> On 04/27/2023 5:51 PM EDT Yisheng Jiang <[email protected]> wrote: > > > It took a couple days for your suggestion to sink it (possibly) > > > > > On Apr 25, 2023, at 9:19 PM, Ariadne Lewis-Towbes <[email protected]> wrote: > > > > You won't be able to fade between two filtered blocks of complex > > (non-sinusoidal) input to the same effect as modulating an arbitrary single > > filter's frequency. That said, when modulating an IIR filter such as a > > biquad (as shown in your second email's link), you should not need to > > compute the z-transform. You may simply modulate the biquad's parameters > > repeatedly, > > By this you mean compute biquad parameters for start and ending freq, then > incrementing the a0, a1 etc? >
Yisheng, if the biquad is not being modulated drasitically, then you might compute the coefficients once every block of samples and linearly interpolate and increment the coefficients on a sample-by-sample basis. And, instead of the standard Direct 1 or Direct 2 form, you should use either a lattice form or a normalized ladder form. https://urldefense.proofpoint.com/v2/url?u=https-3A__dsp.stackexchange.com_questions_42006_iir-2Dlattice-2Dfilter-2Din-2Dc-2Dprogramming_42008-2342008&d=DwICaQ&c=009klHSCxuh5AI1vNQzSO0KGjl4nbi2Q0M1QLJX9BeE&r=TRvFbpof3kTa2q5hdjI2hccynPix7hNL2n0I6DmlDy0&m=M3idWyNBI3vNjK8COAIGJ_rQGKnjjNj_dLsI0sXKfG9-1Qq4IcajLFjkWV0PJlxe&s=yMdj_g6b0rxu830QedRv4ENWciBAtSvfk73fZl8vuX0&e= https://urldefense.proofpoint.com/v2/url?u=https-3A__dsp.stackexchange.com_questions_48255_real-2Dtime-2Dmodulated-2Diir-2Dfilter_48299-2348299&d=DwICaQ&c=009klHSCxuh5AI1vNQzSO0KGjl4nbi2Q0M1QLJX9BeE&r=TRvFbpof3kTa2q5hdjI2hccynPix7hNL2n0I6DmlDy0&m=M3idWyNBI3vNjK8COAIGJ_rQGKnjjNj_dLsI0sXKfG9-1Qq4IcajLFjkWV0PJlxe&s=rWAtdXhlYvj2OyV2QHjc7TxomvVtwd_dtO_urUdw7Oc&e= This form makes one coefficient (k1) solely determine the resonant frequency of the biquad. -- r b-j . _ . _ . _ . _ [email protected] "Imagination is more important than knowledge." . . .
