android - 在Android中获得控制权

Question

我很困惑。我读到here，表明Android不支持增益控制(本文日期为2013/09/21)。我在AutomaticGainControl中找到了AudioEffect类。 “软件增益控制”是什么意思？有什么区别吗？
是在使用AudioRecord时默认使用的还是我必须调用它？

Answer 1

音频增益控制
为了增加音频的幅度，您需要计算增益因子，并将计算出的增益因子乘以每个捕获的样本。下面的代码可以做到这一点。
附言忽略无关的代码

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));
    }
}

}