Thursday, July 13, 2006

PulseAudio and GNOME

Talked briefly to Monty yesterday about PulseAudio and how it would fit into GNOME. Here are some notes, I may be way off, but I thought it would be good to blog them anyway.



Monty!
Monty making an elaborate point about mixing stuff



  • Multiple Soundcard Configuration: The gstreamer sink for PulseAudio should use the same gconf settings as for the gstreamer-hal-gconf sink as discussed here. Then we would be able to reuse the same dialog which would be nice. I have no idea whether this is feasible, desirable or possible in the context of PulseAudio.. But I thought I’d mentioned it anyway, it makes sense to me and… IIRC, a number of applications such as Totem and Ekiga is moving to selecting outputs (using gstreamer) based on whether they output “Sound Events”, “Music or Movies” or “Audio/Video conferencing”.

  • Power Savings: To be honest, I’m not sure whether PulseAudio runs as a system daemon or in the desktop session or whether it’s configurable (sorry, haven’t done my homework). But surely, to me, it needs to run in the desktop session. It should talk to gnome-power-manager, via D-BUS, and keep track of whether the user “prefers power savings over performance” (yes, this is a user preference which defaults to on when running on battery and off when on AC).
    So if “prefers power savings over performance” is enabled as a desktop session wide setting (or if it changes state - it’s a live variable so need to listen to D-BUS signals from g-p-m), PulseAudio should close the file descriptor to files in /dev/audio when there is silence so the kernel drivers can put the sound card(s) to sleep. Not only that, if the sound card is used only for output it should open with O_RDONLY so parts of the sound card can be powered down. Specifically for projects such as OLPC this is important and Jaya Kumar already done the kernel side of this.
    Sure, when the sound card is turned on again there is a slight pop, but users for which this is the end of the world… they can tweak the setting in g-p-m or perhaps use a specific PulseAudio setting to override. But by default, PulseAudio should ask g-p-m so we can suspend sound cards on battery when not used. It’s about saving energy.. think of the kids, Der GrĂ¼ne Punkt, EnergyStar and all that! :-)



In other news, Mitra got a Macbook and she seems thrilled about it so far. Also, I didn’t know that Mitra’s mom have been in outer space.

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