Question

我正在使用JLayer解码MP3，并将其存储为PCM数据。但是，无论我使用什么MP3文件，我总是会得到一个索引为443的ArrayIndexOutOfBoudnsException。我听说这只发生在某些MP3上，但每次播放时我都会播放所有MP3 这是我的代码：

private short[] getPCM(Header frameHeader, Bitstream bs) {
    short[] pcm = null;
    try {
        Decoder d = new Decoder();
        SampleBuffer buffer = (SampleBuffer) d.decodeFrame(frameHeader, bs);
        pcm = buffer.getBuffer();
    } catch (ArrayIndexOutOfBoundsException | DecoderException e) {
        System.err.println("JLayer, stap it");
    }
    return pcm;
}

使用此代码调用该方法：

while ((frameHeader = bs.readFrame()) != null) {
    short[] pcm = getPCM(frameHeader, bs);

    for(short i : pcm){
        try {
            os.write(i);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }       
}

堆栈追踪：

java.lang.ArrayIndexOutOfBoundsException: 433
at javazoom.jl.decoder.Bitstream.get_bits(Unknown Source)
at javazoom.jl.decoder.LayerIIIDecoder.decode(Unknown Source)
at javazoom.jl.decoder.LayerIIIDecoder.decodeFrame(Unknown Source)
at javazoom.jl.decoder.Decoder.decodeFrame(Unknown Source)
at com.dentonposs.Canvas.getPCM(Canvas.java:70)
at com.dentonposs.Canvas.paintComponent(Canvas.java:48)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JLayeredPane.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paintToOffscreen(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paint(Unknown Source)
at javax.swing.RepaintManager.paint(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at java.awt.GraphicsCallback$PaintCallback.run(Unknown Source)
at sun.awt.SunGraphicsCallback.runOneComponent(Unknown Source)
at sun.awt.SunGraphicsCallback.runComponents(Unknown Source)
at java.awt.Container.paint(Unknown Source)
at java.awt.Window.paint(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.access$700(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

从它的外观来看，你试图让解码器一遍又一遍地解码相同的帧。这不起作用，BitStream具有内部状态（指向下一个要读取的位的指针），在解码帧后变为无效。该异常表示它试图读取缓冲区容量。

每帧只需一次调用decodeFrame（）。

编辑：您的堆栈跟踪未显示您实际读取数据的位置。由于异常在组件绘制方法中，我假设您在另一个线程或其他地方读取了该帧。

另外，查看你的getPCM（）方法：该代码永远不会工作。你不能为每一帧创建一个新的解码器实例 - 这根本不起作用，因为解码器有很多内部状态是必要的并且取决于前一帧。您必须只创建一次解码器并将其重新用于所有帧。

看一下javazoom.jl.player.Player的来源 - 它在play（int）方法中显示了一个正确的播放循环（它只有几行，但你必须遵守那里显示的调用顺序，否则你将破坏解码器和解码器持有的对象的正确状态。

Answer 2

您需要在每次调用Bitstream.closeFrame()之间致电readFrame() - 所以

while ((frameHeader = bs.readFrame()) != null) {
    short[] pcm = getPCM(frameHeader, bs);

    bs.closeFrame();

    .. more ..

JLayer总是抛出ArrayIndexOutOfBounds Exception

2 个答案: