Pause function in Audio Recorder

Question

I want to implement pause and resume functionality to my Audio Recorder. I know I cant use MediaRecorder to do this. So please give me the source code of a class which can join two AAC audio file.

Answer 1

MediaRecorder added pause functionality from API level 24. If your minSdkVersion is less than 24, you can use the code below. It is extracted from this page. It generates a wave file in the given name after the recording is stopped.

import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;

public class RecordAudio extends AppCompatActivity {

    private static final int RECORDER_BPP = 16;
    private static final int RECORDER_SAMPLE_RATE = 8000;
    private static final int RECORDER_CHANNELS = AudioFormat.CHANNEL_IN_STEREO;
    private static final int RECORDER_AUDIO_ENCODING = AudioFormat.ENCODING_PCM_16BIT;

    private Button recordButton, stopButton, pauseButton, resumeButton;
    private EditText recordingName;
    private AudioRecord recorder = null;
    private int bufferSize = 0;
    private Thread recordingThread = null;
    private boolean isRecording = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_record_audio);

        bufferSize = AudioRecord.getMinBufferSize(RECORDER_SAMPLE_RATE, RECORDER_CHANNELS, RECORDER_AUDIO_ENCODING);
        recordButton = (Button) findViewById(R.id.record_button);
        stopButton = (Button) findViewById(R.id.stop_button);
        pauseButton = (Button) findViewById(R.id.pause_button);
        resumeButton = (Button) findViewById(R.id.resume_button);
        recordingName = (EditText) findViewById(R.id.recording_name);

        recordButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startRecording(false);
            }
        });

        pauseButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                stopRecording(false);
            }
        });

        resumeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startRecording(true);
            }
        });

        stopButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                stopRecording(true);
            }
        });
    }

    private void startRecording(final boolean b) {
        recorder = new AudioRecord(MediaRecorder.AudioSource.MIC, RECORDER_SAMPLE_RATE, RECORDER_CHANNELS, RECORDER_AUDIO_ENCODING, bufferSize);
        recorder.startRecording();
        isRecording = true;
        recordingThread = new Thread(new Runnable() {
            @Override
            public void run() {
                writeAudioDataToFile(b);
            }
        }, "AudioRecorder Thread");
        recordingThread.start();
    }

    private void writeAudioDataToFile(boolean b) {
        byte data[] = new byte[bufferSize];
        String filename = getTempFilename();
        FileOutputStream os = null;

        try {
            os = new FileOutputStream(filename, b);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        int read = 0;

        if (os != null) {
            while (isRecording) {
                read = recorder.read(data, 0, bufferSize);

                if (AudioRecord.ERROR_INVALID_OPERATION != read) {
                    try {
                        os.write(data);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }

            try {
                os.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private String getTempFilename() {
        String filepath = Environment.getExternalStorageDirectory().getPath();
        File file = new File(filepath + "/recording_temp.raw");
        try {
            file.createNewFile();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return (file.getAbsolutePath());
    }

    private void stopRecording(boolean b) {
        if (recorder != null) {
            isRecording = false;

            recorder.stop();
            recorder.release();

            recorder = null;
            recordingThread = null;
        }

        if (b == true) {
            copyWaveFile(getTempFilename(), getFilename());
            deleteTempFile();
        }
    }

    private void copyWaveFile(String inFilename, String outFilename) {
        FileInputStream in = null;
        FileOutputStream out = null;
        long totalAudioLen = 0;
        long totalDataLen = totalAudioLen + 44;
        long longSampleRate = RECORDER_SAMPLE_RATE;
        int channels = 2;
        long byteRate = RECORDER_BPP * RECORDER_SAMPLE_RATE * channels / 8;

        byte[] data = new byte[bufferSize];

        try {
            in = new FileInputStream(inFilename);
            out = new FileOutputStream(outFilename, true);
            totalAudioLen = in.getChannel().size() + out.getChannel().size();
            totalDataLen = totalAudioLen + 44;

            WriteWaveFileHeader(out, totalAudioLen, totalDataLen,
                    longSampleRate, channels, byteRate, outFilename);

            while (in.read(data) != -1) {
                out.write(data);
            }

            in.close();
            out.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void WriteWaveFileHeader(
            FileOutputStream out, long totalAudioLen,
            long totalDataLen, long longSampleRate, int channels,
            long byteRate, String outFileName) throws IOException {

        byte[] header = new byte[44];

        header[0] = 'R';  // RIFF/WAVE header
        header[1] = 'I';
        header[2] = 'F';
        header[3] = 'F';
        header[4] = (byte) (totalDataLen & 0xff);
        header[5] = (byte) ((totalDataLen >> 8) & 0xff);
        header[6] = (byte) ((totalDataLen >> 16) & 0xff);
        header[7] = (byte) ((totalDataLen >> 24) & 0xff);
        header[8] = 'W';
        header[9] = 'A';
        header[10] = 'V';
        header[11] = 'E';
        header[12] = 'f';  // 'fmt ' chunk
        header[13] = 'm';
        header[14] = 't';
        header[15] = ' ';
        header[16] = 16;  // 4 bytes: size of 'fmt ' chunk
        header[17] = 0;
        header[18] = 0;
        header[19] = 0;
        header[20] = 1;  // format = 1
        header[21] = 0;
        header[22] = (byte) channels;
        header[23] = 0;
        header[24] = (byte) (longSampleRate & 0xff);
        header[25] = (byte) ((longSampleRate >> 8) & 0xff);
        header[26] = (byte) ((longSampleRate >> 16) & 0xff);
        header[27] = (byte) ((longSampleRate >> 24) & 0xff);
        header[28] = (byte) (byteRate & 0xff);
        header[29] = (byte) ((byteRate >> 8) & 0xff);
        header[30] = (byte) ((byteRate >> 16) & 0xff);
        header[31] = (byte) ((byteRate >> 24) & 0xff);
        header[32] = (byte) (2 * 16 / 8);  // block align
        header[33] = 0;
        header[34] = RECORDER_BPP;  // bits per sample
        header[35] = 0;
        header[36] = 'd';
        header[37] = 'a';
        header[38] = 't';
        header[39] = 'a';
        header[40] = (byte) (totalAudioLen & 0xff);
        header[41] = (byte) ((totalAudioLen >> 8) & 0xff);
        header[42] = (byte) ((totalAudioLen >> 16) & 0xff);
        header[43] = (byte) ((totalAudioLen >> 24) & 0xff);

        RandomAccessFile rFile = new RandomAccessFile(outFileName, "rw");
        rFile.seek(0);
        rFile.write(header, 0, 44);
        rFile.close();
    }

    private String getFilename() {
        String filepath = Environment.getExternalStorageDirectory().getPath();
        File file = new File(filepath + "/record_" + recordingName.getText() + ".wav");
        try {
            file.createNewFile();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return (file.getAbsolutePath());
    }

    private void deleteTempFile() {
        File file = new File(getTempFilename());
        file.delete();
    }
}