Question

This is a code that will attempt to record an audio sample : but i’ve a not constructed AudioFormat object ( that has been passed to DataLine.Info) because i don’t know the sample rate.

EDIT

I have seen that just randomly placing sample rate of 8000 works . But is it fine ? Can i keep any value of sample rate ?

boolean lineIsStopped = false;
TargetDataLine line = null; 
AudioFormat af; // object not constructed through out
DataLine.Info info = new DataLine.Info(TargetDataLine.class, af); // af not initialized
try {
  line = (TargetDataLine)AudioSystem.getLine(info); 
  line.open( af );      
} catch( LineUnavailableException ex ) {
   // handle the error
  }

// now we are ready for an input
// call start to start accepting data from mic
byte data[] = new byte[ line.getBufferSize() / 5 ];
 line.start(); // this statement starts delivering data into the line buffer
// start retreiving data from the line buffer
 int numBytesRead;
 int offset = 0;
 ByteArrayOutputStream out = new ByteArrayOutputStream();
 while( ! lineIsStopped ) { // when the line is not stopped i.e is active
     numBytesRead = line.read( data , offset , data.length );
     // now save the data
     try {
        out.write(data); // writes data to this output stream !
     } catch( Exception exc) {
         System.out.println(exc);
       }
 }

In this how can i construct audio format object without getting any audio sample ?

Answer 1

After reading your comments, you are recording from the mic. In which case you want to set the audio format according to the quality you want from the mic. If you want telephone quality 8k hz would be fine. If you want tape quality 22khz, and if you want CD quality audio 44.1khz. Of course, if you transmitting that over the network then 8khz is probably going to be good enough.

It’s always a good idea to have this be a setting if your application so the user can control what quality they want.