MidiBufferHelpers::findActualEventLength() and 'MIDI System Reset'


#1

According to the MIDI Standard, a ‘MIDI System Reset’ message is 1 byte message with a status byte of 0xFF.

However, when MidiBufferHelpers::findActualEventLength() encounters a status byte of 0xFF it reads it as a variable length message and seems to return garbage:

else if (byte == 0xff)
{
    s32 n;
    const s32 bytesLeft = MidiMessage::readVariableLengthVal (data + 1, n);
    size = jmin (maxBytes, n + 2 + bytesLeft);
}

Any idea what the intention is here? Is 0xFF used as some special sentinel value in MidiBuffer?


#2

OK, after a bit more research I found this:

Note on status byte 0xFF

The reset message (a system realtime message) carries the same status byte as a meta message: 0xFF. By convention, the MIDI reset message is never placed in MIDI files but is only sent over MIDI ports upon a request by the user. Thus, if a MIDI device receives the status byte 0xFF over a MIDI port, the device will interpret it as a “reset” message. If the MIDI device reads the status byte 0xFF from within some MIDI file, the device will interpret the message as a meta message.

So the answer seems to be to never add a MIDI System Reset message to a MidiBuffer.