Cheap pseudo-sinusoidal lfo

• Author or source: moc.regnimmu@regnimmuf
• Created: 2004-04-07 09:39:28

notes

Although the code is written in standard C++, this algorithm is really better suited for
dsps where one can take advantage of multiply-accumulate instructions and where the
required phase accumulator can be easily implemented by masking a counter.

It provides a pretty cheap roughly sinusoidal waveform that is good enough for an lfo.

code

// x should be between -1.0 and 1.0
inline
double pseudo_sine(double x)
{
    // Compute 2*(x^2-1.0)^2-1.0
    x *= x;
    x -= 1.0;
    x *= x;
    // The following lines modify the range to lie between -1.0 and 1.0.
   // If a range of between 0.0 and 1.0 is acceptable or preferable
   // (as in a modulated delay line) then you can save some cycles.
    x *= 2.0;
    x -= 1.0;
}

Comments

• Date: 2004-03-31 09:08:57
• By: ed.bew@hakkeb

You forgot a

return x;

• Date: 2004-04-05 19:43:15
• By: moc.regnimmu@regnimmuf

Doh! You're right.

-Frederick