1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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24 */
25
26 package javax.sound.midi;
27
28 /**
29 * A {@code VoiceStatus} object contains information about the current status of
30 * one of the voices produced by a {@link Synthesizer}.
31 * <p>
32 * MIDI synthesizers are generally capable of producing some maximum number of
33 * simultaneous notes, also referred to as voices. A voice is a stream of
34 * successive single notes, and the process of assigning incoming MIDI notes to
35 * specific voices is known as voice allocation. However, the voice-allocation
36 * algorithm and the contents of each voice are normally internal to a MIDI
37 * synthesizer and hidden from outside view. One can, of course, learn from MIDI
38 * messages which notes the synthesizer is playing, and one might be able deduce
39 * something about the assignment of notes to voices. But MIDI itself does not
40 * provide a means to report which notes a synthesizer has assigned to which
41 * voice, nor even to report how many voices the synthesizer is capable of
42 * synthesizing.
43 * <p>
44 * In Java Sound, however, a {@code Synthesizer} class can expose the contents
45 * of its voices through its
46 * {@link Synthesizer#getVoiceStatus() getVoiceStatus()} method. This behavior
47 * is recommended but optional; synthesizers that don't expose their voice
48 * allocation simply return a zero-length array. A {@code Synthesizer} that does
49 * report its voice status should maintain this information at all times for all
50 * of its voices, whether they are currently sounding or not. In other words, a
51 * given type of {@code Synthesizer} always has a fixed number of voices, equal
52 * to the maximum number of simultaneous notes it is capable of sounding.
53 * <p>
54 * <a id="description_of_active"></a> If the voice is not currently processing
55 * a MIDI note, it is considered inactive. A voice is inactive when it has been
56 * given no note-on commands, or when every note-on command received has been
57 * terminated by a corresponding note-off (or by an "all notes off" message).
58 * For example, this happens when a synthesizer capable of playing 16
59 * simultaneous notes is told to play a four-note chord; only four voices are
60 * active in this case (assuming no earlier notes are still playing). Usually, a
61 * voice whose status is reported as active is producing audible sound, but this
62 * is not always true; it depends on the details of the instrument (that is, the
63 * synthesis algorithm) and how long the note has been going on. For example, a
64 * voice may be synthesizing the sound of a single hand-clap. Because this sound
65 * dies away so quickly, it may become inaudible before a note-off message is
66 * received. In such a situation, the voice is still considered active even
67 * though no sound is currently being produced.
68 * <p>
69 * Besides its active or inactive status, the {@code VoiceStatus} class provides
70 * fields that reveal the voice's current MIDI channel, bank and program number,
71 * MIDI note number, and MIDI volume. All of these can change during the course
72 * of a voice. While the voice is inactive, each of these fields has an
73 * unspecified value, so you should check the active field first.
74 *
75 * @author David Rivas
76 * @author Kara Kytle
77 * @see Synthesizer#getMaxPolyphony
78 * @see Synthesizer#getVoiceStatus
79 */
80 public class VoiceStatus {
81
82 /**
83 * Indicates whether the voice is currently processing a MIDI note. See the
84 * explanation of
85 * <a HREF="#description_of_active">active and inactive voices</a>.
86 */
87 public boolean active = false;
88
89 /**
90 * The MIDI channel on which this voice is playing. The value is a
91 * zero-based channel number if the voice is active, or unspecified if the
92 * voice is inactive.
93 *
94 * @see MidiChannel
95 * @see #active
96 */
97 public int channel = 0;
98
99 /**
100 * The bank number of the instrument that this voice is currently using.
101 * This is a number dictated by the MIDI bank-select message; it does not
102 * refer to a {@code SoundBank} object. The value ranges from 0 to 16383 if
103 * the voice is active, and is unspecified if the voice is inactive.
104 *
105 * @see Patch
106 * @see Soundbank
107 * @see #active
108 * @see MidiChannel#programChange(int, int)
109 */
110 public int bank = 0;
111
112 /**
113 * The program number of the instrument that this voice is currently using.
114 * The value ranges from 0 to 127 if the voice is active, and is unspecified
115 * if the voice is inactive.
116 *
117 * @see MidiChannel#getProgram
118 * @see Patch
119 * @see #active
120 */
121 public int program = 0;
122
123 /**
124 * The MIDI note that this voice is playing. The range for an active voice
125 * is from 0 to 127 in semitones, with 60 referring to Middle C. The value
126 * is unspecified if the voice is inactive.
127 *
128 * @see MidiChannel#noteOn
129 * @see #active
130 */
131 public int note = 0;
132
133 /**
134 * The current MIDI volume level for the voice. The value ranges from 0 to
135 * 127 if the voice is active, and is unspecified if the voice is inactive.
136 * <p>
137 * Note that this value does not necessarily reflect the instantaneous level
138 * of the sound produced by this voice; that level is the result of many
139 * contributing factors, including the current instrument and the shape of
140 * the amplitude envelope it produces.
141 *
142 * @see #active
143 */
144 public int volume = 0;
145 }