/****************************************************************
* Window the samples then,
* Fast Fourier transform of the input samples.
*
* ( call the FHT-based fft() in fft.c )
*
*
****************************************************************/
static void psycho_1_hann_fft_pickmax(FLOAT sample[FFT_SIZE], mask power[HAN_SIZE],
FLOAT spike[SBLIMIT], FLOAT energy[FFT_SIZE])
{
FLOAT x_real[FFT_SIZE];
register int i, j;
register FLOAT sqrt_8_over_3;
static int init = 0;
static FLOAT window[FFT_SIZE];
FLOAT sum;
if (!init) {
/* calculate window function for the Fourier transform */
/* These values need only be initiliased once, regardless of the caller */
sqrt_8_over_3 = pow(8.0 / 3.0, 0.5);
for (i = 0; i < FFT_SIZE; i++) {
/* Hann window formula */
window[i] = sqrt_8_over_3 * 0.5 * (1 - cos(2.0 * PI * i / (FFT_SIZE))) / FFT_SIZE;
}
init = 1;
}
for (i = 0; i < FFT_SIZE; i++)
x_real[i] = (FLOAT) (sample[i] * window[i]);
psycho_1_fft(x_real, energy, FFT_SIZE);
for (i = 0; i < HAN_SIZE; i++) { /* calculate power density spectrum */
if (energy[i] < 1E-20)
power[i].x = -200.0 + POWERNORM;
else
power[i].x = 10 * log10(energy[i]) + POWERNORM;
power[i].next = STOP;
power[i].type = FALSE;
}
/* Calculate the sum of spectral component in each subband from bound 4-16 */
#define CF 1073741824 /* pow(10, 0.1*POWERNORM) */
#define DBM 1E-20 /* pow(10.0, 0.1*DBMIN */
for (i = 0; i < HAN_SIZE; spike[i >> 4] = 10.0 * log10(sum), i += 16) {
for (j = 0, sum = DBM; j < 16; j++)
sum += CF * energy[i + j];
}
}
/* ISO11172 Sec D.1 Step 1 - Window with HANN and then perform the FFT */
static void psycho_3_fft(FLOAT sample[BLKSIZE], FLOAT energy[BLKSIZE])
{
FLOAT x_real[BLKSIZE];
int i;
static int init = 0;
static FLOAT window[FFT_SIZE];
if (!init) { /* calculate window function for the Fourier transform */
FLOAT sqrt_8_over_3 = pow(8.0 / 3.0, 0.5);
for (i = 0; i < BLKSIZE; i++) {
window[i] = sqrt_8_over_3 * 0.5 * (1 - cos(2.0 * PI * i / (BLKSIZE))) / BLKSIZE;
}
init++;
}
/* convolve the samples with the hann window */
for (i = 0; i < BLKSIZE; i++)
x_real[i] = (FLOAT) (sample[i] * window[i]);
/* do the FFT */
psycho_1_fft(x_real, energy, BLKSIZE);
}
