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Merge "BLE-MIDI: fix timestamps for sysex data" into rvc-dev

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TreeHugger Robot
2020-03-28 02:13:57 +00:00
committed by Android (Google) Code Review
parent 5c0b30caab 51aaf2e89e
commit 2682bcf618
1 changed files with 44 additions and 36 deletions
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80
media/packages/BluetoothMidiService/src/com/android/bluetoothmidiservice/BluetoothPacketDecoder.java
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@@ -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);
}
mBuffer[mBytesInBuffer++] = b;
}
}
if (dataCount > 0) {
try {
receiver.send(mBuffer, 0, dataCount, nanoTimestamp);
} catch (IOException e) {
// ???
}
}
flushOutput(receiver);
}
}