saw.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "synth.h"
#include "rate.inc"

/* saw: generate a saw wave */

static float saw(float input, int up)
{
	double unused;
	input = modf(input, &unused); /* same as input = fmod(input, 1.0f) */
	return 2 * (input - 0.5f) * (up ? 1.0f : -1.0f);
}

int main(int argc, char *argv[])
{
	float freq = 1000, amp = 0.5f, phase = 0.0f;
	float period;
	long len;
	long n;
	int up = 1;
	int i;

	get_rate();
	len = RATE;

	/* read options */
	for (i = 1; i < argc; i++)
	{
		if (!strcmp(argv[i], "-freq") && i+1 < argc)
			freq = atof(argv[++i]); /* frequency of the wave */
		else if (!strcmp(argv[i], "-amp") && i+1 < argc)
			amp = atof(argv[++i]);  /* amplitude from 0 to 1 */
		else if (!strcmp(argv[i], "-len") && i+1 < argc)
			len = atof(argv[++i]) / 1000.0f * RATE; /* length in ms */
		else if (!strcmp(argv[i], "-phase") && i+1 < argc)
			phase = atof(argv[++i]); /* phase in degrees */
		else if (!strcmp(argv[i], "-down"))
			up = 0;
		else if (!strcmp(argv[i], "-help"))
		{
			fprintf(stderr, "options: -freq arg, -amp arg, -len "
				"arg, -phase arg, -down (default is up)\n");
			exit(0);
		}
	}

	/* check options */
	freq  = CLAMP(0.01f, freq, RATE / 22.0f * 10.f);
	amp   = CLAMP(0.0f, amp, 1.0f);
	phase = CLAMP(0.0f, phase, 359.99f);

	/* convert options */
	period = RATE / freq;
	phase /= 360.0f;

	phase += 0.5f; /* start at 0 */
	phase *= period;

	SET_BINARY_MODE
	for (n = 0; n < len; n++)
	{
		float f;

		f = saw((n + phase) / period, up) * amp;

		/* left channel */
		if (fwrite(&f, sizeof f, 1, stdout) < 1)
			break;

		/* right channel */
		if (fwrite(&f, sizeof f, 1, stdout) < 1)
			break;
	}

	return 0;
}