JLayer 播放时改变音量 (JavaZoom)

Question

I build a JLayer that plays a web music stream, which works fine, except for the volume. I cant get it to change.

I already tried the following, but the volume always remains the same, no errors:

public synchronized void setVolume(float vol) {
    Line.Info source = Port.Info.SPEAKER;

    if (AudioSystem.isLineSupported(source)) {
        try {
            Port outline = (Port) AudioSystem.getLine(source);
            outline.open();

            FloatControl volumeControl = (FloatControl) outline.getControl(FloatControl.Type.VOLUME);
            System.out.println("volume: " + volumeControl.getValue());

            volumeControl.setValue(vol);
            System.out.println("new volume: " + volumeControl.getValue());

        } catch (LineUnavailableException ex) {
            System.err.println("source not supported");
            ex.printStackTrace();
        }
    }
}


/*public synchronized void setVolume(double vol) {
    try {
        Mixer.Info[] infos = AudioSystem.getMixerInfo();
        for (Mixer.Info info : infos) {
            Mixer mixer = AudioSystem.getMixer(info);
            if (mixer.isLineSupported(Port.Info.SPEAKER)) {
                Port port = (Port) mixer.getLine(Port.Info.SPEAKER);
                port.open();
                if (port.isControlSupported(FloatControl.Type.VOLUME)) {
                    FloatControl volume = (FloatControl) port.getControl(FloatControl.Type.VOLUME);
                    volume.setValue((float) (vol / 100));
                }
                port.close();
            }
        }
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}*/

Answer 1

My experience is that the implementation of the various Controls supported by Java is somewhat hit-or-miss. I'm not clear why this should be. Perhaps it has to do with the capabilities supported by the OS or particular machine?

In any event, for volume, the MASTER_GAIN is usually the best bet for volume.

The ending portion of the Java Tutorials section on using Controls discusses manipulating the audio data directly. I recommend this option, but getting at the data when using the JavaZoom code can be problematic, and probably involves tweaking the source code of the library.