[alsa-devel] Hotplug plugin

Erik Slagter erik at slagter.name
Tue Jan 1 19:26:13 CET 2008

Lennart Poettering wrote:

>>  - pulseaudio, using hal-detection and "combined" device: doesn't work
>> because a removed device is never reinserted into the combined
>> device;
> Of course it is. Just install PA 0.9.7 or newer.

Nope, really.

The relevant config file sections (using pa 0.9.7):


load-module module-hal-detect
load-module module-combine sink_name=all
-> master=alsa_output.pci_8086_27d8_alsa_playback_0
-> slaves=alsa_output.usb_device_8bb_2704_noserial_if0_alsa_playback_0
-> adjust_time=5 resample_method=src-sinc-best-quality

 - or -

load-module module-detect
load-module module-combine sink_name=all master=alsa_output.hw_0
-> slaves=alsa_output.hw_1 adjust_time=10
-> resample_method=src-sinc-best-quality

 - or -

load-module module-alsa-sink device=hw:0 format=s16 rate=44100
-> channels=2 sink_name=alc883 channel_map=left,right
load-module module-alsa-sink device=hw:1 format=s16 rate=44100
-> channels=2 sink_name=jvc channel_map=left,right
load-module module-combine sink_name=all master=alc883 slaves=jvc
-> adjust_time=10 resample_method=src-sinc-best-quality


-> is line continuation

These combinations all yield the same result: at startup I have an "all"
sink that combines both devices, and does that pretty well, I must say.
But as soon as the USB device is removed, it is removed from the
combined "all" sink. Then when the USB device is reinserted, it gets
detected (module-hal-detect) or not (module-detect, static config).
Using module-hal-detect the reinserted just sits there, it isn't added
to the combined sink. Using the other methods, it's not even detected
that the USB device is back...

The only solution I can think of, is a udev script that casts some magic
spells towards pulse when the USB device is inserted or removed... But
then I could skip pulse altogether, because mpd has an option to
activate and deactivate selected outputs at runtime, as well.
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