Chris Stecker

A while back I asked whether anyone has a version of scope~ that accepts 

an external trigger. This is a basic feature of real-world scopes and 

really necessary if you want to see what's happening simultaneously in 

different signals. (I'm building demos for an undergrad acoustics 

course, so accurate visualization is important). The response was 

basically negative, so I assume there is no such object.

I've tried to work around the problem by extracting triggers manually 

and adding them as large transients to each signal. It's easy enough to 

extract triggers, generate impulses, and add them to the signals. The 

problem is that they can be seen in the waveform. So I'd like to extract 

a trigger and then inhibit the extraction of succeeding triggers for 

some "holdoff" period. I am having a lot of difficulty with this bit. In 

principle, I should be able to generate any signal of the requisite 

holdoff duration, trigger it by the first impulse, and use that to mask 

out (by comparison or multiplication) the nuisance triggers. However, as 

far as I can tell, the only objects that would let me make a one-shot 

holdoff signal are line~, adsr~, etc. and all of these are triggered at 

the event level (i.e. by bangs) rather than the signal level. That means 

that while we wait for the bang to be processed, 2-3 extra trigger 

I would really appreciate any help that anyone can give me, either with 

collecting the first of a series of triggers or with otherwise 

synchronizing a number of scope~ objects. For the record, I need this to 

run under the MSP Runtime (students use it), so I've been avoiding 

G. Christopher Stecker, Ph.D.        

Assistant Professor - Speech & Hearing Sciences

Univ. of Washington - 1417 N.E. 42nd St - Seattle WA 98105

A while back I asked whether anyone has a version of scope~ that accepts 
an external trigger. This is a basic feature of real-world scopes and 
really necessary if you want to see what's happening simultaneously in 
different signals. (I'm building demos for an undergrad acoustics 
course, so accurate visualization is important). The response was 
basically negative, so I assume there is no such object.

I've tried to work around the problem by extracting triggers manually 
and adding them as large transients to each signal. It's easy enough to 
extract triggers, generate impulses, and add them to the signals. The 
problem is that they can be seen in the waveform. So I'd like to extract 
a trigger and then inhibit the extraction of succeeding triggers for 
some "holdoff" period. I am having a lot of difficulty with this bit. In 
principle, I should be able to generate any signal of the requisite 
holdoff duration, trigger it by the first impulse, and use that to mask 
out (by comparison or multiplication) the nuisance triggers. However, as 
far as I can tell, the only objects that would let me make a one-shot 
holdoff signal are line~, adsr~, etc. and all of these are triggered at 
the event level (i.e. by bangs) rather than the signal level. That means 
that while we wait for the bang to be processed, 2-3 extra trigger 
pulses get through to the waveform.

I would really appreciate any help that anyone can give me, either with 
collecting the first of a series of triggers or with otherwise 
synchronizing a number of scope~ objects. For the record, I need this to 
run under the MSP Runtime (students use it), so I've been avoiding 
jitter, etc.

Assistant Professor - Speech & Hearing Sciences
Univ. of Washington - 1417 N.E. 42nd St - Seattle WA 98105

triggering-the-scope

After banging my head against this for longer than I'd like to admit, I 

think I've come up with an acceptable workaround.

I extract triggers from the positive zero crossings (or other suitable 

event) and then use spike~ to compute intervals between triggers. I set 

spike~'s refractory time (right inlet) to just longer than the duration 

my scope~ is set to display; this gives me intervals suitable for 

triggering the display cleanly. From these intervals I compute the 

frequency of a separate triggering waveform, which I synthesize with 

cycle~ or phasor~. Extracting triggers from this waveform (as before) 

and adding them as large-amplitude impulses to the original waveform 

does the trick. The triggering phase of the scope~d waveform is not 

fixed, but that's ok for my purposes. I was more concerned that the 

phase of the triggering waveform would drift relative to the visualized 

signals. It does, but not too much. It actually looks quite steady.

I'm still interested in hearing of any other solutions, but this is a 

After banging my head against this for longer than I'd like to admit, I 
think I've come up with an acceptable workaround.

I extract triggers from the positive zero crossings (or other suitable 
event) and then use spike~ to compute intervals between triggers. I set 
spike~'s refractory time (right inlet) to just longer than the duration 
my scope~ is set to display; this gives me intervals suitable for 
triggering the display cleanly. From these intervals I compute the 
frequency of a separate triggering waveform, which I synthesize with 
cycle~ or phasor~. Extracting triggers from this waveform (as before) 
and adding them as large-amplitude impulses to the original waveform 
does the trick. The triggering phase of the scope~d waveform is not 
fixed, but that's ok for my purposes. I was more concerned that the 
phase of the triggering waveform would drift relative to the visualized 
signals. It does, but not too much. It actually looks quite steady.

I'm still interested in hearing of any other solutions, but this is a 
pretty usable solution.

a different route would be to use the Ircam Gabor and FTM libs:

http://recherche.ircam.fr/equipes/temps-reel/ftm/index.html

You should be able to do something similar with the new audio to 

jitter objects that are part of Jitter 1.5.

You should be able to do something similar with the new audio to  
jitter objects that are part of Jitter 1.5.

Hi Chris - unless there's some kind of licensing restriction that I am

forgetting, there's no reason that you can use Jitter with Max/MSP

runtime. The jit.catch~ object will do exactly what you want.

Hi Chris - unless there's some kind of licensing restriction that I am
forgetting, there's no reason that you can use Jitter with Max/MSP
runtime.  The jit.catch~ object will do exactly what you want.

Triggering the scope~