Merge "BLE-MIDI: fix timestamps for sysex data" (731a5b45) · Commits · e / os / android_frameworks_base

media/packages/BluetoothMidiService/src/com/android/bluetoothmidiservice/BluetoothPacketDecoder.java

+44 −36

Original line number	Diff line number	Diff line
		@@ -22,24 +22,41 @@ 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}
		* This is an abstract base class that decodes a BLE-MIDI 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 int mBytesInBuffer;
		private MidiBtleTimeTracker mTimeTracker;

		private final int TIMESTAMP_MASK_HIGH = 0x1F80;
		private final int TIMESTAMP_MASK_LOW = 0x7F;
		private final int HEADER_TIMESTAMP_MASK = 0x3F;
		private int mLowTimestamp;
		private long mNanoTimestamp;

		private static final int TIMESTAMP_MASK_HIGH = 0x1F80; // top 7 bits
		private static final int TIMESTAMP_MASK_LOW = 0x7F; // bottom 7 bits
		private static final int HEADER_TIMESTAMP_MASK = 0x3F; // bottom 6 bits

		public BluetoothPacketDecoder(int maxPacketSize) {
		mBuffer = new byte[maxPacketSize];
		}

		private void flushOutput(MidiReceiver receiver) {
		if (mBytesInBuffer > 0) {
		try {
		receiver.send(mBuffer, 0, mBytesInBuffer, mNanoTimestamp);
		} catch (IOException e) {
		// ???
		}
		mBytesInBuffer = 0;
		}
		}

		// NOTE: this code allows running status across packets,
		// although the specification does not allow that.
		@Override
		public void decodePacket(byte[] buffer, MidiReceiver receiver) {
		if (mTimeTracker == null) {
		@@ -47,14 +64,11 @@ public class BluetoothPacketDecoder extends PacketDecoder {
		}

		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");
		@@ -64,52 +78,46 @@ public class BluetoothPacketDecoder extends PacketDecoder {
		// shift bits 0 - 5 to bits 7 - 12
		int highTimestamp = (header & HEADER_TIMESTAMP_MASK) << 7;
		boolean lastWasTimestamp = false;
		int dataCount = 0;
		int previousLowTimestamp = 0;
		long nanoTimestamp = 0;
		int currentTimestamp = 0;
		int currentTimestamp = highTimestamp \| mLowTimestamp;

		// iterate through the rest of the packet, separating MIDI data from timestamps
		// Iterate through the rest of the packet, separating MIDI data from timestamps.
		for (int i = 1; i < buffer.length; i++) {
		byte b = buffer[i];

		// Is this a timestamp byte?
		if ((b & 0x80) != 0 && !lastWasTimestamp) {
		lastWasTimestamp = true;
		int lowTimestamp = b & TIMESTAMP_MASK_LOW;
		if (lowTimestamp < previousLowTimestamp) {
		mLowTimestamp = b & TIMESTAMP_MASK_LOW;

		// If the low timestamp byte wraps within the packet then
		// increment the high timestamp byte.
		if (mLowTimestamp < previousLowTimestamp) {
		highTimestamp = (highTimestamp + 0x0080) & TIMESTAMP_MASK_HIGH;
		}
		previousLowTimestamp = lowTimestamp;
		previousLowTimestamp = mLowTimestamp;

		int newTimestamp = highTimestamp \| lowTimestamp;
		// If the timestamp advances then send any pending data.
		int newTimestamp = highTimestamp \| mLowTimestamp;
		if (newTimestamp != currentTimestamp) {
		if (dataCount > 0) {
		// send previous message separately since it has a different timestamp
		try {
		receiver.send(mBuffer, 0, dataCount, nanoTimestamp);
		} catch (IOException e) {
		// ???
		}
		dataCount = 0;
		}
		// Send previous message separately since it has a different timestamp.
		flushOutput(receiver);
		currentTimestamp = newTimestamp;
		}

		// calculate nanoTimestamp
		// Calculate MIDI nanosecond timestamp from BLE timestamp.
		long now = System.nanoTime();
		nanoTimestamp = mTimeTracker.convertTimestampToNanotime(currentTimestamp, now);
		mNanoTimestamp = mTimeTracker.convertTimestampToNanotime(currentTimestamp, now);
		} else {
		lastWasTimestamp = false;
		mBuffer[dataCount++] = b;
		// Flush if full before adding more data.
		if (mBytesInBuffer == mBuffer.length) {
		flushOutput(receiver);
		}
		}

		if (dataCount > 0) {
		try {
		receiver.send(mBuffer, 0, dataCount, nanoTimestamp);
		} catch (IOException e) {
		// ???
		mBuffer[mBytesInBuffer++] = b;
		}
		}

		flushOutput(receiver);
		}
		}