[linux-audio-dev] Basic MIDI question

[Clemens Ladisch]

Ari Kauppi wrote:
> On Wed, 26 Jul 2006, Jens M Andreasen wrote:
> 
> >     if(runningStatus == NOTE_ON || runningStatus == NOTE_OFF)
> 
> If you plan to receive messages from other channels than 0 you have to 
> use (runningStatus & 0xF0) instead of the full runningStatus and perhaps 
> check for (runningStaus & 0x0F) == receiveChannel..

Okay, here is my entry to the Official LAD MIDI Parser Contest 2006:

void handleByte(u8 byte)
{
	/* in a driver, these static variables should go into some struct: */
	static enum {
		STATE_UNKNOWN, /* not a note command */
		STATE_NOTE1,   /* expecting 1st data byte (note) */
		STATE_NOTE2,   /* expecting 2nd data byte (velocity) */
	} state = STATE_UNKNOWN;
	static u8 command;
	static u8 note;

	if (byte >= 0xf8) /* real-time command */
		;
	else if (byte & 0x80) { /* status byte */
		command = byte;
		/* note-on or note-off? */
		state = (byte & 0xf0) <= 0x90 ? STATE_NOTE1 : STATE_UNKNOWN;
	} else { /* data byte */
		if (state == STATE_NOTE1) {
			note = byte;
			state = STATE_NOTE2;
		} else if (state == STATE_NOTE2) {
			if ((command & 0xf0) == 0x90 && byte > 0) {
				/* note on */
			} else {
				/* note off */
			}
			state = STATE_NOTE1;
		}
	}
}


Regards,
Clemens