[vdr] Re: 5.1 Sound with analog soundcard?

["Dr. Werner Fink" <werner@suse.de>]

On Fri, Jul 04, 2003 at 09:32:01AM +0200, gfiala@s.netic.de wrote:
> Zitiere hm@seneca.muc.de:
> 
> > Jarkko Santala <jake@iki.fi> wrote:
> > > Just to clear one thing up: there is _no_way_ to get 5.1 sound from
> > > stereo, what you can get is dolby surround which is 4 channels (left,
> > 
> > Well you can always do something artificial but you basically cannot
> > generate information (signals) from nothing. 
> 
> You are right to "normal stereo" but "surround (stereo)" does contain a certain
> amount of information for the rear and center-speaker which is simply thrown
> away in that cases. There is analog equipment available in TVset's to make use
> of it,
> but so far i know of now sound-card that makes the same, even if it claims to be
> a 3d-card. The reason is probably simple - the price d*lby requires for doing
> that is so high, that it might easily double the price of cheap soundcards,
> therefore you get none.
> 
> I apologize that i brought that thread up, i see now that it leads nowhere.

... just to say it: with the phase differences/correlations between left
and right channel together with the information about audio frequencies and
the corresponding free air wavelengts you're able to determine the virtual
direction of the audio source at recording time.  This holds true for
normal stereo ... the surround technique uses this to mix down more than
two audio sources together with the appropiate phase differences/correlations
to increase the surround effect for the rear audio information.
With the help of some physiognomic informations about head and ear of a
human and some information about physioacustics models this may lead to
the perfect isolution ;^)  ... now Dolby Labs Inc. have casted such things
into real hardware.


       Werner


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