Re: A Couple of Midi Tempo and TimeSig Questions
Re: A Couple of Midi Tempo and TimeSig Questions
- Subject: Re: A Couple of Midi Tempo and TimeSig Questions
- From: Peter Zegelin <email@hidden>
- Date: Thu, 15 Apr 2004 22:09:13 +1000
On Thursday, April 15, 2004, at 03:00 PM, Brian Willoughby wrote:
I believe that the theoretical maximum Tempo would be 60,000,000 BPM.
The
Standard MIDI File encodes a Tempo Meta Event in microseconds per
quarter-note,
as a 24-bit integer. The lowest Tempo would be 0.27962 BPM. However,
the
Tempo is also effectively modified by the Time Signature Meta Event,
which
includes a byte for "Clocks Per Metronome Click" [0-255] and "Notated
32nd-notes Per MIDI Quarter-Note" [0-255]. The math for that is left
to the
reader. I couldn't find the SMF spec on hand, and I cannot remember
if the
usec count is allowed to range from 1 to 16,777,216 as allowed by the
bits
allocated.
I never could figure out what all that "Notated 32nd-notes Per MIDI
Quarter-Note"
stuff meant so have basically ignored it for now. I hope it isnt
commonly used.
I realize that these limits are so large as to be of little help. The
only
good news is that the Tempo is not unbounded, although the allowed
range is
incredibly large compared to the practical user range.
Sounds like I better make it user settable just in case someone does
want to go a bit higher than say 500!
thanks for the info,
Peter
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