Crossfade

Overview

Crossfade between two signals a and b using some position pos (a value between 0 and 1). When the position is 0, it is signal A, when position is 1, it is signal B.

Tangled Files

crossfade.c and crossfade.h.

#ifndef SK_CROSSFADE_H
#define SK_CROSSFADE_H

#ifndef SKFLT
#define SKFLT float
#endif

<<funcdefs>>
#endif

#include <math.h>
#include "crossfade.h"

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

#define SQRT2 1.41421356237309504880

<<funcs>>

Linear Crossfade

A linear crossfade is simply linear interpolation.

This is done with sk_crossfade_linear.

SKFLT sk_crossfade_linear(SKFLT a, SKFLT b, SKFLT pos);

SKFLT sk_crossfade_linear(SKFLT a, SKFLT b, SKFLT pos)
{
    return (1 - pos)*a + pos*b;
}

Square Root Crossfade

crossfade using sqrt.

SKFLT sk_crossfade_sqrt(SKFLT a, SKFLT b, SKFLT pos);

SKFLT sk_crossfade_sqrt(SKFLT a, SKFLT b, SKFLT pos)
{
    return a * sqrt(pos) + b * sqrt(1 - pos);
}

Equal Power

Uses equal power to do crossfade.

SKFLT sk_crossfade_equal(SKFLT a, SKFLT b, SKFLT pos);

SKFLT sk_crossfade_equal(SKFLT a, SKFLT b, SKFLT pos)
{
    SKFLT c;
    SKFLT s;
    c = cos(M_PI * pos * 0.5);
    s = sin(M_PI * pos * 0.5);

    a *= SQRT2 * (c + s) * 0.5;
    b *= SQRT2 * (c - s) * 0.5;

    return a + b;
}