Allow volume control to adjust playback volume

The AudioTrack for playing audio from the child device
was sending audio to the voice call stream. It is more
appropriate to use the music stream. In addition, suggest
that the activity control the music stream's volume with
the hardware controls.

src/protect/babymonitor/ListenActivity.java

@@ -50,7 +50,7 @@ public class ListenActivity extends Activity
         int audioEncoding = AudioFormat.ENCODING_PCM_16BIT;
         int bufferSize = AudioTrack.getMinBufferSize(frequency, channelConfiguration, audioEncoding);
 
-        final AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_VOICE_CALL,
+        final AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                 frequency,
                 channelConfiguration,
                 audioEncoding,
@@ -63,6 +63,8 @@ public class ListenActivity extends Activity
         Thread playThread = new Thread(audioPlayer);
         playThread.start();
 
+        setVolumeControlStream(AudioManager.STREAM_MUSIC);
+
         InputStream is = socket.getInputStream();
         int read = 0;