1 files changed, 59 insertions, 0 deletions
diff --git a/src/com/jsyn/midi/MidiConstants.java b/src/com/jsyn/midi/MidiConstants.java
new file mode 100644
index 0000000..dae9390
--- /dev/null
+++ b/src/com/jsyn/midi/MidiConstants.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2010 Phil Burk, Mobileer Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.jsyn.midi;
+
+/**
+ * Constants that define the MIDI standard.
+ * 
+ * @author Phil Burk (C) 2010 Mobileer Inc
+ */
+public class MidiConstants {
+    // Basic commands.
+    public static final int NOTE_OFF = 0x80;
+    public static final int NOTE_ON = 0x90;
+    public static final int POLYPHONIC_AFTERTOUCH = 0xA0;
+    public static final int CONTROL_CHANGE = 0xB0;
+    public static final int PROGRAM_CHANGE = 0xC0;
+    public static final int CHANNEL_AFTERTOUCH = 0xD0;
+    public static final int PITCH_BEND = 0xE0;
+    public static final int SYSTEM_COMMON = 0xF0;
+
+    public static final int PITCH_BEND_CENTER = 8192;
+
+    public static final String PITCH_NAMES[] = {
+            "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"
+    };
+
+    /**
+     * Calculate frequency in Hertz based on MIDI pitch. Middle C is 60.0. You can use fractional
+     * pitches so 60.5 would give you a pitch half way between C and C#.
+     */
+    static final double CONCERT_A_FREQUENCY = 440.0;
+    static final double CONCERT_A_PITCH = 69.0;
+
+    public static double convertPitchToFrequency(double pitch) {
+        return CONCERT_A_FREQUENCY * Math.pow(2.0, ((pitch - CONCERT_A_PITCH) / 12.0));
+    }
+
+    /**
+     * Calculate MIDI pitch based on frequency in Hertz. Middle C is 60.0.
+     */
+    public static double convertFrequencyToPitch(double frequency) {
+        return CONCERT_A_PITCH + (12 * Math.log(frequency / CONCERT_A_FREQUENCY) / Math.log(2.0));
+    }
+
+}