How to merge audio and video using MediaMuxer?
<p>I'm developing an Android App with mp3 audio file and mp4 video file with(no sound).</p>

<p>Now I want to mix them and create a new mp4 video file(with sound). From Android 4.3, Google suggests using the MediaMuxer class to mix stream audio and video. I have tried many times without success.</p>

<p>Here is the code:</p>

<pre><code>    private void muxing() {

    String outputFile = "";

    try {

        File file = new File(Environment.getExternalStorageDirectory() + "/final2.mp4");
        file.createNewFile();
        outputFile = file.getAbsolutePath();
        MediaExtractor videoExtractor = new MediaExtractor();
        videoExtractor.setDataSource(Environment.getExternalStorageDirectory().toString()+"/vd1.h264");
        MediaExtractor audioExtractor = new MediaExtractor();
        audioExtractor.setDataSource(Environment.getExternalStorageDirectory()+"/audioVideoDir/audio.m4a");
        MediaMuxer muxer = new MediaMuxer(outputFile, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);

        videoExtractor.selectTrack(0);
        MediaFormat videoFormat = videoExtractor.getTrackFormat(0);
        int videoTrack = muxer.addTrack(videoFormat);

        audioExtractor.selectTrack(0);
        MediaFormat audioFormat = audioExtractor.getTrackFormat(0);
        int audioTrack = muxer.addTrack(audioFormat);
        boolean sawEOS = false;
        int frameCount = 0;
        int offset = 100;
        int sampleSize = 256 * 1024;
        ByteBuffer videoBuf = ByteBuffer.allocate(sampleSize);
        ByteBuffer audioBuf = ByteBuffer.allocate(sampleSize);
        MediaCodec.BufferInfo videoBufferInfo = new MediaCodec.BufferInfo();
        MediaCodec.BufferInfo audioBufferInfo = new MediaCodec.BufferInfo();


        videoExtractor.seekTo(0, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
        audioExtractor.seekTo(0, MediaExtractor.SEEK_TO_CLOSEST_SYNC);

        muxer.start();

        while (!sawEOS)
        {
            videoBufferInfo.offset = offset;
            videoBufferInfo.size = videoExtractor.readSampleData(videoBuf, offset);


            if (videoBufferInfo.size &lt; 0 || audioBufferInfo.size &lt; 0)
            {
               // Log.d(TAG, "saw input EOS.");
                sawEOS = true;
                videoBufferInfo.size = 0;

            }
            else
            {
                videoBufferInfo.presentationTimeUs = videoExtractor.getSampleTime();
                videoBufferInfo.flags = videoExtractor.getSampleFlags();
                muxer.writeSampleData(videoTrack, videoBuf, videoBufferInfo);
                videoExtractor.advance();


                frameCount++;

            }
        }

        Toast.makeText(getApplicationContext() , "frame:" + frameCount , Toast.LENGTH_SHORT).show();



        boolean sawEOS2 = false;
        int frameCount2 =0;
        while (!sawEOS2)
        {
            frameCount2++;

            audioBufferInfo.offset = offset;
            audioBufferInfo.size = audioExtractor.readSampleData(audioBuf, offset);

            if (videoBufferInfo.size &lt; 0 || audioBufferInfo.size &lt; 0)
            {
              //  Log.d(TAG, "saw input EOS.");
                sawEOS2 = true;
                audioBufferInfo.size = 0;
            }
            else
            {
                audioBufferInfo.presentationTimeUs = audioExtractor.getSampleTime();
                audioBufferInfo.flags = audioExtractor.getSampleFlags();
                muxer.writeSampleData(audioTrack, audioBuf, audioBufferInfo);
                audioExtractor.advance();

            }
        }

        Toast.makeText(getApplicationContext() , "frame:" + frameCount2 , Toast.LENGTH_SHORT).show();

        muxer.stop();
        muxer.release();


    } catch (IOException e) {

    } catch (Exception e) {

    }
}
</code></pre>

<p>I get the below error:</p>

<p><strong>Unknown mime type 'audio/mpeg'. 12-09 11:58:33.569: A/MPEG4Writer(332): frameworks/av/media/libstagefright/MPEG4Writer.cpp:2699 CHECK(!"should not be here, unknown mime type.")</strong> </p>

<p>Any solution to resolve my issue with MediaMuxer API from Google? Even i tried with ffmpeg after merging of audio and video together video doesn't plays in default video player of android device but it loads in Vlc player.</p>

<p><strong>FFMPEG</strong> followed from here:<a href="https://github.com/WritingMinds/ffmpeg-android-java" rel="noreferrer">https://github.com/WritingMinds/ffmpeg-android-java</a></p>