/**
* Calculate first order shelving filter. Filter is not directly usable by the
* filter_process() function.
* @param cutoff shelf midpoint frequency. See eq_pk_coefs for format.
* @param A decibel value multiplied by ten, describing gain/attenuation of
* shelf. Max value is 24 dB.
* @param low true for low-shelf filter, false for high-shelf filter.
* @param c pointer to coefficient storage. Coefficients are s4.27 format.
*/
void filter_shelf_coefs(unsigned long cutoff, long A, bool low, int32_t *c)
{
long sin, cos;
int32_t b0, b1, a0, a1; /* s3.28 */
const long g = get_replaygain_int(A*5) << 4; /* 10^(db/40), s3.28 */
sin = fp_sincos(cutoff/2, &cos);
if (low) {
const int32_t sin_div_g = fp_div(sin, g, 25);
const int32_t sin_g = FRACMUL(sin, g);
cos >>= 3;
b0 = sin_g + cos; /* 0.25 .. 4.10 */
b1 = sin_g - cos; /* -1 .. 3.98 */
a0 = sin_div_g + cos; /* 0.25 .. 4.10 */
a1 = sin_div_g - cos; /* -1 .. 3.98 */
} else {
static void init_tables(void)
{
int i;
int pfrac;
unsigned long phase;
long sin;
phase = pfrac = 0;
for (i = 0; i < TABLE_SIZE; i++) {
sin = fp_sincos(phase, NULL);
xtable[i] = RADIUS_X + sin / DIV_X;
ytable[i] = RADIUS_Y + sin / DIV_Y;
phase += PHASE_STEP;
pfrac += PHASE_FRAC;
if (pfrac >= TABLE_SIZE) {
pfrac -= TABLE_SIZE;
phase++;
}
}
}
static void init_clock(void)
{
int i;
int pfrac;
unsigned long phase;
long sin, cos;
phase = pfrac = 0;
for (i = 0; i < 60; i++) {
sin = fp_sincos(phase, &cos);
xminute[i] = LCD_WIDTH/2 + sin / DIV_MX;
yminute[i] = LCD_HEIGHT/2 - cos / DIV_MY;
xhour[i] = LCD_WIDTH/2 + sin / DIV_HX;
yhour[i] = LCD_HEIGHT/2 - cos / DIV_HY;
phase += CLOCK_STEP;
pfrac += CLOCK_FRAC;
if (pfrac >= 60) {
pfrac -= 60;
phase++;
}
}
}
