[music-dsp] Info about SMF Files
Ravi Kiran Chivukula
ravikiranc at gmail.com
Sun Aug 22 11:16:17 EDT 2004
I am trying to develop a parser for SMF files for use in a MIDI
software synthesizer. I have some doubts regarding the SMF file
1. As per my understanding if the 'division' word in the MThd chunk
indicates 'ticks per quarter note' there will be a corresponding 'Set
Tempo' meta event in the MTrk chunk. If the 'division' word contains
SMPTE time code there will be a corresponding 'SMPTE Offset' meta
event in the MTrk chunk. With the above information I have the
complete timing information. If so what will be the use of MIDI
quarter frame messages? Will these messages never occur in SMF files?
If they occur how should a synthesizer handle them?
2. Similarly do system real time messages (midi timing clock, start,
stop etc) ever occur in an SMF file? Since they are used for
synchronising I feel they won't be useful for a synthesizer. How
should they be treated if they do occur? I also read somewhere that
song position pointer message will be redundant if we use MIDI time
code. Is this true?
3. What is the importance of 'Time Signature' meta event? What is the
importance of metronome click and what are these notated 32nd notes?
Where do I use signatures like 4/4 time etc? I know the meaning of
these signatures but not how to use them.
4. Similarly what is the importance of 'Key Signature' meta event?
5. Can tempo be changed at any time in either format 0 or 1 files? In
the specification it is said that for a format 1 file the tempo map
must be stored in the first track. If so, how can we change the tempo
at any later instant?
6. For a format 1 file should eack track be played on a separate MIDI
channel? If so, what happens if the number of tracks exceeds 16? And
also what exactly is the difference between format 0 and 1 files if
the above statement is true? (The example given at the end of the
specification uses the same musical piece to produce either format 0
or 1 file but I didn't understand the difference as far as the output
of the synthesis is concerned)
7. For note on/off events how do we know whether it is a whole note or
a half note or a quarter note etc? Simply by checking the time during
which they are on? Can a whole note exceed the time for the note as
specified by the tempo?
Sorry for the rather long mail. Thanks a lot in advance!!
More information about the music-dsp