Add support for Bluetooth MIDI devices
The Bluetooth MIDI devices are handled in the BluetoothMidiService APK.
Apps wishing to connect to Bluetooth MIDI devices call MidiManager.openBluetoothDevice()
which binds to BluetoothMidiService in a similar way as virtual devices are implemented.
Change-Id: Ie3fbca757928fd7873a009f9bf9e0ce0be487da6
diff --git a/media/packages/BluetoothMidiService/src/com/android/bluetoothmidiservice/BluetoothPacketDecoder.java b/media/packages/BluetoothMidiService/src/com/android/bluetoothmidiservice/BluetoothPacketDecoder.java
new file mode 100644
index 0000000..c5bfb5f
--- /dev/null
+++ b/media/packages/BluetoothMidiService/src/com/android/bluetoothmidiservice/BluetoothPacketDecoder.java
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * 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.android.bluetoothmidiservice;
+
+import android.media.midi.MidiReceiver;
+import android.util.Log;
+
+import java.io.IOException;
+
+/**
+ * This is an abstract base class that decodes a packet buffer and passes it to a
+ * {@link android.media.midi.MidiReceiver}
+ */
+public class BluetoothPacketDecoder extends PacketDecoder {
+
+ private static final String TAG = "BluetoothPacketDecoder";
+
+ private final byte[] mBuffer;
+
+ private final int TIMESTAMP_MASK_HIGH = 0x1F80;
+ private final int TIMESTAMP_MASK_LOW = 0x7F;
+ private final int HEADER_TIMESTAMP_MASK = 0x3F;
+
+ public BluetoothPacketDecoder(int maxPacketSize) {
+ mBuffer = new byte[maxPacketSize];
+ }
+
+ @Override
+ public void decodePacket(byte[] buffer, MidiReceiver receiver) {
+ int length = buffer.length;
+
+ // NOTE his code allows running status across packets,
+ // although the specification does not allow that.
+
+ if (length < 1) {
+ Log.e(TAG, "empty packet");
+ return;
+ }
+ byte header = buffer[0];
+ if ((header & 0xC0) != 0x80) {
+ Log.e(TAG, "packet does not start with header");
+ return;
+ }
+
+ // shift bits 0 - 5 to bits 7 - 12
+ int timestamp = (header & HEADER_TIMESTAMP_MASK) << 7;
+ boolean lastWasTimestamp = false;
+ int dataCount = 0;
+ int previousLowTimestamp = 0;
+
+ // iterate through the rest of the packet, separating MIDI data from timestamps
+ for (int i = 1; i < buffer.length; i++) {
+ byte b = buffer[i];
+
+ if ((b & 0x80) != 0 && !lastWasTimestamp) {
+ lastWasTimestamp = true;
+ int lowTimestamp = b & TIMESTAMP_MASK_LOW;
+ int newTimestamp = (timestamp & TIMESTAMP_MASK_HIGH) | lowTimestamp;
+ if (lowTimestamp < previousLowTimestamp) {
+ newTimestamp = (newTimestamp + 0x0080) & TIMESTAMP_MASK_HIGH;
+ }
+ previousLowTimestamp = lowTimestamp;
+
+ if (newTimestamp != timestamp) {
+ if (dataCount > 0) {
+ // send previous message separately since it has a different timestamp
+ try {
+ // FIXME use sendWithTimestamp
+ receiver.send(mBuffer, 0, dataCount);
+ } catch (IOException e) {
+ // ???
+ }
+ dataCount = 0;
+ }
+ }
+ timestamp = newTimestamp;
+ } else {
+ lastWasTimestamp = false;
+ mBuffer[dataCount++] = b;
+ }
+ }
+
+ if (dataCount > 0) {
+ try {
+ // FIXME use sendWithTimestamp
+ receiver.send(mBuffer, 0, dataCount);
+ } catch (IOException e) {
+ // ???
+ }
+ }
+ }
+}