[pulseaudio-discuss] How to differentiate pause and stop in pulseaudio.

[Ramachandra Rao, Arun Kumar]

Hi Team,


We have implemented a pulsemodule which listens on sink_input_new_hook and establishes connection with AudioManager and based on response from AudioManager, it sends PA_HOOK_OK or PA_HOOK_CANCEL.


And we trigger Stream event request-cork/request-uncork from the pulsemodule to the corresponding sink_input, so that it reaches corresponding client application stream.

This is working perfectly fine for play and pause use-cases.


But, we have also requirement to handle stop uses i,.e client application should be able to differentiate play/pause/stop events.


>From our current understanding, the only way to notify client applications is through request-cork and request-uncork on stream events from server side.

On client side, those could be mapped like below.

  *   request-cork -> PAUSE
  *   request-uncork -> PLAY/RESUME
  *   ? -> STOP

Other possibilities we thought and also experimented to differentiate Stop from Pause are below:

  1.  Unlink the sinkinput from our pulsemodule side based on AudioManager policy decision.
     *   [Concern] - This might lead to ungraceful notification on client side.
     *   [Concern] - client application gets PA_STREAM_FAILED, which is difficult to differentiate whether it is stop or real stream failure at pulseaudio server side.
  2.  We could either add/append custom property in the stream properties about the state(stop) - So, that the client-application can read this custom property from the stream and act accordingly.
     *   [Concern] - Every client-application has to implement this specific handling in addition to cork/uncork handling.
     *   [Concern] - Still some sort of server-side trigger is required towards client so that, they could read this custom property of the stream.
  3.  As stream events are actually textual information, we tried to send 'request-stop' for our use case. And this is transparently transmitted to applications as stream event.
     *   This works fine for client applications that uses pulseaudio api directly.
     *   [Concern] - This is problematic for applications that use GStreamer. because, we need to adapt GStreamer plugins for pulseaudio to handle this custom event 'request-stop'.

Please provide your inputs or suggestions on this matter.
Any help would be highly appreciated.

Thank you
Regards,
Arun

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