Re: Kernel OSS vs ALSA

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Thu, 14 Oct 1999 19:10:33 +0200

Michael Poole wrote:
> Thomas Sailer <sailer@ife.ee.ethz.ch> writes:
>
> > > * simultaneous multiple streams, with mixing as needed
> >
> > User space IMO
>
> Bad idea IMO. For highly interactive applications (eg games, but also more
> serious applications of VR) you don't want to take (a minimum of) a full
> context switch before the sound card even has a prayer of seeing a new
> audio sample. It's just not reasonable to restrict access to the audio hw
> to one process (telephony while playing MP3s is a good place you want two
> or more processes using the audio hw at once), and if you want to mix that
> in userspace you're going to need a separate daemon process to do
> that.

esd sucks because you don't want it running all the time and you don't
want the delays it introduces. And all the old software. How about this
solution:

- anyone can open /dev/dsp

- if more than one instance of /dev/dsp is open, the ioctls
and so on are routed to a separate mixing module, which fakes
the separate devices and writes to the real one.

This requires two bits of code:

[ changes to sound driver ]
- interface so that mixing module can take over existing and new
/dev/dsp handles and fake their interface
- when /dev/dsp is opened for the second time, turn on mixing module.

[ separate module]
- do mixing and fake multiple /dev/dsps.

-- Jamie

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