espeakup, alsa, pulseaudio, and volume levels

[William Hubbs]

Hi Samuel,

On Sun, Oct 24, 2010 at 03:56:00PM +0200, Samuel Thibault wrote:
> Getting back to the issue of volume levels in a future Debian installer
> with software speech synthesis, I've just realized there's direct alsa
> support in espeakup.  Would it perhaps be better to use that instead of
> portaudio?

Unfortunately the direct alsa support is not quite where it needs to be imho.
 
 The latency value defined on line 41 of alsa.c in espeakup seems to be
 system specific.  I'm not sure that there is a generic value that will
 work for everyone.

 What happens is if the latency value is wrong, you get what Chris
 called a "stomping" affect, where several sounds play on top of each
 other.

> In any case, could somebody work on adding an option to set all the
> muted audio levels to a middle value?  The installer could then pass it
> to somehow make sure at least some audio goes through.

The issue here is that the channels are muted by default, and we would
have to find all muted channels and unmute them as well.  From what I
remember that has to be done with alsamixer or something similar from
the command line; I do not know of an API function to unmute sound
cards.

The way we do that for now on gentoo and arch is with scripts
that run as part of the boot sequence.

> Also, the CMD_SET_VOLUME command only adjust the espeak volume, and not
> the actual PCM volume for instance.  I'd say with the option mentioned
> above it should also set all output volumes it can find.

CND_SET_VOLUME is used when the volume is changed either in the speakup
sys file setting or from the keyboard, so I'm not sure you want that to
mess with any volumes other than speakup's volume (espeak's volume
setting is what actually gets adjusted).

I don't know, again, if there is an ALSA API call that will "find all
volumes on a card and set them to a certain level" or not.

If someone knows of something, let me know.

Thanks,

William