fixed random values being obtained from PCM obtainer

desktop/src/zero1hd/rhythmbullet/desktop/audio/PCMObtainer.java

@@ -62,7 +62,8 @@ public class PCMObtainer implements Observer, PCMSystem {
 		df.setRoundingMode(RoundingMode.HALF_EVEN);
 	}
 
-	private synchronized void calcPCMData() {
+	private synchronized boolean calcPCMData() {
+		boolean empty = true;
 		short chanVal;
 		for (int sid = 0; sid < PCM.length && sid < playingBuffer.remaining(); sid++) {
 			PCM[sid] = 0;
@@ -72,8 +73,16 @@ public class PCMObtainer implements Observer, PCMSystem {
 				}
 			}
 			PCM[sid] /= Short.MAX_VALUE + 1f;
+			
+			if (PCM[sid] != 0) {
+				empty = false;
+			}
+			
 		}
-
+		return empty;
+	}
+	
+	private void checkValidityOfPlaybackBuffer() {
 		// Begin comparison
 		buffer.rewind();
 		if (intermediateBuffer.compareTo(buffer) != 0) {
@@ -85,7 +94,7 @@ public class PCMObtainer implements Observer, PCMSystem {
 			intermediateBuffer.flip();
 		}
 	}
-
+	
 	private void bufferChanged() {
 		playingBuffer.rewind();
 		playingBuffer.put(intermediateBuffer);
@@ -160,9 +169,11 @@ public class PCMObtainer implements Observer, PCMSystem {
 					timeOfLastRead = TimeUtils.millis();
 					
 					//calculate current pcm data and notify that there is new data
-					calcPCMData();
+					checkValidityOfPlaybackBuffer();
-					fft.realForward(PCM);
+					updated = !calcPCMData();
-					updated = true;
+					if (updated) {
+						fft.realForward(PCM);
+					}
 					windowsRead++;
 					
 					//contemplate synchronization