/*
 * 11/19/04		1.0 moved to LGPL.
 * 29/01/00		Initial version. mdm@techie.com
 *-----------------------------------------------------------------------
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as published
 *   by the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program 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 Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *----------------------------------------------------------------------
 */

package javazoom.jl.player;

import javazoom.jl.decoder.Decoder;
import javazoom.jl.decoder.JavaLayerException;

/**
 * The <code>AudioDevice</code> interface provides an abstraction for a device
 * capable of sounding audio samples. Samples are written to the device wia the
 * write() method. The device assumes that these samples are signed 16-bit
 * samples taken at the output frequency of the decoder. If the decoder outputs
 * more than one channel, the samples for each channel are assumed to appear
 * consecutively, with the lower numbered channels preceeding higher-numbered
 * channels. E.g. if there are two channels, the samples will appear in this
 * order:
 * 
 * <pre>
 * <code>
 * 
 * 	l0, r0, l1, r1, l2, r2...
 * 
 * where 
 * l<i>x</i> indicates the <i>x</i>th sample on channel 0
 *  r<i>x</i> indicates the <i>x</i>th sample on channel 1
 * </code>
 * </pre>
 * 
 * @since 0.0.8
 * @author Mat McGowan
 */
public interface AudioDevice
{

	/**
	 * Prepares the AudioDevice for playback of audio samples.
	 * 
	 * @param decoder
	 *            The decoder that will be providing the audio samples.
	 * 
	 *            If the audio device is already open, this method returns
	 *            silently.
	 * 
	 */
	public void open(Decoder decoder) throws JavaLayerException;

	/**
	 * Retrieves the open state of this audio device.
	 * 
	 * @return <code>true</code> if this audio device is open and playing audio
	 *         samples, or <code>false</code> otherwise.
	 */
	public boolean isOpen();

	/**
	 * Writes a number of samples to this <code>AudioDevice</code>.
	 * 
	 * @param samples
	 *            The array of signed 16-bit samples to write to the audio
	 *            device.
	 * @param offs
	 *            The offset of the first sample.
	 * @param len
	 *            The number of samples to write.
	 * 
	 *            This method may return prior to the samples actually being
	 *            played by the audio device.
	 */
	public void write(short[] samples, int offs, int len) throws JavaLayerException;

	/**
	 * Closes this audio device. Any currently playing audio is stopped as soon
	 * as possible. Any previously written audio data that has not been heard is
	 * discarded.
	 * 
	 * The implementation should ensure that any threads currently blocking on
	 * the device (e.g. during a <code>write</code> or <code>flush</code>
	 * operation should be unblocked by this method.
	 */
	public void close();

	/**
	 * Blocks until all audio samples previously written to this audio device
	 * have been heard.
	 */
	public void flush();

	/**
	 * Retrieves the current playback position in milliseconds.
	 */
	public int getPosition();
}