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package javax.sound.midi;


/**
 * A <code>VoiceStatus</code> object contains information about the current
 * status of one of the voices produced by a {@link Synthesizer}.
 * <p>
 * MIDI synthesizers are generally capable of producing some maximum number of
 * simultaneous notes, also referred to as voices.  A voice is a stream
 * of successive single notes, and the process of assigning incoming MIDI notes to
 * specific voices is known as voice allocation.
 * However, the voice-allocation algorithm and the contents of each voice are
 * normally internal to a MIDI synthesizer and hidden from outside view.  One can, of
 * course, learn from MIDI messages which notes the synthesizer is playing, and
 * one might be able deduce something about the assignment of notes to voices.
 * But MIDI itself does not provide a means to report which notes a
 * synthesizer has assigned to which voice, nor even to report how many voices
 * the synthesizer is capable of synthesizing.
 * <p>
 * In Java Sound, however, a
 * <code>Synthesizer</code> class can expose the contents of its voices through its
 * {@link Synthesizer#getVoiceStatus() getVoiceStatus()} method.
 * This behavior is recommended but optional;
 * synthesizers that don't expose their voice allocation simply return a
 * zero-length array. A <code>Synthesizer</code> that does report its voice status
 * should maintain this information at
 * all times for all of its voices, whether they are currently sounding or
 * not.  In other words, a given type of <code>Synthesizer</code> always has a fixed
 * number of voices, equal to the maximum number of simultaneous notes it is
 * capable of sounding.
 * <p>
 * <A NAME="description_of_active"></A>
 * If the voice is not currently processing a MIDI note, it
 * is considered inactive.  A voice is inactive when it has
 * been given no note-on commands, or when every note-on command received has
 * been terminated by a corresponding note-off (or by an "all notes off"
 * message).  For example, this happens when a synthesizer capable of playing 16
 * simultaneous notes is told to play a four-note chord; only
 * four voices are active in this case (assuming no earlier notes are still playing).
 * Usually, a voice whose status is reported as active is producing audible sound, but this
 * is not always true; it depends on the details of the instrument (that
 * is, the synthesis algorithm) and how long the note has been going on.
 * For example, a voice may be synthesizing the sound of a single hand-clap.  Because
 * this sound dies away so quickly, it may become inaudible before a note-off
 * message is received.  In such a situation, the voice is still considered active
 * even though no sound is currently being produced.
 * <p>
 * Besides its active or inactive status, the <code>VoiceStatus</code> class
 * provides fields that reveal the voice's current MIDI channel, bank and
 * program number, MIDI note number, and MIDI volume.  All of these can
 * change during the course of a voice.  While the voice is inactive, each
 * of these fields has an unspecified value, so you should check the active
 * field first.
 *
 * @see Synthesizer#getMaxPolyphony
 * @see Synthesizer#getVoiceStatus
 *
 * @author David Rivas
 * @author Kara Kytle
 */

public class VoiceStatus {


    /**
     * Indicates whether the voice is currently processing a MIDI note.
     * See the explanation of
     * <A HREF="#description_of_active">active and inactive voices</A>.
     */
    public boolean active = false;


    /**
     * The MIDI channel on which this voice is playing.  The value is a
     * zero-based channel number if the voice is active, or
     * unspecified if the voice is inactive.
     *
     * @see MidiChannel
     * @see #active
     */
    public int channel = 0;


    /**
     * The bank number of the instrument that this voice is currently using.
     * This is a number dictated by the MIDI bank-select message; it does not
     * refer to a <code>SoundBank</code> object.
     * The value ranges from 0 to 16383 if the voice is active, and is
     * unspecified if the voice is inactive.
     * @see Patch
     * @see Soundbank
     * @see #active
     * @see MidiChannel#programChange(int, int)
     */
    public int bank = 0;


    /**
     * The program number of the instrument that this voice is currently using.
     * The value ranges from 0 to 127 if the voice is active, and is
     * unspecified if the voice is inactive.
     *
     * @see MidiChannel#getProgram
     * @see Patch
     * @see #active
     */
    public int program = 0;


    /**
     * The MIDI note that this voice is playing.  The range for an active voice
     * is from 0 to 127 in semitones, with 60 referring to Middle C.
     * The value is unspecified if the voice is inactive.
     *
     * @see MidiChannel#noteOn
     * @see #active
     */
    public int note = 0;


    /**
     * The current MIDI volume level for the voice.
     * The value ranges from 0 to 127 if the voice is active, and is
     * unspecified if the voice is inactive.
     * <p>
     * Note that this value does not necessarily reflect
     * the instantaneous level of the sound produced by this
     * voice; that level is the result of  many contributing
     * factors, including the current instrument and the
     * shape of the amplitude envelope it produces.
     *
     * @see #active
     */
    public int volume = 0;
}