Java Sound refresh Lines list after attaching a microphone

Question

I have a simple capture/playback Swing app that has to detect if there is no appropriate microphone attached to the computer and warn the user. After a lot of fiddling aroun

Answer 1

Using the original post as inspiration, I came up with this as a means to detect when a mic is lost or gained. It detects (on my system) when a USB mic is plugged in or unplugged. I'm calling it from a background thread loop. The original method did not work for me as there is a built-in mic on the laptop, so I needed to detect the addition of second mic.

...
//call this once somewhere to turn the caching period down for faster detection
    try
    {
        //try to set the caching period, defaults to something like 55 seconds
        com.sun.media.sound.JDK13Services.setCachingPeriod(5);
    }
    catch( Exception e)
    {
        System.err.println("exception attempting to call com.sun.media.sound.JDK13Services.setCachingPeriod->" + e);
    }
...

private int lastNumMics = -1;
private synchronized void micCheck()
{
    Line.Info[] lineInfoArray = AudioSystem.getSourceLineInfo(Port.Info.MICROPHONE);
    int numMics = lineInfoArray == null ? 0 : lineInfoArray.length;
    if( lastNumMics > -1 )
    {
        if( numMics < lastNumMics )
        {
            //MICROPHONE_LOST
        }
        else if( numMics > lastNumMics )
        {
            //MICROPHONE_GAINED
        }
    }
    lastNumMics = numMics;
}

Answer 2

Posting the code that throws the exception might help.

I'm assuming you are only using the Port.Info to detect the presence of a microphone then getting a Dataline to record:

TargetDataLine dataLine = (TargetDataLine) AudioSystem.getLine(new DataLine.Info(TargetDataLine.class, audioFormat));                       
dataLine.open();
dataLine.start();               
dataLine.read(b, offset, len);

Note that you might still get a similar exception when disconnecting the microphone if the microphone is physically disconnected between the time you check for presence and the time you try to get the Dataline to record but connecting the microhpone should not be a problem.