SampleBuffer.java

/*
 *  Copyright (C) 2011 in-somnia
 * 
 *  This file is part of JAAD.
 * 
 *  JAAD is free software; you can redistribute it and/or modify it 
 *  under the terms of the GNU Lesser General Public License as 
 *  published by the Free Software Foundation; either version 3 of the 
 *  License, or (at your option) any later version.
 *
 *  JAAD 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 Lesser General 
 *  Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library.
 *  If not, see <http://www.gnu.org/licenses/>.
 */
package net.sourceforge.jaad.aac;

/**
 * The SampleBuffer holds the decoded AAC frame. It contains the raw PCM data
 * and its format.
 * @author in-somnia
 */
public class SampleBuffer {

	private int sampleRate, channels, bitsPerSample;
	private double length, bitrate, encodedBitrate;
	private byte[] data;
	private boolean bigEndian;

	public SampleBuffer() {
		data = new byte[0];
		sampleRate = 0;
		channels = 0;
		bitsPerSample = 0;
		bigEndian = true;
	}

	/**
	 * Returns the buffer's PCM data.
	 * @return the audio data
	 */
	public byte[] getData() {
		return data;
	}

	/**
	 * Returns the data's sample rate.
	 * @return the sample rate
	 */
	public int getSampleRate() {
		return sampleRate;
	}

	/**
	 * Returns the number of channels stored in the data buffer.
	 * @return the number of channels
	 */
	public int getChannels() {
		return channels;
	}

	/**
	 * Returns the number of bits per sample. Usually this is 16, meaning a
	 * sample is stored in two bytes.
	 * @return the number of bits per sample
	 */
	public int getBitsPerSample() {
		return bitsPerSample;
	}

	/**
	 * Returns the length of the current frame in seconds.
	 * length = samplesPerChannel / sampleRate
	 * @return the length in seconds
	 */
	public double getLength() {
		return length;
	}

	/**
	 * Returns the bitrate of the decoded PCM data.
	 * <code>bitrate = (samplesPerChannel * bitsPerSample) / length</code>
	 * @return the bitrate
	 */
	public double getBitrate() {
		return bitrate;
	}

	/**
	 * Returns the AAC bitrate of the current frame.
	 * @return the AAC bitrate
	 */
	public double getEncodedBitrate() {
		return encodedBitrate;
	}

	/**
	 * Indicates the endianness for the data.
	 * 
	 * @return true if the data is in big endian, false if it is in little endian
	 */
	public boolean isBigEndian() {
		return bigEndian;
	}

	/**
	 * Sets the endianness for the data.
	 * 
	 * @param bigEndian if true the data will be in big endian, else in little 
	 * endian
	 */
	public void setBigEndian(boolean bigEndian) {
		if(bigEndian!=this.bigEndian) {
			byte tmp;
			for(int i = 0; i<data.length; i += 2) {
				tmp = data[i];
				data[i] = data[i+1];
				data[i+1] = tmp;
			}
			this.bigEndian = bigEndian;
		}
	}

	public void setData(byte[] data, int sampleRate, int channels, int bitsPerSample, int bitsRead) {
		this.data = data;
		this.sampleRate = sampleRate;
		this.channels = channels;
		this.bitsPerSample = bitsPerSample;

		if(sampleRate==0) {
			length = 0;
			bitrate = 0;
			encodedBitrate = 0;
		}
		else {
			final int bytesPerSample = bitsPerSample/8; //usually 2
			final int samplesPerChannel = data.length/(bytesPerSample*channels); //=1024
			length = (double) samplesPerChannel/(double) sampleRate;
			bitrate = (double) (samplesPerChannel*bitsPerSample*channels)/length;
			encodedBitrate = (double) bitsRead/length;
		}
	}
}