Re: Sysex MIDI Packets
Re: Sysex MIDI Packets
- Subject: Re: Sysex MIDI Packets
- From: Doug Wyatt <email@hidden>
- Date: Tue, 10 Feb 2004 12:09:22 -0800
On Feb 10, 2004, at 0:09, Rib Rdb wrote:
Another developer on my project is interpretting the documentation
differently than I am on what can be in a MIDIPacket, and I wanted to
try to figure out what's right. Our confusion is with Sysex messages
that are mixed with realtime messages. We're trying to figure out if
it would be possible to recieve a packet with data like this:
{ 0xf0, 0, 1, 2, 0xfe, 3, 5, 6, 7, 8, 0xf7 }
or maybe two packets like
{ 0xf0, 0, 1, 2}, { 0xfe, 3, 5, 6, 7, 8, 0xf7 }
or if it will always come with the realtime message in it's own
packet:
{ 0xf0, 0, 1, 2 }, { 0xfe }, { 3, 5, 6, 7, 8, 0xf7 }
thanks for your help.
The latter, with the realtime message in its own packet. If any one is
producing packets differently, it's a bug.
The doc in question (MIDIPacket.data):
A variable-length stream of MIDI messages. Running status
is not allowed. In the case of system-exclusive
messages, a packet may only contain a single message, or
portion of one, with no other MIDI events.
The MIDI messages in the packet must always be complete,
except for system-exclusive.
A realtime message is a separate message -- it may not occur in the
same packet as a system-exclusive message; it must be in its own packet
(which makes particular sense if you consider a device that is sending
clock at the same time it is dumping sysex -- by requiring the F8 to be
in a separate packet, it then gets a timestamp).
Doug
--
Doug Wyatt
Core Audio, Apple
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