Gracefully recover from accidental unlpugging / removal of sound cards

[Sean M. Pappalardo]

Currently, if a sound card is accidentally unplugged while Mixxx is running, the sound stops. That's fine, but when you plug the card back in, you have to go to Sound Hardware, Rescan devices, and Apply in order to get it to play again. This process should be automated so that if an active card goes missing, Mixxx should start scanning the sound devices every half-second or so until the missing device re-appears (or the user opens the sound prefs.) When the device reappears, Mixxx should automatically resume using it without any user interaction.

[Daniel Schürmann (daschuer)]

The solution for this bug might also be a solution for Bug #799526 "mixxx does not play after resume from standby"

[Sean M. Pappalardo (pegasus-renegadetech)]

Also, if a card being used for Vinyl Control input goes missing, Mixxx should immediately switch to Const mode.

[William Good (bkgood)]

The only way to get PortAudio to rescan devices is call Pa_Terminate and Pa_Initialize, which has the side-effect of killing any currently-playing streams. The calls can be stacked (i.e. you can Pa_Initialize Pa_Initialize Pa_Initialize Pa_Terminate Pa_Terminate Pa_Terminate) but the internal structures don't appear to be affected by this. I just hacked SoundManager up a bit to call Pa_Initialize, dump all the device names to the terminal and then call Pa_Terminate on a button press. The playing stream wasn't affected, but the output didn't change when I plugged in a new device. A solution is probably contingent on the PortAudio hotplugging API they're currently working on (see PA ml, trac, etc).

[William Good (bkgood)]

Assigning to 1.11 because I'm imagining the hotplugging API will be live in portaudio in the 4-5 months time before 1.11. but I could be totally off.

[Sean M. Pappalardo (pegasus-renegadetech)]

I was going to say, isn't 1.11 a little too ambitious if we're waiting on upstream? And even if they do it in that timeframe, how long will it take for Linux distros to pick it up? Since PA hasn't done a real release in ages, distro repos are known to let PA stagnate.

[William Good (bkgood)]

I guess I'm not that worried about it, if the PA guys make it, so be it; if not, we have to change the bug milestone. As far as distros go, the Debian/Ubuntu audio packaging group has been happy to package and repository new snapshots of PortAudio as needed.

[RJ Skerry-Ryan (rryan)]

Don't think this is happening in 1.11?

[Sean M. Pappalardo (pegasus-renegadetech)]

PortAudio's hotplug API bug: https://www.assembla.com/spaces/portaudio/tickets/11

[RJ Skerry-Ryan (rryan)]

I don't think Bill's working on this anymore :).

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/6150