Re: transform midi Control Change 7 into velocity events?

Philippe Hezaine <philippe.hezaine@xxxxxxx> · Fri, 21 Nov 2008 13:27:18 +0100

Dominic Sacré a écrit :
On Thursday 20 November 2008 23:49:46 Philippe Hezaine wrote:
I'm not sure mididings is the right tool for the job. The Python code
to transform the events would be quite simple, but mididings doesn't
support reading/writing MIDI files (yet?). You could of course use a
separate MIDI player/recorder, and route the events through mididings,
but you'd lose all meta information (tempo, time signature, etc.) from
the original file.
Yes. I was sucessfull to loop a midi file with Jack and Rosegarden. The
outputs was routed through mididings and went back to Rg for a new
record on a new track. But it was not for this purpose and i didn't look
for the meta information.
But for now, if i have a copy about these informations may be i can try
again this experience? It isn't a piece of music, only a succession of
drums patterns. I can organize them to avoid different time signature...

Recording to a new track in the same Rosegarden session is actually a very 
good idea, I didn't think of that... You wouldn't lose anything that way.

As for the transformation, something like this should do the trick (not 
thoroughly tested):

from mididings import *

class Volume2Velocity:
    def __init__(self):
        self.vol = {}
    def __call__(self, ev):
        if ev.type_ == CTRL and ev.param == 7:
            self.vol[ev.channel] = ev.value
            return None
        elif ev.type_ == NOTEON and ev.channel in self.vol:
            ev.velocity = self.vol[ev.channel]
        return ev

run(Call(Volume2Velocity()))

As far as I can see, all tracks in your MIDI file are on the same
channel, so CC #7 messages on one track will affect the other tracks as
well. You should probably assign a different channel to each track.
No. Like i have said these are drums patterns written by Lilypond. After
the famous transformation i could join all the tracks in one if i want.

Yes, but then you need to do the transformation one track at a time. If you 
play multiple tracks through the same MIDI port on the same channel, some 
notes will get the wrong velocity (unless every note event is immediately 
preceded by a volume change).

Cheers,

Dominic

Thanks too much for your time and your information.

Bingo! I think it's the first time we get from a Lilypond file a midi 
file with velocities values. But for all you're right. Note that I 
cannot get a clean file with a loop in the same Rosegarden's session. I 
have freezes and even crashes. Hence i output the midi from Rg through 
mididings -> recording in Muse.
The raw outcome is in attach.
1) You could see a little latency in the attacks.
2) I lose the Lilypond header
3) Strangely i can't open the new file with the drum editor in 
Rosegarden though it is on channel 10. (meta information?)

Anyway, thanks so much.

Have fun.
--
  Phil.
Superbonus-Project (Site principal) <http://superbonus.project.free.fr>

Superbonus-Project (Plate-forme d'échange):
<http://philippe.hezaine.free.fr>

Attachment:
Merengue-avec-velocite.mid

Description: Binary data
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