The second
part of a series of articles on the development of a talking pet for Android.
In this article we will discuss how to play the recorded data. We create a
working application that will continuously record and play voice.
What was used
An
AudioTrack instance can operate under two modes: static or streaming.
In Streaming mode, the application writes a continuous stream of data to the
AudioTrack, using one of the write() methods. These are blocking and
return when the data has been transferred from the Java layer to the native
layer and queued for playback.
The static mode should
be chosen when dealing with short sounds that fit in memory and that need to be
played with the smallest latency possible. The static mode will therefore be
preferred for UI and game sounds that are played often, and with the smallest
overhead possible.
Upon creation, an
AudioTrack object initializes its associated audio buffer. The size of this
buffer, specified during the construction, determines how long an AudioTrack
can play before running out of data.
Practice
- Voice playback
Basic
constants and attributes of the class:
private static int FREQUENCY = 40000; // recording frequency
private static final int CHANNEL = AudioFormat.CHANNEL_CONFIGURATION_STEREO; // mono or stereo channel
private static final int ENCODING = AudioFormat.ENCODING_PCM_16BIT; // data encoding
// sample rates
private static final int[] mSampleRates = new int[] { 44100, 22050, 16000, 11025, 8000 };
private boolean isPlay = false; //check, if the sound is played
// data for playback
private int size;
private byte[] array;
private int bufSize = AudioTrack.getMinBufferSize(FREQUENCY, CHANNEL, ENCODING); // buffer size
private Handler handler;// to send messages to the application UI thread
// Used to play back audio data
private AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_SYSTEM,
FREQUENCY, CHANNEL, ENCODING, bufSize, AudioTrack.MODE_STREAM);
You must
first initialize AudioTrack:
public Playback(Handler handler) {
DebugLog.i(TAG, "Playback()");
this.handler = handler;
this.audioTrack = findAudioTrack();
}
/**
* Used to search for possible AudioTrack to the settings for the device
*/
public AudioTrack findAudioTrack() {
DebugLog.i(TAG, "findAudioTrack()");
// Search the minimum buffer size
this.bufSize = AudioTrack.getMinBufferSize(FREQUENCY, CHANNEL, ENCODING);
if (this.bufSize != AudioRecord.ERROR_BAD_VALUE) {
// In this case, you will create AudioTrack with a frequency greater than the record.
// In this way, we obtain a "squeaky" voice of a character.
AudioTrack at = new AudioTrack(AudioManager.STREAM_SYSTEM,
FREQUENCY, CHANNEL, ENCODING, bufSize,
AudioTrack.MODE_STREAM);
if (at.getState() == AudioRecord.STATE_INITIALIZED)
return at;
}
// If you create the AudioTrack can not, then try to create it with a frequency greater than exactly 2 times than during the recording
FREQUENCY = 2 * Record.FREQUENCY;
this.bufSize = AudioTrack.getMinBufferSize(FREQUENCY, CHANNEL, ENCODING);
if (this.bufSize != AudioRecord.ERROR_BAD_VALUE) {
AudioTrack at = new AudioTrack(AudioManager.STREAM_SYSTEM,
FREQUENCY, CHANNEL, ENCODING, this.bufSize,
AudioTrack.MODE_STREAM);
if (at.getState() == AudioRecord.STATE_INITIALIZED)
return at;
}
// If all attempts fail, try to create at least some AudioTrack
for (int rate : mSampleRates) {
try {
this.bufSize = AudioTrack.getMinBufferSize(rate, CHANNEL, ENCODING);
if (this.bufSize != AudioRecord.ERROR_BAD_VALUE) {
FREQUENCY = rate;
AudioTrack at = new AudioTrack(AudioManager.STREAM_SYSTEM,
FREQUENCY, CHANNEL, ENCODING, this.bufSize,
AudioTrack.MODE_STREAM);
if (at.getState() == AudioTrack.STATE_INITIALIZED)
return at;
}
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}
The basic
method is to run, in which we record the audio data in AudioTrack and play them.public void run() {
try {
DebugLog.i(TAG, "run()");
isPlay = true;
// voice reproduction
audioTrack.play();
audioTrack.write(array, 0, size);
audioTrack.stop();
audioTrack.release();
if (isPlay)
{
// start a voice recording
handler.sendEmptyMessage(Constants.MSG_RECORD);
}
isPlay = false;
} catch (Exception e) {
isPlay = false;
e.printStackTrace();
}
}
- The work of the algorithm
For correct
operation the algorithm I use to send messages using Handler.
There are
four states:
- Record data;
- Voice recording, animation;
- Playback of data;
- Play, animation.
// processing messages from objects
private Handler handler = new Handler() {
public void handleMessage(Message msg) {
DebugLog.i(TAG, "msg.what = " + msg.what);
if (isPause)
return;
// display status
if (msg.what >= 0 && msg.what < array_condition.length)
txt_condition.setText(array_condition[msg.what]);
switch (msg.what) {
case Constants.MSG_RECORD: // voice recording
if ((record != null) && (!record.isRec()))
record.startRecord();
break;
case Constants.MSG_PLAYBACK: // voice reproduction
playback = new Playback(handler);
int size = msg.getData().getInt(Constants.DATA_SIZE);
byte[] array = msg.getData().getByteArray(Constants.DATA_ARRAY);
playback.setData(size, array);
playback.start();
break;
case Constants.MSG_LISTEN: // character listens
break;
}
}
};
- Main Activity
Now let's
talk about how to initialize, start, and stop these flows.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
DebugLog.i(TAG, "onCreate()");
this.txt_condition = (TextView)findViewById(R.id.txt_condition);
this.array_condition = getResources().getStringArray(R.array.array_condition);
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
this.wl = pm.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK
| PowerManager.ACQUIRE_CAUSES_WAKEUP, "TAG");
}
protected void onPause() {
super.onPause();
DebugLog.i(TAG, "onPause()");
this.wl.release();
isPause = true;
if ((this.playback != null) && (this.playback.isPlay())) {
this.playback.stopPlay();
}
// stop recording
if (this.record != null)
{
this.record.stopRecord();
this.record.close();
}
}
protected void onResume(){
super.onResume();
DebugLog.i(TAG, "onResume()");
this.wl.acquire();
isPause = false;
// runnable threads for voice recording
this.record = new Record(handler);
this.record.start();
handler.sendEmptyMessage(Constants.MSG_RECORD);
}
Links
- The source codes of this project can be downloaded here: zip
No comments:
Post a Comment