[vorbis-dev] Vorbis is low on artifacts but EQ isn't good

Sebastian Gesemann sgeseman at uni-paderborn.de
Wed Sep 4 03:37:11 PDT 2002

On Wed, 4 Sep 2002, Major A wrote:

> > [...]
> I just reported a similar problem on the vorbis at xiph.org list
> yesterday -- they could well be related. As I understand it, it has to
> do with the fact that at high frequencies, oggenc doesn't separate the
> two channels to save bandwidth, but this can lead to a change in
> coherence and therefore a maximum +3dB change in total power in the
> worst case of a 90deg phase difference in the original.

well.. what I was trying to say was..

IF the encoder does not care of the fact, that zeroing out the angle value 
of the sqaure-polare-mapped vector could lead to a 3dB gain, this could be 
the reason of the amplification

Actually, I don't know for now, how the encoder handles this.
I might be totally wrong...


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