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MediaRecorder

The Android multimedia framework includes support for capturing and encoding a variety of common audio and video formats. You can use the MediaRecorder APIs if supported by the device hardware.

This document shows you how to use MediaRecorder to write an application that captures audio from a device microphone, save the audio, and play it back (with MediaPlayer). To record video you'll need to use the device's camera along with MediaRecorder. This is described in the Camera guide.

Note: The Android Emulator cannot record audio. Be sure to test your code on a real device that can record.

Requesting permission to record audio

To be able to record, your app must tell the user that it will access the device's audio input. You must include this permission tag in the app's manifest file:

<uses-permission android:name="android.permission.RECORD_AUDIO" />

RECORD_AUDIO is considered a "dangerous" permission because it may pose a risk to the user's privacy. Starting with Android 6.0 (API level 23) an app that uses a dangerous permission must ask the user for approval at run time. After the user has granted permission, the app should remember and not ask again. The sample code below shows how to implement this behavior using ActivityCompat.requestPermissions().

Creating and running a MediaRecorder

Initialize a new instance of MediaRecorder with the following calls:

Start and stop the recorder by calling start() and stop() respectively.

When you are done with the MediaRecorder instance free its resources as soon as possible by calling release().

Using MediaMuxer to record multiple channels

Starting with Android 8.0 (API level 26) you can use a MediaMuxer to record multiple simultaneous audio and video streams. In earlier versions of Android you can only record one audio track and/or one video track at a time.

Use the addTrack() method to mix multipe tracks together.

You can also add one or more metadata tracks with custom information for each frame, but only to MP4 containers. Your app defines the format and content of the metadata.

Adding metadata

Metadata can be useful for offline processing. For example, data captured from the gyro sensor could be used to perform video stabilization.

When you add a metadata track, the track's mime format must start with the prefix application/. Writing metadata is the same as writing video or audio data, except that the data does not come from a MediaCodec. Instead, the app passes a ByteBuffer with an associated timestamp to the writeSampleData() method. The timestamp must be in the same time base as the video and audio tracks.

The generated MP4 file uses the TextMetaDataSampleEntry defined in section 12.3.3.2 of the ISO BMFF specification to signal the metadata's mime format. When you use a MediaExtractor to extract a file that contains metadata tracks, the metadata's mime format appears as an instance of MediaFormat.

Sample code

The example activity below shows how to use MediaRecorder to record an audio file. It Also uses MediaPlayer to play the audio back.

package com.android.audiorecordtest;

import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.media.MediaPlayer;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.LinearLayout;

import java.io.IOException;

public class AudioRecordTest extends AppCompatActivity {

    private static final String LOG_TAG = "AudioRecordTest";
    private static final int REQUEST_RECORD_AUDIO_PERMISSION = 200;
    private static String mFileName = null;

    private RecordButton mRecordButton = null;
    private MediaRecorder mRecorder = null;

    private PlayButton   mPlayButton = null;
    private MediaPlayer   mPlayer = null;

    // Requesting permission to RECORD_AUDIO
    private boolean permissionToRecordAccepted = false;
    private String [] permissions = {Manifest.permission.RECORD_AUDIO};

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode){
            case REQUEST_RECORD_AUDIO_PERMISSION:
                permissionToRecordAccepted  = grantResults[0] == PackageManager.PERMISSION_GRANTED;
                break;
        }
        if (!permissionToRecordAccepted ) finish();

    }

    private void onRecord(boolean start) {
        if (start) {
            startRecording();
        } else {
            stopRecording();
        }
    }

    private void onPlay(boolean start) {
        if (start) {
            startPlaying();
        } else {
            stopPlaying();
        }
    }

    private void startPlaying() {
        mPlayer = new MediaPlayer();
        try {
            mPlayer.setDataSource(mFileName);
            mPlayer.prepare();
            mPlayer.start();
        } catch (IOException e) {
            Log.e(LOG_TAG, "prepare() failed");
        }
    }

    private void stopPlaying() {
        mPlayer.release();
        mPlayer = null;
    }

    private void startRecording() {
        mRecorder = new MediaRecorder();
        mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mRecorder.setOutputFile(mFileName);
        mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);

        try {
            mRecorder.prepare();
        } catch (IOException e) {
            Log.e(LOG_TAG, "prepare() failed");
        }

        mRecorder.start();
    }

    private void stopRecording() {
        mRecorder.stop();
        mRecorder.release();
        mRecorder = null;
    }

    class RecordButton extends Button {
        boolean mStartRecording = true;

        OnClickListener clicker = new OnClickListener() {
            public void onClick(View v) {
                onRecord(mStartRecording);
                if (mStartRecording) {
                    setText("Stop recording");
                } else {
                    setText("Start recording");
                }
                mStartRecording = !mStartRecording;
            }
        };

        public RecordButton(Context ctx) {
            super(ctx);
            setText("Start recording");
            setOnClickListener(clicker);
        }
    }

    class PlayButton extends Button {
        boolean mStartPlaying = true;

        OnClickListener clicker = new OnClickListener() {
            public void onClick(View v) {
                onPlay(mStartPlaying);
                if (mStartPlaying) {
                    setText("Stop playing");
                } else {
                    setText("Start playing");
                }
                mStartPlaying = !mStartPlaying;
            }
        };

        public PlayButton(Context ctx) {
            super(ctx);
            setText("Start playing");
            setOnClickListener(clicker);
        }
    }

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        // Record to the external cache directory for visibility
        mFileName = getExternalCacheDir().getAbsolutePath();
        mFileName += "/audiorecordtest.3gp";

        ActivityCompat.requestPermissions(this, permissions, REQUEST_RECORD_AUDIO_PERMISSION);

        LinearLayout ll = new LinearLayout(this);
        mRecordButton = new RecordButton(this);
        ll.addView(mRecordButton,
                new LinearLayout.LayoutParams(
                        ViewGroup.LayoutParams.WRAP_CONTENT,
                        ViewGroup.LayoutParams.WRAP_CONTENT,
                        0));
        mPlayButton = new PlayButton(this);
        ll.addView(mPlayButton,
                new LinearLayout.LayoutParams(
                        ViewGroup.LayoutParams.WRAP_CONTENT,
                        ViewGroup.LayoutParams.WRAP_CONTENT,
                        0));
        setContentView(ll);
    }

    @Override
    public void onStop() {
        super.onStop();
        if (mRecorder != null) {
            mRecorder.release();
            mRecorder = null;
        }

        if (mPlayer != null) {
            mPlayer.release();
            mPlayer = null;
        }
    }
}

Note: The android-MediaRecorder sample further demonstrates the use of the APIs covered on this page.

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