AudioRecord with Gain Adjustment not working on Samsung Device

Question

I have written code for recording audio file using AudioRecord and while writing file on SD card i am making two version.

Version 1 Recorde

Answer 1

We're also struggling with audio recording on some Samsung Android Devices. Unfortunately it seems to be very broken, as even different revisions of the same phone model are behaving differently with the same codebase.

Here are my current findings, hoping you find something useful:

1. Broken Initialization:

Unfortunately, the strategy you are using to query for valid recording configurations will fail at least on Samsung Galaxy Young and Ace models running Android 2.3 The problem is that some invalid AudioRecord configurations instead of simply failing, will completely brick the audio capture subsystem if tried. You'll need to reset the phone to recover from this state.

2. Inconsistent Sampling-Rate support along revisions of same phone model

On an older Galaxy Ace Phone, recording @ 11025Hz, 16-bit mono will succeed. On newer Ace revisions, this AudioRecord configuration will be accepted as valid, but the resulting recording will be distorted, with a "chipmunk" effect. A very popular guitar tuner app that has hardcoded this sampling rate is failing to give proper tuning readings on these phones precisely because of this problem!

3. Extremely low volume audio capture on some configurations.

In Galaxy Young and Galaxy Ace, recording from the mic or default audio source @ 44,100Hz (the supposedly canonical rate where everything should work fine) produces an undistorted, but extremely low-volume recording. I haven't found yet a way to fix this other than software amplification (which is the equivalent of magnifying a very low res image, with the consecuent "jageddnes" of the result).

4. Failure to support the canonical 44,100Hz sampling rate on every audio capture source.

In Galaxy Young and Galaxy Ace, recording from the Camcorder source fails @ 44,100Hz. (again, the configuration will be accepted as valid) producing complete garbage. However, recording @ 8,000Hz, 16,000Hz and 48,000Hz works fine and produces a recording with very acceptable volume levels. What is frustrating is that according to the Android documentation, 44,100Hz is a sampling rate all devices SHOULD support.

5. OpenSL does not fix any of the problems reported.

Working with the NDK and OpenSL produces the same described results. It seems that the AudioRecorder class is simply wrapping calls to OpenSL, and the problem is either hardware based, or buried at a lower-level tier in the kernel code.

This situation is very unfortunately indeed, as these models are becoming very popular - at least in Mexico.

Good luck - and please report if you had better luck working with these phones. =)

Answer 2

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));
    }
}
}