As the description says, xoverT is a templated C++ class that implements a multiband crossover utilizing SVF filters (see below) and up to 4 bands are supported. Because it is templated C++ class it supports SIMD intrinsict vector construct.

For information on SVF (state variable filters) go to this site: http://www.cytomic.com/files/dsp/SvfLinearTrapOptimised2.pdf

This is a sophisticated and better sounding algorithm than the common nested LP/HP filters... and now how to use it:

// for iOS and OS X include simd for simd_double8, ..4, ..2 vectors
// already defined and many math functions provided via simd::sinf(some_simd_vector)
// for example. If you're going to use simd_double8 vectors, make sure to change 
// xover.h defines to reflect that... left as excercise for the user :)

#include <simd/simd.h>

// 4 = number of bands (got moved from Init into template parameter
// There is no longer need to call Init, and has been simply removed into
// the constructor, and the N of bands is now a template parameter for easy use

xoverT<double8,44100,4> cross;

in the further init or reset:

// setup the bands 1-85, 85-700, 700-3k, 3k-22kHz

// NOTE: indexing into bands has been changed from 0..N-1 
// to 1..N. So for 4-band crossover, you have 3 split points.
// Also: you do not need to make upper band split point it is done
// for you and set to a niquist frequency, that is samplerate/2
// Call this only once in the app per instantiation of xoverT or
// if or when the crossover frequency changes, but it will call reset
// and it will zero out the processed frame, just be aware of that

cross.set_freq( 1, 85 );
cross.set_freq( 2, 700 );
cross.set_freq( 3, 3000 );

// NOTE: you don't need to call cross.reset() it is called after each
// set_freq() call. But you can anyway, it won't hurt it

cross.reset();

your sample iteration loop would look like this:

// make sure to set those up with PCM data of course (in this case would be -1..1 perhaps,
// although vertically it doesn't matter it could be -32768.0 to 32767.0. Horizontally you have
// 44kHz as specified as a template parameter 44100. In oversample mode, you don't need to 
// multiply frequency in the set_freq() by oversample factor, only the sampling rate.

double8 in[1024], out[1024]; 

for (int k=0; k<1024; k++) 
{
    // set outLR to 0 each iteration because it contains sum of the total of bands samples
     
     double8 outLR = 0.0;

    // C++ is nifty isn't it? if you're using simd_doubleX vectors you can initialize
    // them with a constant like this and it will assign that constant to each of the double's
    // within that vector of 8 in this case
    
    cross.process( in[k] );

    for (int i=0; i < bands; i++)
    {
        double8 LR = cross.get_output( i + 1 );

        // .. do some  fancy dsp processing here to LR
    
        outLR += LR;     
    }

    // write into output buffer
    
    out[k] = outLR;
}

that's it!

DMT [email protected]