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Python Midi Package: writing events non-chronologically

P: n/a
tim
Someone using Python Midi Package from
http://www.mxm.dk/products/public/ lately?

I want to do the following :
write some note events in a midi file
then after doing that, put some controllers at the beginning of the
midifile
(because I want to be able to make those dependant on what notes were
just written)

def midctrls():
global roffset, melchan, roffset, gmt, timedisplay, out_file, midi,
usednotes, n
midi.reset_time() #seems to do nothing
for cha in range(16):
if cha==1:
midi.abs_time=0 #seems to do nothing
midi._relative_time = 0 #seems to do nothing, but I can
imagine why
midi._absolute_time = 0 #seems to do nothing
midi.update_time(new_time=0, relative=0) #although I give
the variable relative=0 it seems to be relative ?
midi.continuous_controller(cha, 0, 122)
(snip)

With this code I want a controller number 0 with value 122 to be written
at the beginning of my midifile.
It is written at the end, how I move the writing position to the beginning?

thanks for any help!
Nov 24 '05 #1
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P: n/a
tim wrote:
Someone using Python Midi Package from
http://www.mxm.dk/products/public/ lately?

I want to do the following :
write some note events in a midi file
then after doing that, put some controllers at the beginning of the
midifile
(because I want to be able to make those dependant on what notes were
just written)

def midctrls():
global roffset, melchan, roffset, gmt, timedisplay, out_file, midi,
usednotes, n
midi.reset_time() #seems to do nothing
for cha in range(16):
if cha==1:
midi.abs_time=0 #seems to do nothing
midi._relative_time = 0 #seems to do nothing, but I can
imagine why
midi._absolute_time = 0 #seems to do nothing
midi.update_time(new_time=0, relative=0) #although I give
the variable relative=0 it seems to be relative ?
midi.continuous_controller(cha, 0, 122)
(snip)

With this code I want a controller number 0 with value 122 to be written
at the beginning of my midifile.
It is written at the end, how I move the writing position to the beginning?

You should make a wrapper around the library that handles the midi
events in a data structure.

When your musical structure is then is complete, you use the midi
library to write it to disk.

I have attached a simple example here.

--

hilsen/regards Max M, Denmark

http://www.mxm.dk/
IT's Mad Science

# event classes. Only used internally by notes2midi
class NoteOn:

def __init__(self, time=0, pitch=64, velocity=64):
self.time = time
self.pitch = pitch
self.velocity = velocity

def __str__(self):
r = []
a = r.append
a('NoteOn')
a('time %s' % self.time)
a('pitch %s' % self.pitch)
a('velocity %s' % self.velocity)
return '\n'.join(r)

def render(self, channel, mididevice):
"Writes the event to a midi stream"
mididevice.note_on(channel=channel, note=self.pitch, velocity=self.velocity)

class NoteOff:

def __init__(self, time=0, pitch=64, velocity=64):
self.time = time
self.pitch = pitch
self.velocity = velocity

def __str__(self):
r = []
a = r.append
a('NoteOff')
a('time %s' % self.time)
a('pitch %s' % self.pitch)
a('velocity %s' % self.velocity)
return '\n'.join(r)

def render(self, channel, mididevice):
"Writes the event to a midi stream"
mididevice.note_off(channel=channel, note=self.pitch, velocity=self.velocity)


def notes2midi(notes, midi):
"Turns a list of notes into a midi stream"
# notes have absolute time values!!!

# first turn notes into events (split into note-on / note-off)
events = []
for note in notes:
on_event = NoteOn(note.time, note.pitch, note.velocity)
events.append(on_event)
off_event = NoteOff(note.time+note.duration, note.pitch, note.velocity)
events.append(off_event)
# sort them in order of time
events.sort(lambda x,y: cmp(x.time, y.time))

# midi device writing
# non optional midi framework
midi.header()
midi.start_of_track()
midi.reset_time()
absolute_time = 0
for event in events:
delta_time = event.time - absolute_time
absolute_time = event.time
# write the data
midi.update_time(delta_time)
event.render(0, midi)
midi.end_of_track()
# non optional midi framework
midi.update_time(0)
midi.end_of_track()

midi.eof()
if __name__ == '__main__':

from Pattern import Note

# a short example using notes, with no limits to number of simultaneous voices
# creates a list of ascending notes
track = [
Note(time=24*i, pitch=64+i, velocity=127, duration=24)
for i in range(16)
]
##################
# write the notes to the file

from midi.MidiOutFile import MidiOutFile

out_file = 'note-test.mid'
midi = MidiOutFile(out_file)
notes2midi(track, midi)

Nov 24 '05 #2

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