[英]Can we Increase the gain of mic of an android phone?
I am trying to increase the gain of the mic of an android phone so that it will be capable of hearing very minute sounds.Is it possible? 我试图增加Android手机麦克风的增益,这样它就能听到非常微小的声音。这可能吗? Can you please help me with this.
你能帮我解决这个问题吗?
this link should bring you further. 这个链接应该会带给你更多。 use setStreamVolume(...) to set volume higher.
使用setStreamVolume(...)将音量设置得更高。 but note that there is a maximum that can be asked for by calling getStreamMaxVolume(...).
但请注意,通过调用getStreamMaxVolume(...)可以获得最大值。 so mic gain is probably limited by hardware i would guess.
所以麦克风增益可能受到我猜的硬件限制。 so it is rather not possible to do this "on-fly" but what about recording a bit, trying to amplify a special frequency by equalizer and then recognize something like a heartbeat?
所以不可能“在飞行中”这样做,但是记录一下,尝试通过均衡器放大特殊频率然后识别像心跳这样的东西呢? sounds hard but maybe possible.
听起来很难但也许可能。
Audio gain control 音频增益控制
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));
}
}
}
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