Time signature conventions?

Discussion in 'alt.music.midi' started by Michael, Aug 29, 2003.

  1. Michael

    Michael Guest


    I'm working on a midi sequencer, and am trying to determine the best way to
    handle time signature messages in a midi file. In particular, how to
    interpret the "bb" param of the time sig meta-event, as described in the
    midi spec. This is the param that defines "the number of notated 32nd notes
    in what MIDI thinks of as a quarter note (24 MIDI Clocks)".

    I've been testing the behavior of Cakewalk Sonar (2.1), Pro Tools Free for
    Windows and Emagic Logic 5.5 on OS 9. Cakewalk and Logic always seem to
    disregard the "bb" paramter of the time signature. I've tested with time
    signature of 4/4, 6/8 and 4/16 with different values for the "bb" param, but
    they always play back with the tempo relative to a musical quarter note.
    Technically, if I define, for example, the "bb" param as 4, the tempo should
    be relative to an 1/8 note and not a 1/4 note. In Pro Tools, the files all
    open up with the quarter note taking the beat for tempo's sake no matter
    what the time signature "bb" value, but it can be manually overridden. In
    addition, the midi clock output is always relative to a musical quarter note
    as well, ie 24 clocks. In Pro Tools, if I change the note value that takes
    the tempo, the clock count is _still_ 24 / musical quarter note, which then
    makes things goofy, I think.

    So is this some sort of de facto standard way of treating tempo of midi
    files? ie to ignore the "bb" param?

    Also, less importantly, Cakewalk and Logic ignore the "cc" param of the time
    sig which defines the number of midi clocks per metrenome click, whereas Pro
    Tools Free seems to honor it, albeit with one exception I find which is
    possibly a bug.

    Does anyone have experience with this, or maybe know of a detailed
    discussion I could reference?

    Many thanks,

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