[Gta04-owner] QtMoko audio state work

NeilBrown neilb at suse.de
Thu Jan 17 02:37:58 CET 2013

On Thu, 17 Jan 2013 00:52:57 +0000 Neil Jerram <neil at ossau.homelinux.net>

> The upshot of all that is that I'm now inclined to look more again at
> the other possible solutions, i.e. gta04-gsm-voice-routing (by Radek)
> and alsaloop (as used in SHR).  The simplicity of
> gta04-gsm-voice-routing is appealing, but I know from previous
> experience that it sometimes fails completely.

The only problems that I've had with gta04-gsm-voice-routing is when the
program that plays the alert sound holds on to the audio port for some reason
and thus blocks voice-routing from accessing it.   I could probably fix that
with certainty by a well-placed 'kill' at the start of voice-routing but I
want to work out why it is going wrong first (this is a little program of
mine ... I think it might be confused by getting signals at bad time - I hate
programming with signals).

>                                                 alsaloop in comparison
> has a drastically different and more complex design.  I'm wondering if
> gta04-gsm-voice-routing is unstable _because_ its design is overly
> simple, and if something more like alsaloop is fundamentally needed -
> but I haven't yet worked out even how to start analysing that; any ideas
> would be most welcome.  Also, if we did go with alsaloop, I've no idea
> yet how we might try to add in echo cancellation.

alsaloop is 923 lines while gsm-voice-routing is 673 lines. That isn't
drastically more complex.
The main value-add seems to be sample-rate matching which doesn't seem to be
a big problem in practice (if you  need  it but don't have it you get
occasional clicks.  I don't get any clicks).

What sort of stability problems do/did you experience with gsm-voice-routing?


> That's it for now.  If you've read as far as here, thanks, and all
> thoughts would be most appreciated.  I haven't yet pushed my
> work-in-progress to anywhere public, but can easily do that if people
> are interested.
> Regards,
>         Neil
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> Gta04-owner at goldelico.com
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