Post Syndicated from Lennart Poettering original https://0pointer.net/blog/projects/pulse-davidz-reply.html

davidz: Shams King is
currently working on HAL support in PulseAudio. He’s planning to extend
our module-combine
to automatically combine all available hardware sound cards found with
HAL into a single virtual sound sink. That way, if the user plugs in
an USB loudspeaker set it will automatically output the same audio as
the internal speakers did before. I believe this is the behaviour most
non-technical users would expect from a well designed system.

Right now PulseAudio sink names cannot be used to identify the
underlying hardware devices, since they are generic names like
alsa_output or oss_output2. However, it might be a
good idea to use the ALSA device name
(i.e. alsa_output_hw_0_0) or even the HAL identifier if it is
available. If this
dialog uses the normal GStreamer PropertyProbe API to
query the available devices (and does not use HAL directly), we should
be able to support this easily in gst-pulse
(right now we support this interface in GstPulseMixer, but not yet in
GstPulseSink).

Marc-Andre, I wonder how the differentiation between “Sound events”, “Music and
Movies” and “Audio/Video Conferencing” touches the “role”/”class” model of GSmartMix?

Regarding power saving and PulseAudio: First of all, PulseAudio
right now is intended to be run per-session, just like esd
was. However, there is some incomplete support for running it as
system-wide instance.

I think instead of integrating PulseAudio with
gnome-power-manager the way you described it is probably a better idea
to close the sound device when it is idle regardless if we are in
power saving mode or not, and hope that the driver authors fix their
stuff to not produce any click or pop sounds when the device is opened
or closed. To be honest, all driver/sound card combinations I have
access to work properly in this area.

In ALSA you usually open devices in O_RDONLY or O_WRONLY mode (and not
in O_RDWR) anyway, so falling back to it is not really necessary.