TechNote_Disconnect

Tech Note: Disconnected Streams and Plugin Issues

When Oboe is using OpenSL ES, and a headset is plugged in or out, then OpenSL ES will automatically switch between devices. This is convenient but can cause problems because the new device may have different burst sizes and different latency.

When Oboe is using AAudio, and a headset is plugged in or out, then the stream is no longer available and becomes "disconnected". The app should then be notified in one of two ways.

1. If the app is using an error callback then the AudioStreamErrorCallback methods will be called. It will launch a thread, which will call onErrorBeforeClose(). Then it stops and closes the stream. Then onErrorAfterClose() will be called. An app may choose to reopen and start a new stream in the onErrorAfterClose() method. The onErrorAfterClose() method is called in a thread that is created by Oboe in AudioStreamAAudio::internalErrorCallback(). So the app does not need to create another thread.

2. If an app is using read()/write() calls then they will return an error when a disconnect occurs. The app should then stop() and close() the stream. An app may then choose to reopen a stream.

Bug in P and Q

On some versions of Android P (9), and some early versions of Q (10), the disconnect message does not reach AAudio and the app will not know that the device has changed. There is a "TEST DISCONNECT" option in OboeTester that can be used to diagnose this problem.

Workaround for not Disconnecting Properly

As a workaround you can listen for a Java Intent.ACTION_HEADSET_PLUG, which is fired when a head set is plugged in or out. If your min SDK is LOLLIPOP or later then you can use AudioManager.ACTION_HEADSET_PLUG instead.

// Receive a broadcast Intent when a headset is plugged in or unplugged.
public class PluginBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        // Close the stream if it was not disconnected.
    }
}

private BroadcastReceiver mPluginReceiver = new PluginBroadcastReceiver();

You can register for the Intent when your app resumes and unregister when it pauses.

@Override
public void onResume() {
    super.onResume();
    IntentFilter filter = new IntentFilter(Intent.ACTION_HEADSET_PLUG);
    this.registerReceiver(mPluginReceiver, filter);
}

@Override
public void onPause() {
    this.unregisterReceiver(mPluginReceiver);
    super.onPause();
}

Internal Notes

• Oboe Issues
  • #381 Connecting headphones does not trigger any event. S9
  • #893 onErrorBeforeClose and onErrorAfterClose not called, S10
  • #908 Huawei MAR-LX3A
  • #1350 SM-G977B fails "Test Disconnects"
• This issue is tracked internally as b/111711159.
• A fix in AOSP is here
• A fix was also merged into pi-dev on July 30, 2018.

Results from Test Disconnect in OboeTester

Device	Build	Result
Pixel 1	QQ1A.190919.002	ALL PASS
Samsung S10e	PPR1.180610.011	MMAP Output plugIN failed
Huawei MAR-LX3A	10.0.0.216	MMAP In/Out fails, Legacy In fails.