc.
> > 
> > - It seem that ANSI recently adopted the VQM
> software as the way to 
> >   test objective quality. Does somebody have some
> experience 
> > with that ?
> >   (To be answered)
> > 
> > - Where could I find more information ? See list
> below, add 
> >  
> http://live.ece.utexas.edu/research/Quality/frqa.htm
> > 
> > Comments/corrections welcome. I hope I did not
> derive too 
> > much from the reality 
> > and provide the proverbial 2 cents of contribution
> ...
> > 
> > CVE.
> > 
> > "Rob Koenen (M4IF)" wrote:
> > > 
> > > This questions has been asked several times
> before. Please see
> > >
>
http://lists.m4if.org/pipermail/technotes/2002-August/001081.html
> > > and follow-up, and
> > >
>
http://lists.m4if.org/pipermail/technotes/2002-November/001471.html
> > > and follow-up in addition t the links below.
> > > 
> > > Nothing really beats exper viewing, even with
> few experts.
> > > 
> > > More in general, we now have the great feature
> on our website that
> > > allows you to search the site, including the
> archives, for questions
> > > that may have been asked before!
> > > 
> > > http://www.m4if.org/index_search.php
> > > 
> > > Best,
> > > Rob
> > > > -----Original Message-----
> > > > From: Olivier Amato [mailto:oamato   wanadoo.fr]
> > > > Sent: Friday, June 20, 2023 01:33
> > > > To: Allen H.Y. Chin; M4IF Technotes
> > > > Subject: Re: [M4IF Technotes] Common ways to
> evaluate encoded
> > > > video quality?
> > > >
> > > >
> > > > Hi Allen,
> > > >
> > > > > So, I'm looking for other metrics to have a
> more objective
> > > > view. Any
> > > > > suggestions?
> > > >
> > > > You could maybe take a look at these links :
> > > > -
> > > >
>
http://www.sarnoff.com/products_services/video_vision/jndmetri
> > > x/index.asp
> > > - http://www.genista.com/Products/VideoPQoS.htm
> > > - http://www.opticom.de/
> > > - http://www.vqual.biz/
> > > -
> http://www.its.bldrdoc.gov/n3/video/vqmsoftware.htm
> > > - http://www.vqeg.org/
> > > 
> > > Regards,
> > > 
> > > Olivier
> > >
> > 
> 
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