[music-dsp] Cascaded biquad filter structures

robert bristow-johnson rbj at audioimagination.com
Fri Oct 5 19:20:40 EDT 2007


"Luigi Castelli" <superbigio at yahoo.com> writes:
> 
> I am interested in processing 4 biquad structures in parallel.
> In a bank of biquads in parallel the vectorization gives about a 3x
> speed up compared to scalar code.
> 
> I am wondering if a similar optimization can be obtained even if the
> biquads are in series. What is discouraging to me is that in a cascaded
> structure you have to wait for the output of one biquad before being
> able to process the next,

not if you're willing to put up with some pipeline delay.  the output of the one biquad goes into a delay line at least as long as your vector length.  the input of the next biquad comes from the output of that delay line.  this delay line is actually two vectors and you ping-pong them at the process vector start time, swapping their roles between "output of one" and "input to next".  i think they call this "double buffering".  i dunno.

--

r b-j                  rbj at audioimagination.com

"Imagination is more important than knowledge."



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