Dear all,

enclosed is an external I am working on to find the Average Magnitude Difference Function. It crashes PD at the moment, and I don't know why. I'm sure there must be a way to do this more efficiently - is my understanding of vectors right? and is it possible to compare two vectors in the signal block by input[i] > input[i+p] where *input is a pointer to a signal vector?

Best, Ed

Dr Edward Kelly Research Assistant in Sonic Arts London College of Communication University of the Arts London

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#include "m_pd.h"

static t_class *amdf_tilde_class;

typedef struct _amdf_tilde { t_object x_obj; t_sample input; t_sample f; t_outlet *x_outlet; t_float x_pitch; } t_amdf_tilde;

t_int *amdf_tilde_perform(t_int *w, t_amdf_tilde *x) { t_amdf_tilde *x = (t_amdf_tilde *) (w[1]); t_sample *input = (t_sample *) (w[2]); t_sample *errpr1 = (t_sample *) (w[3]); t_sample *errprx = (t_sample *) (w[4]); int n = (int) (w[5]); x->x_pitch = 0; // float sr = float sys_getsr(void); //how to get sample rate in external? int win = 674; int ti = 0; int sign = 1; int period = 40; *errpr1 = *errprx = 0;

while (n--) { for (ti=0;ti<=(win/2);ti++) { sign = (input[ti]-input[ti+1]) > 0 ? 1 : -1; *errpr1 += (input[ti]-input[ti+1])*sign; for (period=40;period>=(win/2);period++) for (ti=1; ti<=(win/2); ti++) { sign = (input[ti]-(input[ti+period])) > 0 ? 1 : -1; *errprx += (input[ti]-(input[ti+period]))*sign; x->x_pitch = (*errprx < *errpr1) ? 44100/(period+(*errprx / *errpr1)) : 0; } } *errpr1++; *errprx++; } return (w+6); outlet_float(&x->x_outlet, x->x_pitch); }

void amdf_tilde_dsp(t_amdf_tilde *x, t_signal **sp) { dsp_add(amdf_tilde_perform, 5, x, sp[0]->s_vec, sp[3]->s_vec, sp[2]->s_vec, sp[0]->s_n); }

void *amdf_tilde_new(t_floatarg f) { t_amdf_tilde *x = (t_amdf_tilde *)pd_new(amdf_tilde_class);

outlet_new(&x->x_obj, &s_signal); outlet_new(&x->x_obj, &s_signal); outlet_new(&x->x_obj, &s_float);

return (void *)x; }

void amdf_tilde_setup(void) { amdf_tilde_class = class_new(gensym("amdf~"), (t_newmethod)amdf_tilde_new, 0, sizeof(t_amdf_tilde), CLASS_DEFAULT, A_DEFFLOAT, 0);
class_addmethod(amdf_tilde_class, (t_method)amdf_tilde_dsp, gensym("dsp"), 0); CLASS_MAINSIGNALIN(amdf_tilde_class, t_amdf_tilde, f); }