[vorbis] Dolby pro logic and vorbis

[Vance Roussin]

At 15:00 15/09/2002 +0200, you wrote:
>As far as I know, LAME is able to mantain the informations stored in some 
>audio files in the lower frequencies, useful for a Dolby pro logic decoder 
>to reproduce a surround sound.
>Is ogg able to do it?

Dolby Pro Logic maintains its Decode-ability even when reduced to 22.1khz
8-bit stereo. Needless to say its some pretty durable stuff. As for wether
or not Vorbis knocks out the phase inversion. I'm banking on 'no'. But if
that talk of the higher frequences getting amped when mixed 'dead center'
is true. Then you might hear some stangeness coming out of your center
channel (or worse yet, not) if you  don't pick a quality higher then 5 or 6. 

-vance

FYI: there is no information stored in the lower frequencies rather it is
how the channels are mixed. The decoder detects 'phase inverted' sound and
adaptively redirects it to the surround channel. The center channel is
merely what is most common in both channels redirected and amped up 3dB
(IOW doubled because one channel is not as loud as two.)

<p><p>--- >8 ----
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