我正在努力增加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？能帮帮我吧。
答案 0 :(得分：1)
this link应该会带给你更多。使用setStreamVolume（...）将音量设置得更高。但请注意，通过调用getStreamMaxVolume（...）可以获得最大值。所以麦克风增益可能受到我猜的硬件限制。所以不可能“在飞行中”这样做，但是记录一下，尝试通过equalizer放大一个特殊频率然后识别像心跳这样的东西呢？听起来很难但也许可能。
答案 1 :(得分：0)
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));
}
}
}