AudioUtils.java

//    This file is part of Penn TotalRecall <http://memory.psych.upenn.edu/TotalRecall>.
//
//    TotalRecall is free software: you can redistribute it and/or modify
//    it under the terms of the GNU General Public License as published by
//    the Free Software Foundation, version 3 only.
//
//    TotalRecall is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU General Public License for more details.
//
//    You should have received a copy of the GNU General Public License
//    along with TotalRecall.  If not, see <http://www.gnu.org/licenses/>.

package util;

import java.io.IOException;

import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;

public class AudioUtils {
	
	/**
	 * Creates an <code>AudioInputStream</code> that iterates only over the desired frames.
	 * 
	 * The start and end frames are global variables.
	 * 
	 * @param format The format of the desired <code>AudioInputStream</code>
	 * @param originalAis The <code>AudioInputStream</code> to be "cropped"
	 * @return An <code>AudioInputStream</code> cropped from the original one
	 * @throws IOException If an I/O exception occurs
	 */
	protected AudioInputStream createAudioInputStream(AudioFormat format, AudioInputStream originalAis, long startFrame, long endFrame) throws IOException {
		AudioInputStream outputAis = AudioSystem.getAudioInputStream(format, originalAis);
		//skip to desired frame
		if(startFrame > 0 || endFrame > 0) {
			long bytesToSkip = startFrame * 2;
			if(bytesToSkip > outputAis.available()) {
				System.err.println("you are trying to skip over more bytes than are available");
			}
			else {
				if(startFrame > 0) {
					synchronized(outputAis) {
						long framesActuallySkipped = outputAis.skip(bytesToSkip);
						if(framesActuallySkipped != bytesToSkip) {
							System.err.println(framesActuallySkipped + "/" + bytesToSkip + " bytes actually skipped");
						}
					}
				}
				if(endFrame > 0) {
					long length = 0;
					if(endFrame < 0) {
						length = originalAis.available() - bytesToSkip;
					}
					else {
						length = endFrame - startFrame;
					}
					outputAis = new AudioInputStream(outputAis, outputAis.getFormat(), length);
				}
			}
		}		
		return outputAis;
	}
}