[pulseaudio-discuss] Accessing audio as root

[Lennart Poettering]

On Sun, 03.01.10 14:21, Colin Guthrie (gmane at colin.guthr.ie) wrote:

> 
> 'Twas brillig, and Ng Oon-Ee at 03/01/10 13:26 did gyre and gimble:
> > So, in my simplistic and user-centric point-of-view, I wonder if
> > speechd-up accepts audio INPUTS? Perhaps it could act as a pulseaudio
> > sink, with the appropriate modules, of course. It starts before the user
> > logs in and only exits after the user has logged out, of course.
> > 
> > The reasoning behind my proposal is simply that root is system-wide by
> > definition (in my understanding), hence why all Colin's proposals have
> > involved speechd-up running as a particular user while all your replies
> > have mentioned root access to pulse....
> 
> 
> I guess a possibility is the following:
> 
> 1. Make console-kit aware of the "idle" state as before.
> 2. Make the speechd-up or speech-dispatcher "headless". i.e. all they do
> is open a pipe (fifo) and pump their synthesised speech to it - they do
> not actually output audio itself.
> 3. Write a PA module that acts as a pulse client that opens that pipe
> and outputs the sound (in actual fact, we could use a combination of
> module-pipe-source and module-loopback for this without writing a single
> line of code in PA).
> 4. Place a script in:
> /usr/lib/ConsoleKit/run-session.d
>  or
> /etc/ConsoleKit/run-session.d
> (I'm not sure which is best)
> which basically does the following (see /usr/bin/start-pulseaudio-x11):
> 
> /usr/bin/pulseaudio --start --log-target=syslog "$@"
> /usr/bin/pactl load-module module-pipe-source source_name="a11y"
> file="/tmp/a11y.socket" > /dev/null
> /usr/bin/pactl load-module module-loopback source="a11y" > /dev/null
> 
> 
> (or something like the above - I could have gotten arguments wrong and
> you may want some channels/rate etc. stuff going on). There may also
> need to be something setup to stop PA from exiting after an idle timeout.
> 
> 
> With all that in place things may just work. Obviously speechd-up would
> have to support multiple clients opening the /tmp/a11y.socket file (and
> it probably shouldn't actually be in /tmp!).
> 
> Does that fit better with your model of things?

Not sure i am convinced. You'd need to switch which PA instance
actually plays back audio when the session changes. Othewise all
sessions would play (or try to play) audio at the same time.

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4