[vorbis-dev] Re: Serious, inacceptable artefacts with Ogg Vorbis

ChristianHJW christianhjw at users.sourceforge.net
Wed Sep 18 23:57:16 PDT 2002

"Michael Noisternig" <michael.noisternig at sbg.ac.at> schrieb im Newsbeitrag
news:3D87BCB5.3010800 at sbg.ac.at...
> > I assume c't sent .wav files pre-decompressed?  Are you using any
>  > playback postprocessing (like a 'spatial expander')?  The last time we
> Something comes into my mind. I open my player and listen to the sample
> again. And I don't notice *that* strong artefacts anymore. I open the
> sound control panel and active 'stereo enhancement' and listen again,
> and there are these terrible artefacts again.


A good example how difficult it is to make a good, objective ABX comparison.

For video this is even more difficult, as most video codecs use
postprocessing for playback, so its almost impossible to tell the 'real'
encoding quality, especially if you are the one developing a codec and in
the situation to judge if your latest 'improvement' has any real positive
effects. Of course you are able to 'measure' some things, but this doesnt
really tell you much about the visual perception to human eye.

Windows users can currently participate in a video quality test on
http://www.everwicked.com . The site admin and author of the test,
everwicked, made a basic player that is circumventing all postprocessing and
setting desktop to a fixed resolution and colour depth for every 'sample' .
Of course you dont know what codec is playing at the moment and you have a
limited amount of time to vote the quality afterwards. Several different
sample movies make sure all kinds of test material is used. The test is just
at its very starting point, but i very much like the idea behind the
development of such tools, as i am not aware of anything similar for video
for the time being.

Current codec test list comprises DivX3, DivX5, ON2VP3 ( theora ), and a few
others ...


Sites : http://mcf.sourceforge.net
MCF mailing lists : news://news.gmane.org
Soon : www.corecodec.com

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