# Generator¶

• Author or source: Paul Sernine
• Type: antialiased sawtooth
• Created: 2006-02-23 22:38:56
notes
```This code generates a swept antialiasing sawtooth in a raw 16bit pcm file.
It is based on the quad differentiation of a 5th order polynomial. The polynomial
harmonics (and aliased harmonics) decay at 5*6 dB per oct. The differenciators correct the
spectrum and waveform, while aliased harmonics are still attenuated.
```
code
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47``` ```/* clair.c Examen Partiel 2b T.Rochebois 02/03/98 */ #include #include main() { double phase=0,dphase,freq,compensation; double aw0=0,aw1=0,ax0=0,ax1=0,ay0=0,ay1=0,az0=0,az1=0,sortie; short aout; int sr=44100; //sample rate (Hz) double f_debut=55.0;//start freq (Hz) double f_fin=sr/6.0;//end freq (Hz) double octaves=log(f_fin/f_debut)/log(2.0); double duree=50.0; //duration (s) int i; FILE* f; f=fopen("saw.pcm","wb"); for(i=0;i1.0) phase-=2.0; //phase wrapping (-1,+1) //polynomial calculation (extensive continuity at -1 +1) // 7 1 3 1 5 //P(x) = --- x - -- x + --- x // 360 36 120 aw0=phase*(7.0/360.0 + phase*phase*(-1/36.0 + phase*phase*(1/120.0))); // quad differentiation (first order high pass filters) ax0=aw1-aw0; ay0=ax1-ax0; az0=ay1-ay0; sortie=az1-az0; //compensation of the attenuation of the quad differentiator //this can be calculated at "control rate" and linearly //interpolated at sample rate. compensation=1.0/(dphase*dphase*dphase*dphase); // compensation and output aout=(short)(15000.0*compensation*sortie); fwrite(&aout,1,2,f); //old memories of differentiators aw1=aw0; ax1=ax0; ay1=ay0; az1=az0; } fclose(f); } ```

```More infos and discussions in the KVR thread:
```nice but i prefer the fishy algo, it generates less alias.