// create spgram object
// _nfft : FFT size
// _wtype : window type, e.g. LIQUID_WINDOW_HAMMING
// _window_len : window length
// _delay : delay between transforms, _delay > 0
SPGRAM() SPGRAM(_create)(unsigned int _nfft,
int _wtype,
unsigned int _window_len,
unsigned int _delay)
{
// validate input
if (_nfft < 2) {
fprintf(stderr,"error: spgram%s_create(), fft size must be at least 2\n", EXTENSION);
exit(1);
} else if (_window_len > _nfft) {
fprintf(stderr,"error: spgram%s_create(), window size cannot exceed fft size\n", EXTENSION);
exit(1);
} else if (_window_len == 0) {
fprintf(stderr,"error: spgram%s_create(), window size must be greater than zero\n", EXTENSION);
exit(1);
} else if (_wtype == LIQUID_WINDOW_KBD && _window_len % 2) {
fprintf(stderr,"error: spgram%s_create(), KBD window length must be even\n", EXTENSION);
exit(1);
} else if (_delay == 0) {
fprintf(stderr,"error: spgram%s_create(), delay must be greater than 0\n", EXTENSION);
exit(1);
}
// allocate memory for main object
SPGRAM() q = (SPGRAM()) malloc(sizeof(struct SPGRAM(_s)));
// set input parameters
q->nfft = _nfft;
q->wtype = _wtype;
q->window_len = _window_len;
q->delay = _delay;
q->frequency = 0;
q->sample_rate= -1;
// set object for full accumulation
SPGRAM(_set_alpha)(q, -1.0f);
// create FFT arrays, object
q->buf_time = (TC*) malloc((q->nfft)*sizeof(TC));
q->buf_freq = (TC*) malloc((q->nfft)*sizeof(TC));
q->psd = (T *) malloc((q->nfft)*sizeof(T ));
q->fft = FFT_CREATE_PLAN(q->nfft, q->buf_time, q->buf_freq, FFT_DIR_FORWARD, FFT_METHOD);
// create buffer
q->buffer = WINDOW(_create)(q->window_len);
// create window
q->w = (T*) malloc((q->window_len)*sizeof(T));
unsigned int i;
unsigned int n = q->window_len;
float beta = 10.0f;
float zeta = 3.0f;
for (i=0; i<n; i++) {
switch (q->wtype) {
case LIQUID_WINDOW_HAMMING: q->w[i] = hamming(i,n); break;
case LIQUID_WINDOW_HANN: q->w[i] = hann(i,n); break;
case LIQUID_WINDOW_BLACKMANHARRIS: q->w[i] = blackmanharris(i,n); break;
case LIQUID_WINDOW_BLACKMANHARRIS7: q->w[i] = blackmanharris7(i,n); break;
case LIQUID_WINDOW_KAISER: q->w[i] = kaiser(i,n,beta,0); break;
case LIQUID_WINDOW_FLATTOP: q->w[i] = flattop(i,n); break;
case LIQUID_WINDOW_TRIANGULAR: q->w[i] = triangular(i,n,n); break;
case LIQUID_WINDOW_RCOSTAPER: q->w[i] = liquid_rcostaper_windowf(i,n/3,n); break;
case LIQUID_WINDOW_KBD: q->w[i] = liquid_kbd(i,n,zeta); break;
default:
fprintf(stderr,"error: spgram%s_create(), invalid window\n", EXTENSION);
exit(1);
}
}
// scale by window magnitude, FFT size
float g = 0.0f;
for (i=0; i<q->window_len; i++)
g += q->w[i] * q->w[i];
g = M_SQRT2 / ( sqrtf(g / q->window_len) * sqrtf((float)(q->nfft)) );
// scale window and copy
for (i=0; i<q->window_len; i++)
q->w[i] = g * q->w[i];
// reset the spgram object
q->num_samples_total = 0;
q->num_transforms_total = 0;
SPGRAM(_reset)(q);
// return new object
return q;
}
/* Design FIR filter using the Window method
n filter length must be odd for HP and BS filters
w buffer for the filter taps (must be n long)
fc cutoff frequencies (1 for LP and HP, 2 for BP and BS)
0 < fc < 1 where 1 <=> Fs/2
flags window and filter type as defined in filter.h
variables are ored together: i.e. LP|HAMMING will give a
low pass filter designed using a hamming window
opt beta constant used only when designing using kaiser windows
returns 0 if OK, -1 if fail
*/
TfirFilter::_ftype_t* TfirFilter::design_fir(unsigned int *n, _ftype_t* fc, int type, int window, _ftype_t opt)
{
unsigned int o = *n & 1; // Indicator for odd filter length
unsigned int end = ((*n + 1) >> 1) - o; // Loop end
unsigned int i; // Loop index
_ftype_t k1 = 2 * _ftype_t(M_PI); // 2*pi*fc1
_ftype_t k2 = 0.5f * (_ftype_t)(1 - o);// Constant used if the filter has even length
_ftype_t k3; // 2*pi*fc2 Constant used in BP and BS design
_ftype_t g = 0.0f; // Gain
_ftype_t t1,t2,t3; // Temporary variables
_ftype_t fc1,fc2; // Cutoff frequencies
// Sanity check
if(*n==0) return NULL;
fc[0]=limit(fc[0],_ftype_t(0.001),_ftype_t(1));
if (!o && (type==TfirSettings::BANDSTOP || type==TfirSettings::HIGHPASS))
(*n)++;
_ftype_t *w=(_ftype_t*)aligned_calloc(sizeof(_ftype_t),*n);
// Get window coefficients
switch(window){
case(TfirSettings::WINDOW_BOX):
boxcar(*n,w); break;
case(TfirSettings::WINDOW_TRIANGLE):
triang(*n,w); break;
case(TfirSettings::WINDOW_HAMMING):
hamming(*n,w); break;
case(TfirSettings::WINDOW_HANNING):
hanning(*n,w); break;
case(TfirSettings::WINDOW_BLACKMAN):
blackman(*n,w); break;
case(TfirSettings::WINDOW_FLATTOP):
flattop(*n,w); break;
case(TfirSettings::WINDOW_KAISER):
kaiser(*n,w,opt); break;
default:
{
delete []w;
return NULL;
}
}
if(type==TfirSettings::LOWPASS || type==TfirSettings::HIGHPASS){
fc1=*fc;
// Cutoff frequency must be < 0.5 where 0.5 <=> Fs/2
fc1 = ((fc1 <= 1.0) && (fc1 > 0.0)) ? fc1/2 : 0.25f;
k1 *= fc1;
if(type==TfirSettings::LOWPASS){ // Low pass filter
// If the filter length is odd, there is one point which is exactly
// in the middle. The value at this point is 2*fCutoff*sin(x)/x,
// where x is zero. To make sure nothing strange happens, we set this
// value separately.
if (o){
w[end] = fc1 * w[end] * 2.0f;
g=w[end];
}
// Create filter
for (i=0 ; i<end ; i++){
t1 = (_ftype_t)(i+1) - k2;
w[end-i-1] = w[*n-end+i] = _ftype_t(w[end-i-1] * sin(k1 * t1)/(M_PI * t1)); // Sinc
g += 2*w[end-i-1]; // Total gain in filter
}
}
else{ // High pass filter
//if (!o) // High pass filters must have odd length
// return -1;
w[end] = _ftype_t(1.0 - (fc1 * w[end] * 2.0));
g= w[end];
// Create filter
for (i=0 ; i<end ; i++){
t1 = (_ftype_t)(i+1);
w[end-i-1] = w[*n-end+i] = _ftype_t(-1 * w[end-i-1] * sin(k1 * t1)/(M_PI * t1)); // Sinc
g += ((i&1) ? (2*w[end-i-1]) : (-2*w[end-i-1])); // Total gain in filter
}
}
}
if(type==TfirSettings::BANDPASS || type==TfirSettings::BANDSTOP){
fc1=fc[0];
fc2=limit(fc[1],_ftype_t(0.001),_ftype_t(1));
// Cutoff frequencies must be < 1.0 where 1.0 <=> Fs/2
fc1 = ((fc1 <= 1.0) && (fc1 > 0.0)) ? fc1/2 : 0.25f;
fc2 = ((fc2 <= 1.0) && (fc2 > 0.0)) ? fc2/2 : 0.25f;
k3 = k1 * fc2; // 2*pi*fc2
k1 *= fc1; // 2*pi*fc1
if(type==TfirSettings::BANDPASS){ // Band pass
// Calculate center tap
if (o){
g=w[end]*(fc1+fc2);
w[end] = (fc2 - fc1) * w[end] * 2.0f;
}
// Create filter
for (i=0 ; i<end ; i++){
t1 = (_ftype_t)(i+1) - k2;
t2 = _ftype_t(sin(k3 * t1)/(M_PI * t1)); // Sinc fc2
t3 = _ftype_t(sin(k1 * t1)/(M_PI * t1)); // Sinc fc1
g += w[end-i-1] * (t3 + t2); // Total gain in filter
w[end-i-1] = w[*n-end+i] = w[end-i-1] * (t2 - t3);
}
}
else{ // Band stop
//if (!o) // Band stop filters must have odd length
// return -1;
w[end] = _ftype_t(1.0 - (fc2 - fc1) * w[end] * 2.0);
g= w[end];
// Create filter
for (i=0 ; i<end ; i++){
t1 = (_ftype_t)(i+1);
t2 = _ftype_t(sin(k1 * t1)/(M_PI * t1)); // Sinc fc1
t3 = _ftype_t(sin(k3 * t1)/(M_PI * t1)); // Sinc fc2
w[end-i-1] = w[*n-end+i] = w[end-i-1] * (t2 - t3);
g += 2*w[end-i-1]; // Total gain in filter
}
}
}
// Normalize gain
g=1/g;
for (i=0; i<*n; i++)
w[i] *= g;
return w;
}
