Audio gain conrol To increase the amplitude of the audio u need to calculate the gain factor and multiply calculated gain factor with every sample captured. The following code does that. P.S. Ignore the unrelated code
public class MainActivity extends Activity {
public static final int SAMPLE_RATE = 16000;
private AudioRecord mRecorder; private File mRecording; private short[] mBuffer; private final String startRecordingLabel = "Start recording"; private final String stopRecordingLabel = "Stop recording"; private boolean mIsRecording = false; private ProgressBar mProgressBar; float iGain = 1.0f; CheckBox gain;
protected int bitsPerSamples = 16;
@Override public void onCreate(final Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.fragment_main);
initRecorder();
Button bluetooth = (Button)findViewById(R.id.blue); gain = (CheckBox) findViewById(R.id.checkBox1); mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
final Button button = (Button) findViewById(R.id.start); button.setText(startRecordingLabel);
bluetooth.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub Intent i = new Intent(""); } }); gain.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (gain.isChecked()) { iGain = 5.0f;
} else { iGain = 2.0f; } } });
button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(final View v) { if (!mIsRecording) { button.setText(stopRecordingLabel); mIsRecording = true; mRecorder.startRecording(); mRecording = getFile("raw"); startBufferedWrite(mRecording); } else { button.setText(startRecordingLabel); mIsRecording = false; mRecorder.stop(); File waveFile = getFile("wav"); try { rawToWave(mRecording, waveFile); } catch (IOException e) { Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show(); } Toast.makeText(MainActivity.this, "Recorded to " + waveFile.getName(), Toast.LENGTH_SHORT).show(); } } }); }
@Override public void onDestroy() { mRecorder.release(); super.onDestroy(); }
private void initRecorder() { int bufferSize = AudioRecord.getMinBufferSize(SAMPLE_RATE, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT); mBuffer = new short[bufferSize]; mRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC, SAMPLE_RATE, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, bufferSize); }
private void startBufferedWrite(final File file) { new Thread(new Runnable() { @Override public void run() { DataOutputStream output = null; try { output = new DataOutputStream(new BufferedOutputStream( new FileOutputStream(file))); while (mIsRecording) { double sum = 0;
int readSize = mRecorder.read(mBuffer, 0, mBuffer.length);
final int bytesPerSample = bitsPerSamples / 8; final int emptySpace = 64 - bitsPerSamples; int byteIndex = 0; int byteIndex2 = 0; int temp = 0; int mLeftTemp = 0; int mRightTemp = 0; int a = 0; int x = 0;
for (int frameIndex = 0; frameIndex < readSize; frameIndex++) {
for (int c = 0; c < 1; c++) {
if (iGain != 1) {
long accumulator = 0; for (int b = 0; b < bytesPerSample; b++) {
accumulator += ((long) (mBuffer[byteIndex++] & 0xFF)) << (b * 8 + emptySpace); }
double sample = ((double) accumulator / (double) Long.MAX_VALUE); sample *= iGain; int intValue = (int) ((double) sample * (double) Integer.MAX_VALUE);
for (int i = 0; i < bytesPerSample; i++) { mBuffer[i + byteIndex2] = (byte) (intValue >>> ((i + 2) * 8) & 0xff); } byteIndex2 += bytesPerSample;
} }// end for(channel)
// mBuffer[frameIndex] *=iGain; if (mBuffer[frameIndex] > 32765) { mBuffer[frameIndex] = 32767;
} else if (mBuffer[frameIndex] < -32767) { mBuffer[frameIndex] = -32767; } output.writeShort(mBuffer[frameIndex]); sum += mBuffer[frameIndex] * mBuffer[frameIndex];
}
if (readSize > 0) { final double amplitude = sum / readSize; mProgressBar.setProgress((int) Math.sqrt(amplitude)); } } } catch (IOException e) { Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show(); } finally { mProgressBar.setProgress(0); if (output != null) { try { output.flush(); } catch (IOException e) { Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show(); } finally { try { output.close(); } catch (IOException e) { Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show(); } } } } } }).start(); }
private void rawToWave(final File rawFile, final File waveFile) throws IOException {
byte[] rawData = new byte[(int) rawFile.length()]; DataInputStream input = null; try {
input = new DataInputStream(new FileInputStream(rawFile)); input.read(rawData); } finally { if (input != null) { input.close(); } }
DataOutputStream output = null; try { output = new DataOutputStream(new FileOutputStream(waveFile)); // WAVE header // see http://ccrma.stanford.edu/courses/422/projects/WaveFormat/ writeString(output, "RIFF"); // chunk id writeInt(output, 36 + rawData.length); // chunk size writeString(output, "WAVE"); // format writeString(output, "fmt "); // subchunk 1 id writeInt(output, 16); // subchunk 1 size writeShort(output, (short) 1); // audio format (1 = PCM) writeShort(output, (short) 1); // number of channels writeInt(output, SAMPLE_RATE); // sample rate writeInt(output, SAMPLE_RATE * 2); // byte rate writeShort(output, (short) 2); // block align writeShort(output, (short) 16); // bits per sample writeString(output, "data"); // subchunk 2 id writeInt(output, rawData.length); // subchunk 2 size // Audio data (conversion big endian -> little endian) short[] shorts = new short[rawData.length / 2]; ByteBuffer.wrap(rawData).order(ByteOrder.LITTLE_ENDIAN) .asShortBuffer().get(shorts); ByteBuffer bytes = ByteBuffer.allocate(shorts.length * 2);
for (short s : shorts) {
// Apply Gain /* * s *= iGain; if(s>32767) { s=32767; } else if(s<-32768) { * s=-32768; } */ bytes.putShort(s); } output.write(bytes.array()); } finally { if (output != null) { output.close(); } } }
private File getFile(final String suffix) { Time time = new Time(); time.setToNow(); return new File(Environment.getExternalStorageDirectory(), time.format("%Y%m%d%H%M%S") + "." + suffix); }
private void writeInt(final DataOutputStream output, final int value) throws IOException { output.write(value >> 0); output.write(value >> 8); output.write(value >> 16); output.write(value >> 24); }
private void writeShort(final DataOutputStream output, final short value) throws IOException { output.write(value >> 0); output.write(value >> 8); }
private void writeString(final DataOutputStream output, final String value) throws IOException { for (int i = 0; i < value.length(); i++) { output.write(value.charAt(i)); } } }

Audio gain conrol To increase the amplitude of the audio u need to calculate the gain factor and multiply calculated gain factor with every sample captured. The following code does that. P.S. Ignore the unrelated code

public class MainActivity extends Activity {
public static final int SAMPLE_RATE = 16000;
private AudioRecord mRecorder; private File mRecording; private short[] mBuffer; private final String startRecordingLabel = "Start recording"; private final String stopRecordingLabel = "Stop recording"; private boolean mIsRecording = false; private ProgressBar mProgressBar; float iGain = 1.0f; CheckBox gain;
protected int bitsPerSamples = 16;
@Override public void onCreate(final Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.fragment_main);
initRecorder();
Button bluetooth = (Button)findViewById(R.id.blue); gain = (CheckBox) findViewById(R.id.checkBox1); mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
final Button button = (Button) findViewById(R.id.start); button.setText(startRecordingLabel);
bluetooth.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub Intent i = new Intent(""); } }); gain.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (gain.isChecked()) { iGain = 5.0f;
} else { iGain = 2.0f; } } });
button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(final View v) { if (!mIsRecording) { button.setText(stopRecordingLabel); mIsRecording = true; mRecorder.startRecording(); mRecording = getFile("raw"); startBufferedWrite(mRecording); } else { button.setText(startRecordingLabel); mIsRecording = false; mRecorder.stop(); File waveFile = getFile("wav"); try { rawToWave(mRecording, waveFile); } catch (IOException e) { Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show(); } Toast.makeText(MainActivity.this, "Recorded to " + waveFile.getName(), Toast.LENGTH_SHORT).show(); } } }); }
@Override public void onDestroy() { mRecorder.release(); super.onDestroy(); }
private void initRecorder() { int bufferSize = AudioRecord.getMinBufferSize(SAMPLE_RATE, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT); mBuffer = new short[bufferSize]; mRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC, SAMPLE_RATE, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, bufferSize); }
private void startBufferedWrite(final File file) { new Thread(new Runnable() { @Override public void run() { DataOutputStream output = null; try { output = new DataOutputStream(new BufferedOutputStream( new FileOutputStream(file))); while (mIsRecording) { double sum = 0;
int readSize = mRecorder.read(mBuffer, 0, mBuffer.length);
final int bytesPerSample = bitsPerSamples / 8; final int emptySpace = 64 - bitsPerSamples; int byteIndex = 0; int byteIndex2 = 0; int temp = 0; int mLeftTemp = 0; int mRightTemp = 0; int a = 0; int x = 0;
for (int frameIndex = 0; frameIndex < readSize; frameIndex++) {
for (int c = 0; c < 1; c++) {
if (iGain != 1) {
long accumulator = 0; for (int b = 0; b < bytesPerSample; b++) {
accumulator += ((long) (mBuffer[byteIndex++] & 0xFF)) << (b * 8 + emptySpace); }
double sample = ((double) accumulator / (double) Long.MAX_VALUE); sample *= iGain; int intValue = (int) ((double) sample * (double) Integer.MAX_VALUE);
for (int i = 0; i < bytesPerSample; i++) { mBuffer[i + byteIndex2] = (byte) (intValue >>> ((i + 2) * 8) & 0xff); } byteIndex2 += bytesPerSample;
} }// end for(channel)
// mBuffer[frameIndex] *=iGain; if (mBuffer[frameIndex] > 32765) { mBuffer[frameIndex] = 32767;
} else if (mBuffer[frameIndex] < -32767) { mBuffer[frameIndex] = -32767; } output.writeShort(mBuffer[frameIndex]); sum += mBuffer[frameIndex] * mBuffer[frameIndex];
}
if (readSize > 0) { final double amplitude = sum / readSize; mProgressBar.setProgress((int) Math.sqrt(amplitude)); } } } catch (IOException e) { Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show(); } finally { mProgressBar.setProgress(0); if (output != null) { try { output.flush(); } catch (IOException e) { Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show(); } finally { try { output.close(); } catch (IOException e) { Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show(); } } } } } }).start(); }
private void rawToWave(final File rawFile, final File waveFile) throws IOException {
byte[] rawData = new byte[(int) rawFile.length()]; DataInputStream input = null; try {
input = new DataInputStream(new FileInputStream(rawFile)); input.read(rawData); } finally { if (input != null) { input.close(); } }
DataOutputStream output = null; try { output = new DataOutputStream(new FileOutputStream(waveFile)); // WAVE header // see http://ccrma.stanford.edu/courses/422/projects/WaveFormat/ writeString(output, "RIFF"); // chunk id writeInt(output, 36 + rawData.length); // chunk size writeString(output, "WAVE"); // format writeString(output, "fmt "); // subchunk 1 id writeInt(output, 16); // subchunk 1 size writeShort(output, (short) 1); // audio format (1 = PCM) writeShort(output, (short) 1); // number of channels writeInt(output, SAMPLE_RATE); // sample rate writeInt(output, SAMPLE_RATE * 2); // byte rate writeShort(output, (short) 2); // block align writeShort(output, (short) 16); // bits per sample writeString(output, "data"); // subchunk 2 id writeInt(output, rawData.length); // subchunk 2 size // Audio data (conversion big endian -> little endian) short[] shorts = new short[rawData.length / 2]; ByteBuffer.wrap(rawData).order(ByteOrder.LITTLE_ENDIAN) .asShortBuffer().get(shorts); ByteBuffer bytes = ByteBuffer.allocate(shorts.length * 2);
for (short s : shorts) {
// Apply Gain /* * s *= iGain; if(s>32767) { s=32767; } else if(s<-32768) { * s=-32768; } */ bytes.putShort(s); } output.write(bytes.array()); } finally { if (output != null) { output.close(); } } }
private File getFile(final String suffix) { Time time = new Time(); time.setToNow(); return new File(Environment.getExternalStorageDirectory(), time.format("%Y%m%d%H%M%S") + "." + suffix); }
private void writeInt(final DataOutputStream output, final int value) throws IOException { output.write(value >> 0); output.write(value >> 8); output.write(value >> 16); output.write(value >> 24); }
private void writeShort(final DataOutputStream output, final short value) throws IOException { output.write(value >> 0); output.write(value >> 8); }
private void writeString(final DataOutputStream output, final String value) throws IOException { for (int i = 0; i < value.length(); i++) { output.write(value.charAt(i)); } } }