[theora-dev] Analogue artifact estimation

[jbradford at dial.pipex.com]

> I think a lot these kind of artifacts are better handled through
> pre-processing.

Yeah, that occurred to me, too, after I'd posted it :-).

> Something like a temporal smoother can pretty effectively limit pixel
> crawl and the like, and it's a well known fact that simply blurring a
> video makes it compress more efficiently.

Also, interestingly, adding a small amount of noise to a blurred video, (or still image), makes a lot of people percieve it as being sharper.  Of course, the noise-enhanced video is then practically useless for any further processing, but it's an interesting side-effect.

> In fact, many have said that VP3 already pre- and post- filters too
> much, which can lead to blurry video.

Perhaps an option to add noise after decompression might satisfy some people!?  Sounds odd, but if it works...

John.

> ----- Original Message -----
> From: "Daniel B. Miller" <dan at on2.com>
> Date: Sat, 31 Aug 2002 18:31:43 -0400 (EDT)
> To: <theora-dev at xiph.org>
> Subject: Re: [theora-dev] Analogue artifact estimation
> 
> 
> > hi --
> > 
> > Interesting points you bring up.  Realistically, theora is going to be
> > focused more on the definition of the bitstream and issues of
> > audio/video integration into the OGG format.  Advanced thoughts about
> > new codec ideas might be well received at the tarkin list
> > http://www.xiph.org/ogg/vmail.html.
> > 
> > Not to discourage you from thinking about these things as they relate to
> > VP3;  however it's important to note that our primary objective
> > will be to define the bitstream before tackling major improvements in the
> > encoder.
> > 
> >  ___  Dan Miller
> > (++,) CTO and founder, On2 Technologies
> > 
> > On Wed, 28 Aug 2002 jbradford at dial.pipex.com wrote:
> > 
> > > Hi List,
> > >
> > > Just batting a few ideas around here, but would it be possible to
> > > include in to the codec, estimation for common video artifacts that
> > > occur in the analogue world?
> > >
> > > For example, anything that's gone through a composite stage will
> > > likely have dot-crawl and false colour - if we can recognise this
> > > effect in the encoder, we can treat it as a special case.
> > >
> > > Other artifacts that come to mind are:
> > >
> > > * 3-2 Pull down
> > >
> > > * 30/25 and 25/30 FPS conversion artifacts
> > >
> > > * Dropouts, (both noisy, a-la VHS, and solid bars, a-la BetaSP, (which
> > > I believe halves the chroma resolution - can we possibly take this in
> > > to account as well?) )
> > >
> > > * Stobe effect of a CRT filmed by a different scan-rate camera
> > >
> > > * Colour changes in multi-layered painted cel animation, (where a
> > > character is, say, talking, and they repeatedly add and remove a cel
> > > from the top layer, their face flashes bright and dark :-) )
> > >
> > > Infact, existing video compression codecs do a *terrible* job of
> > > encoding hand painted animation, especially anime, despite claims by
> > > well known studios that it is not an issue.  Good motion estimation to
> > > compensate for poor registration of animation would be worth
> > > investigating.
> > >
> > > I think that the problem with all codecs to date is that they are
> > > designed to compress perfect material originating directly from a
> > > camera.  In my opinion, the above *analogue* artifacts are what give
> > > the digital codecs a hard time.
> > >
> > > I'd be very interested on any comments on these points.
> > >
> > > John. --- >8 ---- List archives:  http://www.xiph.org/archives/ Ogg
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> 
>    
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