aubio_filter_t * new_aubio_filter_biquad(lsmp_t b0, lsmp_t b1, lsmp_t b2, lsmp_t a1, lsmp_t a2)
create biquad filter with b0, b1, b2, a1, a2 coeffs
uint_t aubio_filter_set_biquad(aubio_filter_t *f, lsmp_t b0, lsmp_t b1, lsmp_t b2, lsmp_t a1, lsmp_t a2)
set coefficients of a biquad filter