[vorbis] Video codec

[Tom Bishop]

Thanx for the description.. ;-)

Would say blocking noise..

It is as if there is not enough info to fill in the details,
so it just paints the block all one color...

Regards,
Tom

----- Original Message -----
From: "Chrissy and Raul" <chrissyandraul at hotmail.com>
To: <vorbis at xiph.org>
Sent: Monday, September 11, 2000 4:58 PM
Subject: Re: [vorbis] Video codec

> MPEG-2, at moderate (20:1 [10 Mbps, CBR, 4:2:0] ) to high compression
ratios
> (40:1 [5 Mbps, CBR, 4:2:0] ), creates several kinds of artifacts.  The
most
> noticeable ones are three:
>
> 1) Blocking noise (blocks that are 8 or 16 pixels square)
> 2) "Mosquito" noise (irregular dots around sharp edges, like letters or
> numbers)
> 2) Low-level DCT noise, crawling dots on flat surfaces
>
> The first is of spatial nature, still/individual images have it.  The
second
> is spatial and temporal (still and moving images have it).  The third can
> only be detected with moving images as flat surfaces move.
>
> Only with Hockey or Basketball you get blocking noise at 10 Mbps, and only
> sometimes.  The three are visible at 5 Mbps.  This is assuming good IBP
> coding.
>
> Color changes and blurring (unless very obvious) are harder to detect
> without side-by-side comparisons.
>
> RAUL LOPEZ
>
> >From: Tom Bishop <Tom at Truly.nu>
> > >
> > > > the MPEG effects were not
> > > > that noticable on a 27" tube, but when played on a 43" projection
> >system
> > > > suffers very noticably.
> > >
> > > Which the best noticable degradation: Ringing? Blocking? Blur? Skewed
> > > areas? In the colors or in the luminance? I'm sorry, I haven't seen
the
> > > tivo in Europe yet.
> >
> >I have replayTV.. I would say "Blocking" ..though I do not have that
> >much understanding of terminology, there are prominent blocks that appear
> >during action.. still shots look reasonable.
> >
> >Regards,
> >Tom
> >
> >
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