音频缓冲区的设置

设置音频数据捕获(capture)和提交(render)缓冲区的数值

问题:

    给音频信息的捕获和提交设置缓冲区数值.小一些的缓冲区会减少时钟周期,但是也会增加传输的次数.这些书只需要在不同的系统上测试.

解决方案:

   音频缓冲区控制(AudioBufferControl)包含于数据源(DataSource)和播放器(Player)中.捕获音频缓冲区数值(Capture Buffer Size)由数据

源控制,提交缓冲区数值(render buffer size)由播放器控制.

    requirements
    related classes
    how to run this sample
    source code

    requirements

    平台                 JDK 1.1.6 或更高版本
    JMF API:             2.0 或更高版本
    Implementation       AJ(All Java),WPP(Windows Performance Pack),SPP(Solaris Performance Pack)

     相关的类

     javax.media.Player
     javax.media.control.BufferControl

     如何执行这个例子

     java AudioBufferControl [-c <capture buf size in millisecs>] [-r <render buf size in millisecs>] <URL>

     例如: java AudioBufferControl -c 62 -r 400 javasound://44100

     代码

    

import java.awt.*;
import javax.media.*;
import javax.media.control.TrackControl;
import javax.media.control.BufferControl;
import javax.media.format.*;
import javax.media.protocol.*;
import javax.media.protocol.DataSource;

/**
 * Sample program to playback the input URL and set the audio capture
 * and rendering buffer sizes.
 */
public class AudioBufferControl extends Frame implements ControllerListener {

    Processor p;
    Object waitSync = new Object();
    boolean stateTransitionOK = true;

    /**
     * Given a DataSource, create a processor and use that processor
     * as a player to playback the media.
     */
    public boolean open(DataSource ds, int captureBufSize, int renderBufSize) {

 System.err.println("create processor for: " + ds.getContentType());

 // Check to see if there's a buffer control on the data source.
 // It could be that we are using a capture data source.
 Control c = (Control)ds.getControl("javax.media.control.BufferControl");
 if (c != null)
     ((BufferControl)c).setBufferLength(captureBufSize);

 try {
     p = Manager.createProcessor(ds);
 } catch (Exception e) {
     System.err.println("Failed to create a processor from the given DataSource: " + e);
     return false;
 }

 p.addControllerListener(this);

 // Put the Processor into configured state.
 p.configure();
 if (!waitForState(p.Configured)) {
     System.err.println("Failed to configure the processor.");
     return false;
 }

 // So I can use it as a player.
 p.setContentDescriptor(null);

 p.realize();
 if (!waitForState(p.Realized)) {
     System.err.println("Failed to realize the processor.");
     return false;
 }

 // After the processor has been realized, we can now set the
 // renderer's buffer size.  We need to do this before the
 // processor is prefetched.
 // We need to loop the array of controls to make sure that we
 // are setting the size of the correct buffer control since
 // the DataSource's controls are also included in the list.
 Control cs[] = p.getControls();
 Object owner;

 for (int i = 0; i < cs.length; i++) {
     if (cs[i] instanceof Owned && cs[i] instanceof BufferControl) {
  owner = ((Owned)cs[i]).getOwner();
  if (owner instanceof Renderer) {
      ((BufferControl)cs[i]).setBufferLength(renderBufSize);
  }
     }
 }

 // Prefetch the processor.
 p.prefetch();
 if (!waitForState(p.Prefetched)) {
     System.err.println("Failed to prefetch the processor.");
     return false;
 }

 // Display the visual & control component if there's one.

 setLayout(new BorderLayout());

 Component cc;

 Component vc;
 if ((vc = p.getVisualComponent()) != null) {
     add("Center", vc);
 }

 if ((cc = p.getControlPanelComponent()) != null) {
     add("South", cc);
 }

 // Start the processor.
 p.start();

 setVisible(true);

 return true;
    }

    public void addNotify() {
 super.addNotify();
 pack();
    }

    /**
     * Block until the processor has transitioned to the given state.
     * Return false if the transition failed.
     */
    boolean waitForState(int state) {
 synchronized (waitSync) {
     try {
  while (p.getState() < state && stateTransitionOK)
      waitSync.wait();
     } catch (Exception e) {}
 }
 return stateTransitionOK;
    }

    /**
     * Controller Listener.
     */
    public void controllerUpdate(ControllerEvent evt) {

 if (evt instanceof ConfigureCompleteEvent ||
     evt instanceof RealizeCompleteEvent ||
     evt instanceof PrefetchCompleteEvent) {
     synchronized (waitSync) {
  stateTransitionOK = true;
  waitSync.notifyAll();
     }
 } else if (evt instanceof ResourceUnavailableEvent) {
     synchronized (waitSync) {
  stateTransitionOK = false;
  waitSync.notifyAll();
     }
 } else if (evt instanceof EndOfMediaEvent) {
     p.setMediaTime(new Time(0));
     //p.start();
     //p.close();
     //System.exit(0);
 } else if (evt instanceof SizeChangeEvent) {
 }
    }

    // Default buffer size in milli-seconds.
    static final int DEF_CAPTURE_SIZE = 62;
    static final int DEF_RENDER_SIZE = 400;

    /**
     * Main program
     */
    public static void main(String [] args) {

 String mlStr = null;
 int captureBufSize = DEF_CAPTURE_SIZE;
 int renderBufSize = DEF_RENDER_SIZE;

 int i = 0;
 while (i < args.length) {
     if (args[i].equals("-c")) {
  i++;
  if (i >= args.length) {
      prUsage();
      System.exit(0);
  }
  try {
      captureBufSize = Integer.parseInt(args[i]);
  } catch (NumberFormatException e) {
      prUsage();
      System.exit(0);
  }
     } else if (args[i].equals("-r")) {
  i++;
  if (i >= args.length) {
      prUsage();
      System.exit(0);
  }
  try {
      renderBufSize = Integer.parseInt(args[i]);
  } catch (NumberFormatException e) {
      prUsage();
      System.exit(0);
  }
     } else {
  mlStr = args[i];
     }
     i++;
 }

 if (mlStr == null) {
     prUsage();
     System.exit(0);
  }

 MediaLocator ml;

 if ((ml = new MediaLocator(mlStr)) == null) {
     System.err.println("Cannot build media locator from: " + mlStr);
     prUsage();
     System.exit(0);
 }

 DataSource ds = null;

 // Create a DataSource given the media locator.
 try {
     ds = Manager.createDataSource(ml);
 } catch (Exception e) {
     System.err.println("Cannot create DataSource from: " + ml);
     System.exit(0);
 }

 AudioBufferControl abc = new AudioBufferControl();
 if (!abc.open(ds, captureBufSize, renderBufSize))
     System.exit(0);
    }

    static void prUsage() {
 System.err.println("Usage: java AudioBufferControl [-c <capture buf size in millisecs>] [-r <render buf size in

millisecs>] <url>");
    }
}