Re: [LAD] MIDI and audio patchbays

> Hello folks!
> One question, I hope it's not too dumb. :-(
> If you have your average patchbay, how does it know, when new MIDI/audio
> ports/clients come to live or die? And how does it know, that some
> connection was killed by some other application.
> Does it simply query it all the time? I wouldn't think so... But perhaps
> I'm wrong...

For ALSA MIDI sequencer, the patchbay program can create an input sequencer
port, and subscribe it to System:announce (0:1) to receive ALSA notifications
about these events: client start/exit, port start/exit, port
subscribed/unsubscribed. You can try this with aseqdump, like the following
sample session:

$ aseqdump -p 0:1
Waiting for data. Press Ctrl+C to end.
Source Event Ch Data
  0:1 Port subscribed 0:1 -> 128:0
  0:1 Client start client 129
  0:1 Client start client 130
  0:1 Port start 129:0
  0:1 Port start 130:0
  0:1 Client start client 131
  0:1 Port start 131:0
  0:1 Port subscribed 129:0 -> 131:0
...
  0:1 Port unsubscribed 129:0 -> 131:0
  0:1 Port exit 129:0
  0:1 Client exit client 129
  0:1 Port exit 130:0
  0:1 Client exit client 130
  0:1 Port exit 131:0
  0:1 Client exit client 131
...

Regards,
Pedro
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Received on Sat Nov 15 00:15:01 2008