PD help

[Martin Naef]

On 15.11.2011 16:27, Marc Nostromo [M-.-n] wrote:
> I'm trying to do some basic stuff in Pd and it turns hairy. Right now
> I'm recieving a continuous signal that I restrict to 0 and 1's so my
> stream now looks like
>
> 00000111100010010011111100000000
>
> I would like to send a midi note on only when there's a change 0->1 &
> 1->0. Any idea on how to achieve that ?

It's been a while since I did this kind of thing in Max, but I remember 
I had a similar issue when I wanted to filter out excessive data.

My idea would go along those lines:

Use a comparison operator that outputs a bang when left value != right value

The bang triggers your midi
The same bang also triggers an update of the right value in the 
comparator (in a sort of feedback loop)

This works nicely because most operators only output when the left input 
has changed, not the right one (or the other way around...). Otherwise, 
a set X message usually works as well (it only sets the value, but 
doesn't trigger)

How to store the last value to update the comparator? Use a value object 
that receives your input data, but prefix the data message with a SET so 
the value object doesn't output whenever it changes. Trigger the value 
instead with the output of the comparator.

Does that help? It's hard to describe without having Max running in 
front of me...

Martin