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android – MediaPlayer stutters at start of mp3 playback

Posted by: admin April 23, 2020 Leave a comment

Questions:

I’ve been having a problem playing an mp3 file stored in a raw resource: when the file first starts playing, it generates perhaps a quarter of a second of sound and then restarts. (I know that this is basically a duplicate of the problem described here, but the solution offered there hasn’t worked for me.) I have tried several things and have made some progress on the problem, but it isn’t totally fixed.

Here’s how I’m setting up to play a file:

mPlayer.reset();
try {
    AssetFileDescriptor afd = getResources().openRawResourceFd(mAudioId);
    if (afd == null) {
        Toast.makeText(mOwner, "Could not load sound.",
                Toast.LENGTH_LONG).show();
        return;
    }
    mPlayer.setDataSource(afd.getFileDescriptor(),
            afd.getStartOffset(), afd.getLength());
    afd.close();
    mPlayer.prepare();
} catch (Exception e) {
    Log.d(LOG_TAG, "Could not load sound.", e);
    Toast.makeText(mOwner, "Could not load sound.", Toast.LENGTH_LONG)
            .show();
}

If I exit the activity (which calls mPlayer.release()) and come back to it (creating a new MediaPlayer), the stutter is usually (but not always) gone—provided I load the same sound file. I tried a couple of things that made no difference:

  • Load the sound file as an asset instead of as a resource.
  • Create the MediaPlayer using MediaPlayer.create(getContext(), mAudioId) and skip the calls to setDataSource(...) and prepare().

Then I noticed that LogCat always shows this line at about the time that playback starts:

DEBUG/AudioSink(37): bufferCount (4) is too small and increased to 12

It got me wondering if the stuttering is due to the apparent rebuffering. This led me to try something else:

  • After calling prepare(), call mPlayer.start() and immediately call mPlayer.pause().

To my pleasant surprise, this had a big effect. A great deal of the stutter is gone, plus no sound (that I can hear) is actually played at that point in the process.

However, it still stutters from time to time when I call mPlayer.start() for real. Plus, this seems like a huge kludge. Is there any way to kill this problem completely and cleanly?

EDIT More info; not sure if related. If I call pause() during playback, seek to an earlier position, and call start() again, I hear a short bit (~1/4 sec) of additional sound from where it was paused before it starts playing at the new position. This seems to point to more buffering problems.

Also, the stuttering (and paused buffer) problems show up on emulators from 1.6 through 3.0.

How to&Answers:

AFAIK the buffers that MediaPlayer creates internally are for storing decompressed samples, not for storing prefetched compressed data. I suspect your stuttering comes from I/O slowness as it loads more MP3 data for decompression.

I recently had to solve a similar problem with video playback. Thanks to MediaPlayer being unable to play an arbitrary InputStream (the API is strangely lame) the solution I came up with was to write a small in-process webserver for serving up local files (on the SD card) over HTTP. MediaPlayer then loads it via a URI of the form http://127.0.0.1:8888/videofilename.

EDIT:

Below is the StreamProxy class I use to feed content into a MediaPlayer instance. The basic use is that you instantiate it, start() it, and set your media player going with something like MediaPlayer.setDataSource("http://127.0.0.1:8888/localfilepath");

I should note that it is rather experimental and probably not entirely bug-free. It was written to solve a similar problem to yours, namely that MediaPlayer cannot play a file that is also being downloaded. Streaming a file locally in this way works around that restriction (i.e. I have a thread downloading the file while the StreamProxy feeds it into mediaplayer).

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import java.net.UnknownHostException;
import android.os.AsyncTask;
import android.os.Looper;
import android.util.Log;

public class StreamProxy implements Runnable {

    private static final int SERVER_PORT=8888;

    private Thread thread;
    private boolean isRunning;
    private ServerSocket socket;
    private int port;

    public StreamProxy() {

        // Create listening socket
        try {
          socket = new ServerSocket(SERVER_PORT, 0, InetAddress.getByAddress(new byte[] {127,0,0,1}));
          socket.setSoTimeout(5000);
          port = socket.getLocalPort();
        } catch (UnknownHostException e) { // impossible
        } catch (IOException e) {
          Log.e(TAG, "IOException initializing server", e);
        }

    }

    public void start() {
        thread = new Thread(this);
        thread.start();
    }

    public void stop() {
        isRunning = false;
        thread.interrupt();
        try {
            thread.join(5000);
        } catch (InterruptedException e) {
          e.printStackTrace();
        }
    }

    @Override
      public void run() {
        Looper.prepare();
        isRunning = true;
        while (isRunning) {
          try {
            Socket client = socket.accept();
            if (client == null) {
              continue;
            }
            Log.d(TAG, "client connected");

            StreamToMediaPlayerTask task = new StreamToMediaPlayerTask(client);
            if (task.processRequest()) {
                task.execute();
            }

          } catch (SocketTimeoutException e) {
            // Do nothing
          } catch (IOException e) {
            Log.e(TAG, "Error connecting to client", e);
          }
        }
        Log.d(TAG, "Proxy interrupted. Shutting down.");
      }




    private class StreamToMediaPlayerTask extends AsyncTask<String, Void, Integer> {

        String localPath;
        Socket client;
        int cbSkip;

        public StreamToMediaPlayerTask(Socket client) {
            this.client = client;
        }

        public boolean processRequest() {
            // Read HTTP headers
            String headers = "";
            try {
              headers = Utils.readTextStreamAvailable(client.getInputStream());
            } catch (IOException e) {
              Log.e(TAG, "Error reading HTTP request header from stream:", e);
              return false;
            }

            // Get the important bits from the headers
            String[] headerLines = headers.split("\n");
            String urlLine = headerLines[0];
            if (!urlLine.startsWith("GET ")) {
                Log.e(TAG, "Only GET is supported");
                return false;               
            }
            urlLine = urlLine.substring(4);
            int charPos = urlLine.indexOf(' ');
            if (charPos != -1) {
                urlLine = urlLine.substring(1, charPos);
            }
            localPath = urlLine;

            // See if there's a "Range:" header
            for (int i=0 ; i<headerLines.length ; i++) {
                String headerLine = headerLines[i];
                if (headerLine.startsWith("Range: bytes=")) {
                    headerLine = headerLine.substring(13);
                    charPos = headerLine.indexOf('-');
                    if (charPos>0) {
                        headerLine = headerLine.substring(0,charPos);
                    }
                    cbSkip = Integer.parseInt(headerLine);
                }
            }
            return true;
        }

        @Override
        protected Integer doInBackground(String... params) {

                        long fileSize = GET CONTENT LENGTH HERE;

            // Create HTTP header
            String headers = "HTTP/1.0 200 OK\r\n";
            headers += "Content-Type: " + MIME TYPE HERE + "\r\n";
            headers += "Content-Length: " + fileSize  + "\r\n";
            headers += "Connection: close\r\n";
            headers += "\r\n";

            // Begin with HTTP header
            int fc = 0;
            long cbToSend = fileSize - cbSkip;
            OutputStream output = null;
            byte[] buff = new byte[64 * 1024];
            try {
                output = new BufferedOutputStream(client.getOutputStream(), 32*1024);                           
                output.write(headers.getBytes());

                // Loop as long as there's stuff to send
                while (isRunning && cbToSend>0 && !client.isClosed()) {

                    // See if there's more to send
                    File file = new File(localPath);
                    fc++;
                    int cbSentThisBatch = 0;
                    if (file.exists()) {
                        FileInputStream input = new FileInputStream(file);
                        input.skip(cbSkip);
                        int cbToSendThisBatch = input.available();
                        while (cbToSendThisBatch > 0) {
                            int cbToRead = Math.min(cbToSendThisBatch, buff.length);
                            int cbRead = input.read(buff, 0, cbToRead);
                            if (cbRead == -1) {
                                break;
                            }
                            cbToSendThisBatch -= cbRead;
                            cbToSend -= cbRead;
                            output.write(buff, 0, cbRead);
                            output.flush();
                            cbSkip += cbRead;
                            cbSentThisBatch += cbRead;
                        }
                        input.close();
                    }

                    // If we did nothing this batch, block for a second
                    if (cbSentThisBatch == 0) {
                        Log.d(TAG, "Blocking until more data appears");
                        Thread.sleep(1000);
                    }
                }
            }
            catch (SocketException socketException) {
                Log.e(TAG, "SocketException() thrown, proxy client has probably closed. This can exit harmlessly");
            }
            catch (Exception e) {
                Log.e(TAG, "Exception thrown from streaming task:");
                Log.e(TAG, e.getClass().getName() + " : " + e.getLocalizedMessage());
                e.printStackTrace();                
            }

            // Cleanup
            try {
                if (output != null) {
                    output.close();
                }
                client.close();
            }
            catch (IOException e) {
                Log.e(TAG, "IOException while cleaning up streaming task:");                
                Log.e(TAG, e.getClass().getName() + " : " + e.getLocalizedMessage());
                e.printStackTrace();                
            }

            return 1;
        }

    }
}

Answer:

Would using prepareAsync and responding to setOnPreparedListener suit you better? Depending on your activity workflow, when the MediaPlayer is first initialized you could set the preparation listener and then call mPlayer.prepareAsync() later once you’re actually loading the resource, then start playback there. I use something similar, albeit for a network-based streaming resource:

MediaPlayer m_player;
private ProgressDialog m_progressDialog = null;

...

try {
    if (m_player != null) {
    m_player.reset();
    } else {
    m_player = new MediaPlayer();
    }

    m_progressDialog = ProgressDialog
        .show(this,
            getString(R.string.progress_dialog_please_wait),
            getString(R.string.progress_dialog_buffering),
            true);

    m_player.setOnPreparedListener(this);
    m_player.setAudioStreamType(AudioManager.STREAM_MUSIC);
    m_player.setDataSource(someSource);
    m_player.prepareAsync();
} catch (Exception ex) {
}

...

public void onPrepared(MediaPlayer mp) {
    if (m_progressDialog != null && m_progressDialog.isShowing()) {
      m_progressDialog.dismiss();
    }

    m_player.start();
}

There’s obviously more to a complete solution (error-handling, etc.) but I think this should work as a good example to start from that you can pull the streaming out of.