Re: Questions on data in MIDIPackets
Re: Questions on data in MIDIPackets
- Subject: Re: Questions on data in MIDIPackets
- From: Doug Wyatt <email@hidden>
- Date: Mon, 11 Feb 2002 23:04:10 -0500
Herbie, I agree with Brian and will document things that way.
Doug
On Monday, February 11, 2002, at 07:11 , Brian Willoughby wrote:
Herbie Robinson <email@hidden> wrote:
[ I already added a bug asking for clarification as to whether the
[ time-stamp applies to the beginning or the end of the packet. If
[ no clarification ever comes, then I would assume the time-stamp
[ applies to the END of the packet (i.e. the instant the last byte
[ has finished transmitting), because that's when any real hardware
[ will be able to start responding to the last event in the packet.
I have to disagree for a couple of reasons:
First of all, I can think of a few examples where a MIDI device can
either
completely or at least partially respond to a message before all bytes
have
arrived - e.g. a Note Off event directed to a voice which does not
respond to
Note-off Velocity could easily respond to the message before the third
byte
arrives. It's true that the simplest MIDI firmware might wait for all
bytes
before starting to respond, but more aggressive devices could get very
creative
about responding earlier to specific types of messages - and therefore
the
timing of the beginning of the packet should be the focus.
More importantly, the timing of the beginning of the packet more closely
correlates to a physical event, while the end of the packet is merely an
artifact of the transmission medium, and will vary from interface to
interface.
Most MIDI events originate from a Human Interface Device, and so the
time-stamp of the beginning of the packet most closely reflects the
real event.
Most musicians probably don't care about preserving the latency
introduced by
multi-byte packets on traditional MIDI, and sequencers certainly
shouldn't
preserve (slow) MIDI timings when playing back on higher resolution
interfaces
such as USB.
Brian Willoughby
Sound Consulting
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