Android Wear Audio Recorder using ChannelAPI
I am trying to create an audio recording app for Android Wear. Right now, I can capture the sound on the watch, transfer it to my phone, and save it to a file. However, there are gaps or cut-offs in the audio file.
I found these asked questions related to my link1 , link2 problem , but they couldn't help me.
Here is my code:
Firstly, from the time zone side, I create a channel using channelAPI and successfully send the audio recorded on the watch to the smartphone.
//here are the variables values that I used
//44100Hz is currently the only rate that is guaranteed to work on all devices
//but other rates such as 22050, 16000, and 11025 may work on some devices.
private static final int RECORDER_SAMPLE_RATE = 44100;
private static final int RECORDER_CHANNELS = AudioFormat.CHANNEL_IN_MONO;
private static final int RECORDER_AUDIO_ENCODING = AudioFormat.ENCODING_PCM_16BIT;
int BufferElements2Rec = 1024;
int BytesPerElement = 2;
//start the process of recording audio
private void startRecording() {
recorder = new AudioRecord(MediaRecorder.AudioSource.MIC,
RECORDER_SAMPLE_RATE, RECORDER_CHANNELS,
RECORDER_AUDIO_ENCODING, BufferElements2Rec * BytesPerElement);
recorder.startRecording();
isRecording = true;
recordingThread = new Thread(new Runnable() {
public void run() {
writeAudioDataToPhone();
}
}, "AudioRecorder Thread");
recordingThread.start();
}
private void writeAudioDataToPhone(){
short sData[] = new short[BufferElements2Rec];
ChannelApi.OpenChannelResult result = Wearable.ChannelApi.openChannel(googleClient, nodeId, "/mypath").await();
channel = result.getChannel();
Channel.GetOutputStreamResult getOutputStreamResult = channel.getOutputStream(googleClient).await();
OutputStream outputStream = getOutputStreamResult.getOutputStream();
while (isRecording) {
// gets the voice output from microphone to byte format
recorder.read(sData, 0, BufferElements2Rec);
try {
byte bData[] = short2byte(sData);
outputStream.write(bData);
} catch (IOException e) {
e.printStackTrace();
}
}
try {
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Then, from the smartphone side, I get the audio data from the channel and write it to a PCM file.
public void onChannelOpened(Channel channel) {
if (channel.getPath().equals("/mypath")) {
Channel.GetInputStreamResult getInputStreamResult = channel.getInputStream(mGoogleApiClient).await();
inputStream = getInputStreamResult.getInputStream();
writePCMToFile(inputStream);
MainActivity.this.runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(MainActivity.this, "Audio file received!", Toast.LENGTH_SHORT).show();
}
});
}
}
public void writePCMToFile(InputStream inputStream) {
OutputStream outputStream = null;
try {
// write the inputStream to a FileOutputStream
outputStream = new FileOutputStream(new File("/sdcard/wearRecord.pcm"));
int read = 0;
byte[] bytes = new byte[1024];
while ((read = inputStream.read(bytes)) != -1) {
outputStream.write(bytes, 0, read);
}
System.out.println("Done writing PCM to file!");
} catch (Exception e) {
e.printStackTrace();
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (Exception e) {
e.printStackTrace();
}
}
if (outputStream != null) {
try {
// outputStream.flush();
outputStream.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
What am I doing wrong or your suggestions for creating the perfect silent audio file on your smartphone? Thanks in advance.
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I noticed in your code that you are all reading into a short [] array and then converting it to a byte [] array for the send feed API. Your code also creates a new byte [] array through each iteration of the loop, which will create a lot of work for the garbage collector. In general, you want to avoid allocation within loops.
I would allocate a single byte [] array at the top and let the AudioRecord class store it directly in a byte [] array (just make sure you allocate twice as many bytes as you did shorts), with code like this:
mAudioTemp = new byte[bufferSize];
int result;
while ((result = mAudioRecord.read(mAudioTemp, 0, mAudioTemp.length)) > 0) {
try {
mAudioStream.write(mAudioTemp, 0, result);
} catch (IOException e) {
Log.e(Const.TAG, "Write to audio channel failed: " + e);
}
}
I also tested this with a 1 second sound buffer using code like this and it worked well. I don't know what the minimum buffer size is before it starts to experience problems:
int bufferSize = Math.max(
AudioTrack.getMinBufferSize(44100, AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT),
44100 * 2);
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