[sdiy] Midi problems

[Andre Majorel]

On 2002-04-03 23:37 +0100, Paul Maddox wrote:

> simple trick, if the MSB is set, REMEMBER the byte (call it running_status)
> if you get ANY other byte with the MSB set, forget the running_status byte
> as the data that follows is for some other channel.

Some bytes with the MSB set don't count for running status.

> watch out for CLOCK data though :-) it can arrive at ANY point.. so if you
> dont plan on useing it make sure you have a filter setup, so if midi clock
> arrives it simply gets ignored and nothing is done with it (dont change the
> counter value either!)

Yes, and not only clock !

Status bytes F8h - FFh (as you said clock, but also tick, start,
continue, stop, sense and reset) are called real time messages.
They have no data byte and they have two unique properties :
- they can intervene *inside* other messages,
- they're not eligible for running status.

So the correct way to handle running status is :

  unsigned char running_status = 0;
  for (;;)
  {
    ...
    unsigned char b = getc (midi_fp);
    ...
    if (b >= 0x80 && b < 0xf8)
      running_status = b;
    ...
  }

-- 
André Majorel <amajorel at teaser.fr>
http://www.teaser.fr/~amajorel/