From alsa-devel-owner@alsa.jcu.cz  Fri Feb 26 21:30:12 1999
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	Fri, 26 Feb 1999 21:29:50 +0100
Date: Fri, 26 Feb 1999 21:29:50 +0100 (CET)
From: Jaroslav Kysela <perex@jcu.cz>
To: Kevin Duffey <kduffey@inprise.com>
cc: alsa-devel@alsa.jcu.cz
Subject: Re: CVS changes
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On Fri, 26 Feb 1999, Kevin Duffey wrote:

> >As someone else mentioned, it would be nice if this change provided an
> >interface for hardware mixing (like 3d sound and SB environmental
> >extensions). Also, it would be nice if the mixer could support 4 channel
> >and 5.1 channel sound output. And I imagine there are interfaces for
> >multichannel input, too, for 3d sound recording. 
> >
> >I'm not sure all of this falls under the mixer, but what is the current    
> >vision for how 3d sound will be played (both low-level and through the   
> >library)? There are software algorithms we could use in place of actual 
> >3d sound hardware mixing, but we need a nice interface to abstract that
> >as much as possible. Also, are there 3d sound stream formats which need
> >to be supported?
> >
> >I've looked into this some, but if there are people knowledgeable on
> >this topic, it would be great to make sure we get the proper interfaces
> >in place for this.
> 
> I am not sure if I am the one who mentioned this..but I know I said
> something about how DirectX on the Wintel platform handles hardware mixing
> IF a soundcard supports it..otherwise it does software mixing. The same is
> true for Direct 3D. If the hardware supports 3D streams, its mixed in
> hardware. I dont mean to use the DirectX and MS stuff as an example..but
> they do have the right idea. Most soundcards coming out these days have
> some way of mixing auido in hardware, usually the 32 voice synth, or some
> sort of "streams" mixing. 
> 
> Somewhere in the library, maybe at the mixer interface, there needs to be a
> pointer that points to the actual audio mixing routine. This way..if the
> soundcard supports mixing, the pointer can point to whatever the driver
> does to stream the audio channels to the soundcard. If not, the pointer
> points to our software mixing routine (hopefully done at the kernel level
> in the background). 
> 
> Any thoughts?

Yes, imagine: I have got 32 PCM streams. I want apply after mixing some
own effect in the user space (an application). How can I do it with an
hardware accelerator? It's impossible. The better way is to offer to an
application large number of PCM devices. Things are implemented. The work
is finished (except the lowlevel drivers).

							Jaroslav

-----
Jaroslav Kysela <perex@jcu.cz>
Academic Computer Centre, University of South Bohemia
Branisovska 31, C. Budejovice, CZ-370 05 Czech Republic


