Streaming AAC audio with Android

Question

As I understand it, Android will only play AAC format audio if it's encoded as MPEG-4 or 3GPP.

I'm able to play AAC audio encoded as M4A when it's local to the app, but it fails when obtaining it from a server.

The following works, as the m4a file is held locally in the res/raw directory.

MediaPlayer mp = MediaPlayer.create(this, R.raw.*file*);
mp.start();

The following doesn't work. (But does with MP3's).

Uri uri = Uri.parse("http://*example.com*/blah.m4a");
MediaPlayer mp = MediaPlayer.create(this, uri);
mp.start();

Can anyone shed any light on why it fails when the m4a audio file is not local?

Here's (some of) the error...

ERROR/PlayerDriver(542): Command PLAYER_INIT completed with an error or info UNKNOWN PVMFStatus
ERROR/MediaPlayer(769): error (200, -32)  
WARN/PlayerDriver(542): PVMFInfoErrorHandlingComplete  
DEBUG/MediaPlayer(769): create failed:  
DEBUG/MediaPlayer(769): java.io.IOException: Prepare failed.: status=0xC8  
DEBUG/MediaPlayer(769):     at android.media.MediaPlayer.prepare(Native Method)  
DEBUG/MediaPlayer(769):     at android.media.MediaPlayer.create(MediaPlayer.java:530)  
DEBUG/MediaPlayer(769):     at android.media.MediaPlayer.create(MediaPlayer.java:507)   
...

I'm targeting SDK 1.6.

Couchant

You're confusing encoding with file formats. AAC is an audio encoding format. M4A is a file type, or package, that sits around the AAC data. 3GPP is similar but can contain other types of encoded audio. See here developer.android.com/guide/appendix/media-formats.html and here en.wikipedia.org/wiki/M4a. – Stavros

True, I should have described 3GPP and M4A as "containers" for AAC audio. Off the top of my head I think M4A may only be used for static files, and 3GPP can only stream using RTSP rather than HTTP? This would cause problems for HTTP streaming. Correct me if I'm wrong... – Couchant

Answer 1

This work-around allows you to play M4A files from the net (and AAC files in other containers such as MP4 & 3GP). It simply downloads the file and plays from the cache.

private File mediaFile;

private void playAudio(String mediaUrl) {
    try {
        URLConnection cn = new URL(mediaUrl).openConnection();
        InputStream is = cn.getInputStream();

        // create file to store audio
        mediaFile = new File(this.getCacheDir(),"mediafile");
        FileOutputStream fos = new FileOutputStream(mediaFile);   
        byte buf[] = new byte[16 * 1024];
        Log.i("FileOutputStream", "Download");

        // write to file until complete
        do {
            int numread = is.read(buf);   
            if (numread <= 0)  
                break;
            fos.write(buf, 0, numread);
        } while (true);
        fos.flush();
        fos.close();
        Log.i("FileOutputStream", "Saved");
        MediaPlayer mp = new MediaPlayer();

        // create listener to tidy up after playback complete
        MediaPlayer.OnCompletionListener listener = new MediaPlayer.OnCompletionListener() {
            public void onCompletion(MediaPlayer mp) {
                // free up media player
                mp.release();
                Log.i("MediaPlayer.OnCompletionListener", "MediaPlayer Released");
            }
        };
        mp.setOnCompletionListener(listener);

        FileInputStream fis = new FileInputStream(mediaFile);
        // set mediaplayer data source to file descriptor of input stream
        mp.setDataSource(fis.getFD());
        mp.prepare();
        Log.i("MediaPlayer", "Start Player");
        mp.start();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

Couchant

Good idea but of course this requires the entire file to be downloaded first before it can be played. Could be useful for some situations but obviously not suitable as a streaming solution. – Stavros

That's true, though this code can be built on to create a streaming solution using a local file or files as a makeshift circular buffer. It's unfortunate that the MediaPlayer cannot receive from an InputStream or you'd be able to do a circular buffer in the standard way. – Couchant

Answer 2

I tried it too but I could not find out the solution!

At the last Google I/O I saw something that helped me a lot. It is Extending from MediaPlayer and improve a lot of things! Take a look.

EXOPLAYER CAN HELP YOU A LOT

Check this part of the example:

private static final int BUFFER_SEGMENT_SIZE = 64 * 1024;
private static final int BUFFER_SEGMENT_COUNT = 256;
...

// String with the url of the radio you want to play
String url = getRadioUrl();
Uri radioUri = Uri.parse(url);
// Settings for exoPlayer
Allocator allocator = new DefaultAllocator(BUFFER_SEGMENT_SIZE);
String userAgent = Util.getUserAgent(context, "ExoPlayerDemo");
DataSource dataSource = new DefaultUriDataSource(context, null, userAgent);
ExtractorSampleSource sampleSource = new ExtractorSampleSource(
radioUri, dataSource, allocator, BUFFER_SEGMENT_SIZE * BUFFER_SEGMENT_COUNT);
audioRenderer = new MediaCodecAudioTrackRenderer(sampleSource);
// Prepare ExoPlayer
exoPlayer.prepare(audioRenderer);

EXOPLAYER- I can play anything from streamings (video and audio)!

LET ME KNOW IF YOU NEED HELP TO IMPLEMENT IT! :)

Turnsole

Answer 3

This is a wild shot in the dark, but I have seen similar behavior with the flash player where it actually ignores the file name and only relies on the MIME type sent by the server. Any idea what headers are being sent down from example.com? You might want to try wrapping your blah.m4a in a page that can set the headers and then stream the binary data. Give these types a shot and the community would appreciate a confirmation of what works:

audio/mpeg audio/mp4a audio/mp4a-latm audio/aac audio/x-aac

Irrationality

A good suggestion - thanks. Unfortunately I've had no luck trying an array of possible content-types. For reference, I've listed the ones that have not worked below. It's still possible it's something to do with HTTP headers - or something - it might be that it's very fussy about what it can be fed. audio/m4a audio/aac audio/aacp audio/x-aac audio/mpeg audio/mp4a audio/mp4a-latm audio/mp4 – Couchant

I definitely experienced an issue with this. For our streaming purposes, the MediaPlayer would not play the streaming file unless the Http header content-type was set correctly. Interestingly, the content length was not required though. – Stavros

Answer 4

I found that if you record the audio file on Android with the following properties, you are then able to play it on your server. It also plays well in the HTML Audio Element, however only on Firefox at the moment. This may change in the future.

Android (JAVA):

mediaRecorder = new MediaRecorder();
mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.HE_AAC);
mediaRecorder.setAudioSamplingRate(44100);
mediaRecorder.setAudioChannels(1);
mediaRecorder.setOutputFile(filePath);

HTML:

<audio id="audioMediaControl" controls src="yourfile.m4a"> Your browser does not support the audio element. </audio>

Rennes

Answer 5

try --

1) MP.prepareAsync()

2) onPrepared() { mp.start() }

Canty