pulseaudio problems

[Luke Yelavich]

On Mon, Feb 23, 2015 at 12:41:11PM AEDT, Micha? Zegan wrote:
> I have the problem that on the login screen, and separately after
> login, sound (and this means synthesizer/speech-dispatcher) is very
> bad. The problem persists for a second or for few minutes, not sure
> what it depends on...

What distribution, and what version of pulseaudio are you using?

> I believe the problem may be known to some of you, so I ask:
> Is this a problem of pulseaudio or a problem of speech-dispatcher? I
> believe that other programs running on the computer that play sound do
> not have this problem or the problem has a different nature, will have
> to test...

It may be a bit of both. Pulseaudio has had a fair bit of work done on its 
resampling code, which can certainly affect things, particularly since most 
speech synthesizers use a sample rate less than 44100Hz, at least espeak does, 
and I even think the ibmtts synth uses 11025Hz.

To conclusively prove one or another, I think tests need to be made using 
material at these lower sample rates, being played through an audio player with 
pulseaudio. This shouldn't be hard to source, as espeak can write audio to a 
file to be played.

Its also hard to narrow down because at least for me, it is intermitant. 
Sometimes I can go a whole day and not get the problem, and other times I get 
the problem barely 5 minutes into my session. If you haven't gathered already, 
I am aware of the problem, and experience it myself.

> If this is a problem of speech-dispatcher, what to do? switch to
> libao? and actually if so why isn't libao the default?

This is another test point. It would certainly be worth testing with the use of 
the libao output driver, with libao configured to use pulseaudio. If you are on 
Ubuntu, then libao support is not built by default for various historical 
reasons that no longer apply, so this is something I need to rectify.

As for libao being default, I think that is certainly worth considering, should 
the pulseaudio glitchy audio problem be hard to fix, although using pulse via 
libao may also exhibit the same problem, which would be conclusive evidence in 
the problem being in pulseaudio.

Thanks for your mail, I am indeed aware of the problem, I just need to find 
time to perform some tests to try and determine conclusively where the problem 
lies.

Luke