[pulseaudio-discuss] Has anyone ever gotten Orca and Pulse Audio to work together well?

[Daniel Chen]

On Sat, Dec 12, 2009 at 2:43 PM, Bill Cox <waywardgeek at gmail.com> wrote:
> I'm trying to narrow down where the problem is that causes the 1/2
> second delay when Orca tries to read text using pulseaudio.  Is it in
> pulseaudio's main code trunk, or in Ubuntu's version of pulseaudio?

alsa-plugins, actually.

The issue seems to be that espeak, in Ubuntu, uses an old version of
PortAudio known not to support PulseAudio adequately.  Further, it is
configured not to use PulseAudio by default but instead routes through
the pulse pcm & ctl ALSA plugin, which introduces latency.  Based on a
bug report[0], I'm going to configure it to use the PulseAudio backend
instead.

> I have googled, but was unable to find a single instance where a blind
> user was able to get Orca working well with Pulse Audio, without the
> 1/2 second delay.  I've also been able to convince myself that most of
> the issues listed on
>
>    http://pulseaudio.org/wiki/UbuntuBugs
>
> are not causing the problem.  In particular, I was able to run
> pulseaudio with nice -11 and rtprio 9, and the delay is still there.
> I haven't yet dealt with the out of date libcanberra.

That wiki page lists some blatantly false information, like MMX/SSE
acceleration being disabled by default.  Also, it is unclear what
"additional modules have been removed" means.  I have raised these
questions in the appropriate PulseAudio venues.  (As one of the de
facto audio maintainers in Ubuntu, this is some pretty serious muck
I'd like to see corrected -- both in documentation and in source
code.)

> Do any of you know of any case where pulseaudio has been configured to
> deliver speech from Orca without the delay?  Is this simply a problem
> now because Ubuntu was the version most blind users preferred before
> Ubuntu switched to pulseaudio?  Has this problem been there forever?

This problem has become exacerbated with the advent of PulseAudio
exposing broken bits in the audio stack: alsa-lib, linux, hardware
itself.  (Note: just because things appeared to work without
PulseAudio does *not* preclude the brokenness of the other parts in
the stack!)

-Dan

[0] https://launchpad.net/bugs/377060