[theora-dev] Analogue artifact estimation

[Henry Mason]

I think a lot these kind of artifacts are better handled through pre-processing. 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. In fact, many have said that VP3 already pre- and post- filters too much, which can lead to blurry video.

-Henry

----- 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

<p>> 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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