brendan mccloskey

as an exercise in auto-didactics I am using the following paper as a Max diversion, building simple and hybrid combs in gen~:

http://www.cs.washington.edu/education/courses/cse490s/11au/Readings/Digital_Sound_Generation_2.pdf

Quite accessible for the non-mathematician, but there is one symbol I don't grasp: next to the summing symbol of a plus inside a circle, there often appears a plus, a minus or both, with no clue (for me) as to what this means in practice (eg, p.41, see attached image).

Hi
as an exercise in auto-didactics I am using the following paper as a Max diversion, building simple and hybrid combs in gen~:

beat-frei-filter-algorithms-simplest-question

the actual filter equations may as well be written in Cantonese as far as I'm concerned

I already looked inside various relevant helpfiles and references with no results pertaining to these exact symbols; I'm not using native objects, as a learning exercise (gen~, filters and string modelling), I'm not seeking to reinvent the wheel or duplicate the effort of others.

Roman,
I already looked inside various relevant helpfiles and references with no results pertaining to these exact symbols; I'm not using native objects, as a learning exercise (gen~, filters and string modelling), I'm not seeking to reinvent the wheel or duplicate the effort of others.

on a wild guess, could that not be related with the phase of the signal that would be resulting from those operations ?

I had the same thought. It seems like if you invert one, you'd leave the other uninverted and vice versa. It looks kind of like a shorthand to save from drawing two separate diagrams.

I know for sure the '-' sign means to invert the signal.

Not totally sure what the '±' sign means but my guess is that the two branches at that point need to be inverted from each other, one positive, one negative.

The [-! 0] Gen operator works for inversion just like in Max.

I know for sure the '-' sign means to invert the signal. 

The [-! 0] Gen operator works for inversion just like in Max.


Thanks vichug auralacuity and stringtapper

There may well be "better" sources for DIY filter algorithms in Max-speak for the non-mathematician, and that this symbolic is rare or even erroneous, but phase inversion sounds convincing.

stringtapper also linked to some great shorthand and a massive resource pdf in this thread:

https://cycling74.com/forums/good-sources-for-gen-dsp-code-online/

stringtapper also linked to some great shorthand and a massive resource pdf in this thread:
https://cycling74.com/forums/good-sources-for-gen-dsp-code-online/


After looking back through my diagram packet that Wetterberg cited I think the '±' symbol definitely means to invert the line that feeds back.

If you find the 1st order allpass filter diagram in the PDF in Wetterberg's link you can see how it matches up with Frei's diagram, i.e. the all pass portion of the filter corresponds to the place where the symbols in question lie.

having a minus sign at one line going to the plus oderation simply renders it a subtraction, so it is the inversion of one signal. I have never seen the +- thing in this way but I would guess it means that there are two variations present. If you look at the transfer functions you also have the +- thingy there and at fig 51 you even have the two different equations graphed and called "sum type" and "difference type"

Yes, I think it would be better to go through stringtapper's resource first, before exploring Beat Frei's paper. I kinda put the cart before the horse there.

Beat Frei filter algorithms - simplest question