MediaPlayer在mp3播放开始时口吃

Question

我在播放存储在原始资源中的mp3文件时遇到了问题:当文件首次开始播放时,它可能会生成四分之一秒的声音,然后重新启动.(我知道这基本上是这里描述的问题的重复,但是那里提供的解决方案对我来说没有用.)我已经尝试了几个方面并且在这个问题上取得了一些进展,但它并没有完全修复.

这是我设置播放文件的方式:

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();
}

如果我退出活动(调用mPlayer.release())并返回它(创建一个新的MediaPlayer),口吃通常(但不总是)消失 - 只要我加载相同的声音文件.我尝试了几件没有任何区别的事情:

• 将声音文件作为资源而不是资源加载.
• 使用创建的MediaPlayer MediaPlayer.create(getContext(), mAudioId),并跳到调用setDataSource(...)和prepare().

然后我注意到LogCat总是在播放开始时显示这一行:

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

它让我想知道口吃是否是由于明显的重新缓解.这导致我尝试别的东西:

• 通话后prepare(),拨打电话mPlayer.start()并立即拨打电话mPlayer.pause().

令我惊喜的是,这产生了很大的影响.很多口吃都消失了,加上没有声音(我能听到的)实际上是在这个过程中播放的.

然而,当我呼唤mPlayer.start()真实时,它仍然不时地口吃.此外,这似乎是一个巨大的kludge.有没有办法完全干净地解决这个问题？

编辑更多信息; 不确定是否相关.如果我pause()在播放过程中拨打电话,寻找较早的位置,然后start()再次拨打电话,我会听到一声短暂的声音(约1/4秒)从暂停播放到新位置之前暂停.这似乎指向更多的缓冲问题.

此外,口吃(和暂停的缓冲区)问题出现在1.6到3.0的仿真器上.

Answer 1

AFAIK MediaPlayer内部创建的缓冲区用于存储解压缩的样本,而不是用于存储预取的压缩数据.我怀疑你的口吃来自I/O缓慢,因为它加载了更多的MP3数据进行解压缩.

我最近不得不解决视频播放的类似问题.由于MediaPlayer无法发挥任意性InputStream(API非常蹩脚),我提出的解决方案是编写一个小型进程内Web服务器,通过HTTP提供本地文件(在SD卡上).MediaPlayer然后通过形式为http://127.0.0.1:8888/videofilename的URI加载它.

编辑:

下面是我用来将内容提供给MediaPlayer实例的StreamProxy类.基本用法是你实例化它,start()它,并设置你的媒体播放器MediaPlayer.setDataSource("http://127.0.0.1:8888/localfilepath");

我应该注意到它是相当实验性的,可能并非完全没有bug.它是为解决类似问题而编写的,即MediaPlayer无法播放也正在下载的文件.以这种方式在本地流式传输文件可以解决这个限制(即我有一个线程下载文件,而StreamProxy将它传送到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;
        }

    }
}