Please correct me if I'm wrong. A filter can be written in the form: N(z) H (z)= ------------ D(z) where N(z) = a_0 + a_1*z[-1] +...+ a_n*z[-n] // as many a_coeff as zeros + a0 D(z) = b_0 + b_1*z[-1] +...+ b_m*z[-m] // as many b_coeff as poles + b0 "a" "b" coefficients may be real or complex numbers. In Chuck, OneZero lets you place ONE zero anywhere along the x axis, thus "a" is forced to be real, and I guess it implicitly puts a pole at origin (0,0) in order to have a causal filter. You may use the OneZero::zero() or the ::b0() and ::b1() methods to specify the location of the zero along the x-axis. ( a_coeffs are named "b" in Chuck, and b_coeffs as "a", but that's just the name) OneZero::zero() can be regarded as the following expression: H(z) = 1 - radius*z[-1], thus a normalised filter i.e gain=1. OneZero::b0(), OneZero::b1() can be regarded as H(z) = b0 + b1*z[-1], equivlaent to H(z) = b0*(1 + b1/b0*z[-1] ), thus a filter with gain 1/b0 Something like this: /\ Im | | | | -----------------x-----------o---> Re | rad | <---------> | | hope this helps, eduard On Jul 28, 2006, at 4:43 PM, Atte André Jensen wrote:

Hi

Ok, I'm interested in getting some basic filtering going, first maybe just a simple low pass filter. So I received my copy of "Real Sound Synthesis". Section 3.9 suggests a low pass filter could be realized with a one-zero filter with "a" set between 0 and 1. Looking at http://chuck.cs.princeton.edu/doc/program/ugen_full.html#OneZero I don't see any "a", and where in the book can I read about b0 and b1.

Moreover I wasn't able to locate any example code using OneZero, so if someone could provide me with a (couple of) simple example(s), I'd really appreciate it...

-- peace, love & harmony Atte

http://www.atte.dk | quartet: http://www.anagrammer.dk http://www.atte.dk/gps | compositions: http://www.atte.dk/ compositions _______________________________________________ chuck-users mailing list chuck-users@lists.cs.princeton.edu https://lists.cs.princeton.edu/mailman/listinfo/chuck-users