From alsa-devel-owner@alsa.jcu.cz  Wed Jun 24 21:52:09 1998
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From: Frank van de Pol <F.K.W.van.de.Pol@inter.nl.net>
Message-Id: <199806241714.TAA25117@obelix.fvdpol.inter.nl.net>
Subject: Re: 16 digital stereo channels
To: alsa-devel@jcu.cz
Date: Wed, 24 Jun 1998 19:14:42 +0200 (MET DST)
In-Reply-To: <Pine.LNX.3.96.980620114220.15479G-100000@entry.jcu.cz> from "Jaroslav Kysela" at Jun 20, 98 11:57:56 am
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Jaroslav Kysela wrote:
> 
> > As you will notice, it is labeled nicely there for you in the source.  Now,
> > as one might imagine, pcm2, pcm3, pcm4, etc. could probably be easily added
> > by a little inspection of the existing code.
> 
> It's true, but you must remember, that stereo playback over original GF1
> chip eats some CPU time. Data for two or more digital channels must be
> separated for each voice and transferred over DMA to onboard RAM. For
> InterWave chip exist interleaved DMA, but this method of transfer isn't
> used in ALSA driver (yet)..
> 
> If I'll have some time, I'll try play with existing code to extended GF1
> playback to allow some (probably 4) stereo digital audio data play 
> simultaneously from 4 applications... This will allow use up to 5
> applications with GUS MAX/PnP/Extreme which have extra codec..
> 
>

Wouldn't this solution be as CPU intensive as simply performing the mixdown
in software? If so it would be an better idea to provide mixing of multiple
audio streams to one (or more?) DACs. That would work with all soundcards.
One consequence to keep life simple is that all the applications should be
happy with using the same sample rate (otherwise the driver needs to do some
sample rate conversion which is quite tough when done good...)
 
Frank.

+---- --- -- -  -   -    - 
|Frank van de Pol                  -o)
|F.K.W.van.de.Pol@inter.NL.net     /\\
|                                 _\_v
|Linux - Why use Windows, since there is a door?

