[theora-dev] Analogue artifact estimation

jbradford at dial.pipex.com jbradford at dial.pipex.com
Wed Aug 28 00:58:35 PDT 2002

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.

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