[pulseaudio-discuss] Low latency audio in-out application

[Tanu Kaskinen]

On Mon, 2013-08-26 at 15:04 +0200, Svein Seldal wrote:
> On 08/26/2013 02:36 PM, Tanu Kaskinen wrote:
> > No, PA doesn't offer that. Reading and writing to the sound card is
> > handled completely separately, from different threads, so there's no
> > read/write synchronization in the server either.
> >
> > You said that you use a dedicated box for the processing, so using the
> > default sound server doesn't sound like a hard requirement. In that case
> > I recommend using JACK, it's designed for this kind of use cases.
> 
> Thanks
> 
> Too bad. Using PA is convenient, as it's already integrated into most 
> distros. And I am apparently misinterpreting the PA claim "Good low 
> latency behaviour" -- but I guess that this depending on the definition 
> of low latency...
> 
> Dedicated box means that this PC is a prototype for some real-world HW 
> DSP device which the software will later be moved to. Working on a linux 
> application clearly helps development, debugging and observability.
>
> Perhaps it's best to approach ALSA directly for the lowest latency. Have 
> I understood it correctly that PA emulates ALSA, so I need to disable PA 
> for that particular sound device before I can access it directly?

Yes, it's a good idea to make sure that PulseAudio doesn't try to open
the sound card when you are using it (the ALSA emulation doesn't have
anything to do with this, though). The easiest way to do this is to
switch the card profile to "Off" with pavucontrol (in the Configuration
tab).

> OOI: What use has the synchronize stream argument in stream playback?

You can start/stop multiple streams at exactly the same time. I'm not
aware of any real-world uses for that feature, though...

-- 
Tanu