Android Java Project to Build MP4 Video to MP3 Audio Converter Using MediaMuxer Class

Welcome folks today in this blog post we will be seeing how to build mp4 video to mp3 audio converter using MediaMuxer class in java. All the full source code of the application is shown below.

Get Started

In order to get started you need to make a new android project inside the android studio and then you will see the below directory structure as shown below at the end of the project.

Now we need to edit the AndroidManifest.xml file and add the necessary permissions for saving the mp3 file inside the external storage and also we need to add the provider tag as well as shown below

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

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

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/Theme.Mp4toMp3Project"
        tools:targetApi="31">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>


        <provider
            android:name="androidx.core.content.FileProvider"
            android:authorities="${applicationId}.provider"
            android:grantUriPermissions="true"
            android:exported="false">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/provider_paths" />
        </provider>

    </application>

</manifest>

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools">

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

<application

android:allowBackup="true"

android:dataExtractionRules="@xml/data_extraction_rules"

android:fullBackupContent="@xml/backup_rules"

android:icon="@mipmap/ic_launcher"

android:label="@string/app_name"

android:supportsRtl="true"

android:theme="@style/Theme.Mp4toMp3Project"

tools:targetApi="31">

<activity

android:name=".MainActivity"

android:exported="true">

<intent-filter>

</intent-filter>

</activity>

<provider

android:name="androidx.core.content.FileProvider"

android:authorities="${applicationId}.provider"

android:grantUriPermissions="true"

android:exported="false">

<meta-data

android:name="android.support.FILE_PROVIDER_PATHS"

android:resource="@xml/provider_paths" />

</provider>

</application>

</manifest>

Here you need to replace your own package name and structure and now we need to create this file_paths.xml file inside the xml directory which holds the path where we will be saving the mp3files

xml/file_paths.xml

<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="external_files" path="." />
    <paths xmlns:android="http://schemas.android.com/apk/res/android">
        <external-path name="myapp" path="MyApp/Downloads" />
    </paths>
</paths>

<external-path name="external_files" path="." />

<external-path name="myapp" path="MyApp/Downloads" />

</paths>

Editing the Main Layout

Now we need to edit the activity_main.xml file for the project where we will have one button to select the video from the gallery as shown below.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.mp4tomp3project.MainActivity">
    

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="89dp"
        android:text="Select Video"
        android:backgroundTint="@color/black"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.65" />

</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout

xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

tools:context="com.example.mp4tomp3project.MainActivity">

<Button

android:id="@+id/button"

android:layout_width="match_parent"

android:layout_height="89dp"

android:text="Select Video"

android:backgroundTint="@color/black"

app:layout_constraintBottom_toBottomOf="parent"

app:layout_constraintEnd_toEndOf="parent"

app:layout_constraintHorizontal_bias="0.0"

app:layout_constraintStart_toStartOf="parent"

app:layout_constraintTop_toTopOf="parent"

app:layout_constraintVertical_bias="0.65" />

</androidx.constraintlayout.widget.ConstraintLayout>

And now we need to edit the MainActivity.java file and copy paste the following code

MainActivity.java

package com.example.mp4tomp3project;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.annotation.SuppressLint;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.view.View;
import android.widget.Button;
import android.Manifest;
import android.widget.Toast;

import java.io.File;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    private static final int REQUEST_PICK_VIDEO = 1;

    private static final int REQUEST_PERMISSION_READ_EXTERNAL_STORAGE = 2;


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


        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, REQUEST_PERMISSION_READ_EXTERNAL_STORAGE);
            }
        }

        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                pickVideoFromGallery();
            }
        });
    }

    private void pickVideoFromGallery() {
        Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Video.Media.EXTERNAL_CONTENT_URI);
        intent.setType("video/mp4");
        startActivityForResult(Intent.createChooser(intent, "Select Video"), REQUEST_PICK_VIDEO);
    }

    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == REQUEST_PERMISSION_READ_EXTERNAL_STORAGE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // Permission granted, you can now access files on external storage
            } else {
                // Permission denied, you cannot access files on external storage
            }
        }
    }

    @SuppressLint("WrongConstant")
    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == REQUEST_PICK_VIDEO && resultCode == RESULT_OK && data != null) {
            Uri videoUri = data.getData();

            try {
                File dir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "MyApp");
                if (!dir.exists()) {
                    dir.mkdirs();
                }
                String fileName = "audio_" + System.currentTimeMillis() + ".mp3";
                File outputFile = new File(dir, fileName);
                new AudioExtractor().genVideoUsingMuxer(videoUri.getPath(), outputFile.getPath(), -1, -1, true, false);
                Toast.makeText(this,"Mp3 Audio Created Successfully",Toast.LENGTH_LONG).show();

            } catch (IOException e) {
                throw new RuntimeException(e);
            }

        }
    }
}

package com.example.mp4tomp3project;

import androidx.annotation.NonNull;

import androidx.annotation.Nullable;

import androidx.appcompat.app.AppCompatActivity;

import android.annotation.SuppressLint;

import android.content.Intent;

import android.content.pm.PackageManager;

import android.net.Uri;

import android.os.Build;

import android.os.Bundle;

import android.os.Environment;

import android.provider.MediaStore;

import android.view.View;

import android.widget.Button;

import android.Manifest;

import android.widget.Toast;

import java.io.File;

import java.io.IOException;

public class MainActivity extends AppCompatActivity {

private static final int REQUEST_PICK_VIDEO = 1;

private static final int REQUEST_PERMISSION_READ_EXTERNAL_STORAGE = 2;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {

if (checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {

requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, REQUEST_PERMISSION_READ_EXTERNAL_STORAGE);

}

Button button = findViewById(R.id.button);

button.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

pickVideoFromGallery();

}

});

}

private void pickVideoFromGallery() {

Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Video.Media.EXTERNAL_CONTENT_URI);

intent.setType("video/mp4");

startActivityForResult(Intent.createChooser(intent, "Select Video"), REQUEST_PICK_VIDEO);

}

public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {

super.onRequestPermissionsResult(requestCode, permissions, grantResults);

if (requestCode == REQUEST_PERMISSION_READ_EXTERNAL_STORAGE) {

if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

// Permission granted, you can now access files on external storage

} else {

// Permission denied, you cannot access files on external storage

}

@SuppressLint("WrongConstant")

@Override

protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {

super.onActivityResult(requestCode, resultCode, data);

if (requestCode == REQUEST_PICK_VIDEO && resultCode == RESULT_OK && data != null) {

Uri videoUri = data.getData();

try {

File dir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "MyApp");

if (!dir.exists()) {

dir.mkdirs();

}

String fileName = "audio_" + System.currentTimeMillis() + ".mp3";

File outputFile = new File(dir, fileName);

new AudioExtractor().genVideoUsingMuxer(videoUri.getPath(), outputFile.getPath(), -1, -1, true, false);

Toast.makeText(this,"Mp3 Audio Created Successfully",Toast.LENGTH_LONG).show();

} catch (IOException e) {

throw new RuntimeException(e);

}

As you can see inside the java code we are using the AudioExtractor class to basically convert the video files that we select from the gallery to convert to mp3 audio files. And we are taking the permissions at runtime from the user for android devices which are above 10. And after that we are saving the mp3 audio files inside the external storage in the downloads folder. And then we are showing the toast message to the user that your mp3 file is generated successfully.

And now we need to create the AudioExtractor.java class where we need to copy paste the below java code as shown below

AudioExtractor.java

package com.example.mp4tomp3project;

import android.annotation.SuppressLint;
import android.media.MediaCodec;
import android.media.MediaExtractor;
import android.media.MediaFormat;
import android.media.MediaMetadataRetriever;
import android.media.MediaMuxer;
import android.util.Log;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.HashMap;

// Copyright (c) 2018 ArsalImam
// All Rights Reserved
//
public class AudioExtractor {

    private static final int DEFAULT_BUFFER_SIZE = 1 * 1024 * 1024;
    private static final String TAG = "AudioExtractorDecoder";

    /**
     * @param srcPath  the path of source video file.
     * @param dstPath  the path of destination video file.
     * @param startMs  starting time in milliseconds for trimming. Set to
     *                 negative if starting from beginning.
     * @param endMs    end time for trimming in milliseconds. Set to negative if
     *                 no trimming at the end.
     * @param useAudio true if keep the audio track from the source.
     * @param useVideo true if keep the video track from the source.
     * @throws IOException
     */
    @SuppressLint("NewApi")
    public void genVideoUsingMuxer(String srcPath, String dstPath, int startMs, int endMs, boolean useAudio, boolean useVideo) throws IOException {
        // Set up MediaExtractor to read from the source.
        MediaExtractor extractor = new MediaExtractor();
        extractor.setDataSource(srcPath);
        int trackCount = extractor.getTrackCount();
        // Set up MediaMuxer for the destination.
        MediaMuxer muxer;
        muxer = new MediaMuxer(dstPath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
        // Set up the tracks and retrieve the max buffer size for selected
        // tracks.
        HashMap<Integer, Integer> indexMap = new HashMap<Integer, Integer>(trackCount);
        int bufferSize = -1;
        for (int i = 0; i < trackCount; i++) {
            MediaFormat format = extractor.getTrackFormat(i);
            String mime = format.getString(MediaFormat.KEY_MIME);
            boolean selectCurrentTrack = false;
            if (mime.startsWith("audio/") && useAudio) {
                selectCurrentTrack = true;
            } else if (mime.startsWith("video/") && useVideo) {
                selectCurrentTrack = true;
            }
            if (selectCurrentTrack) {
                extractor.selectTrack(i);
                int dstIndex = muxer.addTrack(format);
                indexMap.put(i, dstIndex);
                if (format.containsKey(MediaFormat.KEY_MAX_INPUT_SIZE)) {
                    int newSize = format.getInteger(MediaFormat.KEY_MAX_INPUT_SIZE);
                    bufferSize = newSize > bufferSize ? newSize : bufferSize;
                }
            }
        }
        if (bufferSize < 0) {
            bufferSize = DEFAULT_BUFFER_SIZE;
        }
        // Set up the orientation and starting time for extractor.
        MediaMetadataRetriever retrieverSrc = new MediaMetadataRetriever();
        retrieverSrc.setDataSource(srcPath);
        String degreesString = retrieverSrc.extractMetadata(MediaMetadataRetriever.METADATA_KEY_VIDEO_ROTATION);
        if (degreesString != null) {
            int degrees = Integer.parseInt(degreesString);
            if (degrees >= 0) {
                muxer.setOrientationHint(degrees);
            }
        }
        if (startMs > 0) {
            extractor.seekTo(startMs * 1000, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
        }
        // Copy the samples from MediaExtractor to MediaMuxer. We will loop
        // for copying each sample and stop when we get to the end of the source
        // file or exceed the end time of the trimming.
        int offset = 0;
        int trackIndex = -1;
        ByteBuffer dstBuf = ByteBuffer.allocate(bufferSize);
        MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
        muxer.start();
        while (true) {
            bufferInfo.offset = offset;
            bufferInfo.size = extractor.readSampleData(dstBuf, offset);
            if (bufferInfo.size < 0) {
                Log.d(TAG, "Saw input EOS.");
                bufferInfo.size = 0;
                break;
            } else {
                bufferInfo.presentationTimeUs = extractor.getSampleTime();
                if (endMs > 0 && bufferInfo.presentationTimeUs > (endMs * 1000)) {
                    Log.d(TAG, "The current sample is over the trim end time.");
                    break;
                } else {
                    bufferInfo.flags = extractor.getSampleFlags();
                    trackIndex = extractor.getSampleTrackIndex();
                    muxer.writeSampleData(indexMap.get(trackIndex), dstBuf, bufferInfo);
                    extractor.advance();
                }
            }
        }
        muxer.stop();
        muxer.release();
        return;
    }
}

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package com.example.mp4tomp3project;

import android.annotation.SuppressLint;

import android.media.MediaCodec;

import android.media.MediaExtractor;

import android.media.MediaFormat;

import android.media.MediaMetadataRetriever;

import android.media.MediaMuxer;

import android.util.Log;

import java.io.IOException;

import java.nio.ByteBuffer;

import java.util.HashMap;

public class AudioExtractor {

private static final int DEFAULT_BUFFER_SIZE = 1 * 1024 * 1024;

private static final String TAG = "AudioExtractorDecoder";

/**

* @param srcPath the path of source video file.

* @param dstPath the path of destination video file.

* @param startMs starting time in milliseconds for trimming. Set to

* negative if starting from beginning.

* @param endMs end time for trimming in milliseconds. Set to negative if

* no trimming at the end.

* @param useAudio true if keep the audio track from the source.

* @param useVideo true if keep the video track from the source.

* @throws IOException

@SuppressLint("NewApi")

public void genVideoUsingMuxer(String srcPath, String dstPath, int startMs, int endMs, boolean useAudio, boolean useVideo) throws IOException {

// Set up MediaExtractor to read from the source.

MediaExtractor extractor = new MediaExtractor();

extractor.setDataSource(srcPath);

int trackCount = extractor.getTrackCount();

// Set up MediaMuxer for the destination.

MediaMuxer muxer;

muxer = new MediaMuxer(dstPath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);

// Set up the tracks and retrieve the max buffer size for selected

// tracks.

HashMap<Integer, Integer> indexMap = new HashMap<Integer, Integer>(trackCount);

int bufferSize = -1;

for (int i = 0; i < trackCount; i++) {

MediaFormat format = extractor.getTrackFormat(i);

String mime = format.getString(MediaFormat.KEY_MIME);

boolean selectCurrentTrack = false;

if (mime.startsWith("audio/") && useAudio) {

selectCurrentTrack = true;

} else if (mime.startsWith("video/") && useVideo) {

selectCurrentTrack = true;

}

if (selectCurrentTrack) {

extractor.selectTrack(i);

int dstIndex = muxer.addTrack(format);

indexMap.put(i, dstIndex);

if (format.containsKey(MediaFormat.KEY_MAX_INPUT_SIZE)) {

int newSize = format.getInteger(MediaFormat.KEY_MAX_INPUT_SIZE);

bufferSize = newSize > bufferSize ? newSize : bufferSize;

}

if (bufferSize < 0) {

bufferSize = DEFAULT_BUFFER_SIZE;

}

// Set up the orientation and starting time for extractor.

MediaMetadataRetriever retrieverSrc = new MediaMetadataRetriever();

retrieverSrc.setDataSource(srcPath);

String degreesString = retrieverSrc.extractMetadata(MediaMetadataRetriever.METADATA_KEY_VIDEO_ROTATION);

if (degreesString != null) {

int degrees = Integer.parseInt(degreesString);

if (degrees >= 0) {

muxer.setOrientationHint(degrees);

}

if (startMs > 0) {

extractor.seekTo(startMs * 1000, MediaExtractor.SEEK_TO_CLOSEST_SYNC);

}

// Copy the samples from MediaExtractor to MediaMuxer. We will loop

// for copying each sample and stop when we get to the end of the source

// file or exceed the end time of the trimming.

int offset = 0;

int trackIndex = -1;

ByteBuffer dstBuf = ByteBuffer.allocate(bufferSize);

MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();

muxer.start();

while (true) {

bufferInfo.offset = offset;

bufferInfo.size = extractor.readSampleData(dstBuf, offset);

if (bufferInfo.size < 0) {

Log.d(TAG, "Saw input EOS.");

bufferInfo.size = 0;

break;

} else {

bufferInfo.presentationTimeUs = extractor.getSampleTime();

if (endMs > 0 && bufferInfo.presentationTimeUs > (endMs * 1000)) {

Log.d(TAG, "The current sample is over the trim end time.");

break;

} else {

bufferInfo.flags = extractor.getSampleFlags();

trackIndex = extractor.getSampleTrackIndex();

muxer.writeSampleData(indexMap.get(trackIndex), dstBuf, bufferInfo);

extractor.advance();

}

muxer.stop();

muxer.release();

return;

}

As you can see inside this java code of the library we are using the MediaMuxer class in the background to convert the input video file to audio file.