Re: MIDI Delta-Time to milliseconds?

At 03:53 AM 2004-10-19, Christian Renz wrote:
>I'm having difficulties to find an exact definition of "MIDI delta time" 
>as used in standard MIDI files. How can I convert these delta times to 
>milliseconds; do I need to factor in any other control messages/SMPTE 
>settings/.... ?

What I remember is this:
If I want one quarter-note (96 delta-time units) to be a half-second, I 
start a MIDI::Simple program with this:

  set_tempo 500000;  # 1 qn => .5 seconds (500,000 microseconds)


As to what complexity this avoids?  I think the conversion of ticks to 
actual real time involves the Ticks parameter in the MIDI header, and the 
current set_tempo value.  I don't think the time-signature in involved, but 
I can't swear to that.  And there could even be another level of 
indirection lurking in the MIDI spec somewhere; my memory is hazy, and 
hopefully someone else knows.

An additional caveat:
I once made a MIDI version of John Cage's /4'33"/, a piece which, as the 
title expresses, should really last exactly four minutes and thirty-three 
seconds.  But I distinctly remember getting a piece of email (although only 
one) from someone whose MIDI player said it was a different length, like 
five minutes ten seconds.  So, buggy MIDI players have existed!
But that was ages ago, and I've never heard anything like that since, so 
hopefully you won't run into anything like that these days.

--
Sean M. Burke    http://search.cpan.org/~sburke/