[Alsasrc] System hang once disconnect the device, while pipeline is alive

[Tim-Philipp Müller]

On Thu, 2012-12-20 at 04:58 -0800, Ralph wrote:

> > Now if i get the sound card removal event in time i set the pipeline state
> > to null and everything works fine.
> 
> Can I ask what is this "sound card removal event"?  I have a similar problem
> on Windows ( my question
> <http://gstreamer-devel.966125.n4.nabble.com/How-to-handle-disconnecting-the-headphones-td4657352.html> 
> ) - when I disconnect the audio device, the pipeline stalls and it is not
> possible to play it again.
> How can I detect situations when an audiosink's device has been disabled or
> disconnected?  I will have no problem reconfiguring the pipeline to allow
> playback, but I need to know when it happens.

In this case it was an USB audio device.

The various alsa functions would just return an error with a ENODEV
error code if I yank the cable during recording/playback, but I assume
there's some kind of event notification in upper layers (usb/udev/device
manager) as well.

Cheers
 -Tim