Alsa/Pulseaudio conflicts

[Hynek Hanke]

Hello Gilles and others,

> After the Ubuntu speech dispatcher package has been installed (currently 
> system-wide), there is no sound at next login: sd uses alsa which 
> prevents a correct start of the user's pulseaudio session (pa 0.9.10).
> I guess that distros could provide a new sd package for avoiding this 
> conflict, e.g. :
>   
In principle, this is only a problem if this system-wide Speech
Dispatcher uses ALSA, not PulseAudio directly. It should
be possible to set it up to use PulseAudio in such a way that it
doesn't block any other PulseAudio applications nor Speech Dispatchers
running inside user sessions. There is also no problem if the
user doesn't run PulseAudio at all. I agree that distributions must
make some decision about it and should provide a setup
that works, because mixing these two things brings troubles,
as you described.

PulseAudio is a necessary and good way how to finally
solve the problems we are constantly facing with audio
output. One such example is the independent controll
over the volume level of different clients -- in other words,
raising the volume of Speech Dispatcher voice output,
a repeated requirement currently impossible to accomplish
with the architecture of just Alsa. But of course this is only
one of the numerous technical advantages of having an audio
system.

 From the standpoint of a developer of Speech Dispatcher who
has some non-trivial knowledge about the various sound susbsystems,
I can tell that the current direct ALSA sound output in Dispatcher is
very limited, has problems that are non-trivial to fix and we don't
like it. PulseAudio could be a huge improvement.

The current implementation of Pulse Audio in Speech Dispatcher
is slow because the implementation of it contains a problem.
For each sound output, it opens and closes the whole connection,
so there is a big overhead which is completely unnecessary.
We believe PulseAudio will be much faster once this is solved.

Gilles, please, do you believe you could find some time
to fix this reopenning problem? I think this is the biggest
obstacle right now.

Thank you,
Hynek Hanke