[pulseaudio-discuss] system-wide daemon

[Colin Guthrie]

'Twas brillig, and Jeremy Nickurak at 09/02/10 19:24 did gyre and gimble:
> On Tue, Feb 9, 2010 at 09:41, Tanu Kaskinen <tanuk at iki.fi
> <mailto:tanuk at iki.fi>> wrote:
> 
>     That's easier said than done. Only one process can have direct access to
>     the sound card at a time. Each user has his own pulseaudio instance
>     running. How do you implement constant access in such scenario? I fear
>     it would require a major redesign effort in pulseaudio. I haven't seen
>     any concrete design proposals enabling simultaneous access for multiple
>     users while at the same time retaining all the desirable properties that
>     the current system has.
> 
> 
> Off the top of my head....
> 
> "root" or other system-level pulseaudio instance opens and owns the
> physical hardware for the entire time a computer is up.
> 
> All the user pulseaudio instances connect through that.
> 
> What's the downside here?

Mainly due to latencies resulting from the IPC mechanism. Currently PA
operates a zero-copy core, but this would likely introduce data copying.

Also user access would then have to be governed by the PA process. Which
user is allowed to access it and for which devices. Console-kit
integration could be used to say which users are active, so we could
authenticate that way in some capacity but how do you implement
multi-seat device allocation with a single PA process?

There are likely many other problems too but you'll probably have to
wait for Lennarts comments to get a full picture.

> Alternatively, rely on the underlying layer to do multiplexing. If the
> hardware supports it, awesome. If it doesn't, let dmix handle it.

Dmix is very smart but it does not support the power saving features
possible in PA.


This whole thing has been discussed to death, and I really don't feel
like being drawn into the whole thing again.

Col

-- 

Colin Guthrie
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http://colin.guthr.ie/

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