android - TTS output always going to A2DP

Question

My Android tutorial states that I can explicitly tell the TTS engine which stream to use:

For music playback:

params.put(TextToSpeech.Engine.KEY_PARAM_STREAM, String.valueOf(AudioManager.STREAM_MUSIC));

And for phone calls:

params.put(TextToSpeech.Engine.KEY_PARAM_STREAM, String.valueOf(AudioManager.STREAM_VOICE_CALL));

My understanding is that audio routing to a Bluetooth headset works such that STREAM_MUSIC goes to A2DP (aka "media audio" in Android Bluetooth settings) and STREAM_VOICE_CALL goes to HSP (aka "phone audio" in Android Bluetooth settings).

But regardless whether I use STREAM_MUSIC or STREAM_VOICE_CALL in my little application, the audio always goes for some reason to A2DP.

What am I am doing wrong? Is there a way to route TTS output to headset's HSP profile?

Answer 1

I got this working for the most part, on most devices. Here is the part that starts the TTS on the voice call stream using Bluetooth SCO instead of A2DP.

if (mTtsReady) {
    myHash = new HashMap<String, String>();

    myHash.put(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID, "A2DP_Vol");

    OLD_AUDIO_MODE = am2.getMode();
    if(SMSstream == 1){
        if (am2.isBluetoothScoAvailableOffCall()) {
            am2.startBluetoothSco();
        }
        if(!am2.isSpeakerphoneOn()){
            speakerPhoneWasOn = false;
            am2.setSpeakerphoneOn(true);
        }
        myHash.put(TextToSpeech.Engine.KEY_PARAM_STREAM,
                String.valueOf(AudioManager.STREAM_VOICE_CALL));
        am2.requestAudioFocus(null, AudioManager.STREAM_VOICE_CALL,
                AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);

    }
    else{
        am2.requestAudioFocus(null, AudioManager.STREAM_MUSIC,
        AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
        myHash.put(TextToSpeech.Engine.KEY_PARAM_STREAM,
                String.valueOf(AudioManager.STREAM_MUSIC));
    }

    new CountDownTimer(SMS_DELAY, SMS_DELAY/2) {

        @Override
        public void onFinish() {
            try {
                mTts.speak(str, TextToSpeech.QUEUE_ADD,
                        myHash);
            } catch (Exception e) {
                Toast.makeText(application,
                        R.string.TTSNotReady,
                        Toast.LENGTH_LONG).show();
                e.printStackTrace();
            }

        }

        @Override
        public void onTick(long arg0) {

        }

    }.start();
}

Now I just have a problem getting the stream to revert back when done. It all works fine to read TTS. It will pause any music, play the TTS, and then resume music fine. However, when I exit the app later the stream for media now plays through the phone earpiece until I reboot. I posted that question here: Audio stream stays on earpiece after using AudioManager

You can see my whole project here: http://code.google.com/p/a2dpvolume/