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: William Stewart <email@hidden>
- Date: Thu, 15 Apr 2004 11:06:24 -0700
On 14/04/2004, at 8:02 PM, Brian Willoughby wrote:
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Peter,
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I believe that the theoretical maximum Tempo would be 60,000,000 BPM.
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The
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Standard MIDI File encodes a Tempo Meta Event in microseconds per
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quarter-note,
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as a 24-bit integer. The lowest Tempo would be 0.27962 BPM. However,
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the
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Tempo is also effectively modified by the Time Signature Meta Event,
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which
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includes a byte for "Clocks Per Metronome Click" [0-255] and "Notated
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32nd-notes Per MIDI Quarter-Note" [0-255]. The math for that is left
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to the
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reader. I couldn't find the SMF spec on hand, and I cannot remember
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if the
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usec count is allowed to range from 1 to 16,777,216 as allowed by the
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bits
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allocated.
No. Tempo events are not modified by Time Sig events. Time Sig events
are purely informational, and have no baring on Tempo. The fields you
are describing are how you would translate the basic time meter used in
a midi file when you *display* or otherwise use the Time Sig events for
some other nefarious (highly technical term) purpose.
As for limits, well, until Coltrane and Bird came along, 40 -> 208
seemed to do everyone else just fine :-)
Bill
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I realize that these limits are so large as to be of little help. The
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only
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good news is that the Tempo is not unbounded, although the allowed
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range is
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incredibly large compared to the practical user range.
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>
Brian Willoughby
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Sound Consulting
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>
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Begin forwarded message:
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Date: Thu, 15 Apr 2004 10:59:26 +1000
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Subject: Re: A Couple of Midi Tempo and TimeSig Questions
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From: Peter Zegelin <email@hidden>
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To: email@hidden
>
>
>> Also is there any default maximum Tempo value? I'm generating a
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>> fairly standard squiggly line type Tempo view and was wondering what
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>> a
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>> reasonable maximum might be. At the moment I am actually calculating
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>> the maximum tempo for the current file and using that, but is there
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>> some sort of standard?
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[...]
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However my question was more about what would be a reasonable maximum
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for display purposes. All the other events that are commonly displayed
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(and edited) as a squiggly line (not sure of the correct term here!)
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have defined minimum/maximum values - whereas Tempo events don't, and I
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was just wondering if there is a commonly used value (say 500).
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