From alsa-devel-owner@alsa.jcu.cz  Fri Mar 12 17:05:10 1999
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Date: Fri, 12 Mar 1999 13:08:38 -0300
From: Daniel Serpell Carriquiry <dserpell@mat.utfsm.cl>
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To: alsa-devel@alsa.jcu.cz
Subject: Re: Some proposals
References: <Pine.LNX.3.96.990312110154.1133G-100000@entry.jcu.cz> <36E92285.6E12A627@racine.ra.it>
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Abramo Bagnara wrote:
> 
> Jaroslav Kysela wrote:
> >
> > On Thu, 11 Mar 1999, Abramo Bagnara wrote:
> >
> > > My proposal is that one card has only one pcm device /dev/snd/pcmC0, this device
> > > can be opened multiple time (as many as hardware permits), can be queried for
> > > the number of hardware pcm supported, can be ioctl'ed to select one of hardware
> > > pcm, can be ioctl'ed to set volume, etc.
> > > This give also the possibility to OSS application to use all the hardware PCM
> > > available.
> > > This can be accomplished changing the gold mixer structure from:
> > > mixer channel direction voice
> > > to
> > > mixer channel direction subchannel voice
> >
> > I must say that I don't see any benefit from this solution (the multiple
> > open). ALSA can handle ALSA handle up to 16 PCM devices per soundcard at
> > the current time. This number is only limited by minor numbers and it will
> > be removed in the future when we will use devfs.
> >
> > The problem is not that ALSA doesn't allow the multiple open, but the
> > problem is that we don't have drivers which supports multiple PCM devices
> > (for example for the synthesizer on the GUS cards) yet.
> >
> > I'm not also sure if EsounD doesn't preffer open only one PCM device with
> > more than two PCM voices. This feature is already supported by the GUS
> > driver.
> 
> If all cards that support hardware mixing of many DAC sources work in the GUS
> way (i.e. receive the data interleaved), this proposal is to forget.
> I believed that this was not the only way...
> If I understand well, to receive the data not interleaved we would need a DMA
> channel for every source... Am I right?
> Please apologize my ignorance.
> 
  In ISA world, this is true, but some PCI cards that do BusMastering
can
mix many channels at the same time (ie, Trident 4dwave have 32+32
independent
channels, even at different data format and rates, from arbitrary
address).
  The M$-Win* driver for this card support multiple open, and it's a
real advantage
(the sistem sounds don't stpo while you are listening an mp3 and playing
some
game).
 

	Daniel Serpell
	daniel@mat.utfsm.cl

