[Tizen General] Tizen Audio Stack

Patrick Shirkey pshirkey at boosthardware.com
Wed Sep 18 06:53:36 GMT 2013

On Wed, September 18, 2013 4:03 pm, Uimonen, Jaska wrote:
> Hello,
> I'm kind of answering to Tom here.
> I agree that having both jack and pulse will increase latency, but..
> I still fail to see how you are making this bluetooth latency thing go
> away with jack. There's still the bluetooth socket or possibly alsa
> over I2S to bluetooth chip etc. We don't have too much control what
> is happening in the bluetooth (will it be jack or pulse) and the delays
> are varying heavily depending what particular device you are connecting
> to bluetooth.
> If we have 30ms of processing time, to me it sounds plenty(?). Anyway if
> we want to make this more reliable we have to give more realtime
> priorities
> to pulse and make the internal buffering to drivers small enough . If
> after
> this things are not working there's something wrong in the buffering
> scheme of pulse. I mean, we are just taking buffers from alsa, possibly
> processing and sending to bt socket and vice versa.
> You could maybe get pulse hick-ups by sending 100000 volume events
> or similar, but also you could get both jack and pulse behaving bad
> by writing bad kernel driver (if we don't have hard real-time, which
> we probably won't have). I don't see how running processing inside
> pulseaudio dsp thread would produce more latency than running the
> same processing inside jack (?).
> I'm just saying that I think this particular bt use case doesn't justify
> moving to only jack solution. And moving to only jack solution would
> bring you more use cases to solve with jack that are now solved in
> pulse.
> br,
> Jaska
> P.S. I can also try to do some measurements myself about the latencies
> inside pulseaudio with the bt handsfree. The bt handsfree should work
> quite ok in current tizen ivi. I hope I would have more time...

I am happy to run some tests on my side too but I can only use a desktop
system at the moment. I will gather the details for a rigorous test
procedure and verify here before starting.

> P.S.S. Is there any hard facts about the amount of latencies introduced by
> jack and pulse combination? I'm running it in my own laptop and quickly
> I'm not noticing too much difference to running pulse only. it is pretty
> fast and responsive. I haven't yet tried the bt handsfree though...

My experience is the combo does not add noticeable latency with larger
period sizes. I have not tested it heavily with minimum period sizes. In
the past there have been concerns about stability at lower latencies but
PA is always being improved so the only real way to know for sure is to
run some tests with the latest codebase.

Patrick Shirkey
Boost Hardware Ltd

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