/*
* Updates the fourier transform of a sample window of N samples.
* Uses a sample cache to update the frequencies.
*/
void sdft(uint8_t new_sample, complex *freq, complex *coefficients)
{
uint8_t old = get_old_sample();
insert_sample(new_sample);
int8_t delta = (int8_t)(new_sample - old);
for (uint8_t i=0; i<N; i++) {
freq[i] = mul(addi(freq[i], delta), coefficients[i]);
}
}
void process_signal( void)
{
char *buff = malloc( CF_nread * CF_chans * CF_bytes);
if( !buff) bailout( "not enough memory for input buffer");
while( 1)
{
int i, q;
double f;
q = read_soundcard( buff);
// Unpack the input buffer and scale to -1..+1 for further processing.
if( CF_bytes == 1)
{
unsigned char *dp = (unsigned char *) buff;
if( CF_chans == 1)
for( i=0; i<q; i++)
{
f = *dp++;
insert_sample( &left, (f - 127)/128);
maybe_do_fft();
}
else // CF_chans == 2
for( i=0; i<q; i++)
{
f = *dp++;
insert_sample( &left, (f - 127)/128);
f = *dp++;
insert_sample( &right, (f - 127)/128);
maybe_do_fft();
}
}
else
if( CF_bytes == 2)
{
short *dp = (short *) buff;
if( CF_chans == 1)
for( i=0; i<q; i++)
{
f = *dp++;
insert_sample( &left, f/32768);
maybe_do_fft();
}
else // CF_chans == 2
for( i=0; i<q; i++)
{
f = *dp++;
insert_sample( &left, f/32768);
f = *dp++;
insert_sample( &right, f/32768);
maybe_do_fft();
}
}
else
if( CF_bytes == 3)
{
char *dp = buff;
if( CF_chans == 1)
for( i=0; i<q; i++)
{
f = (* (int *) dp) & 0xffffff; dp += 3;
insert_sample( &left, f/8388608);
maybe_do_fft();
}
else // CF_chans == 2
for( i=0; i<q; i++)
{
f = (* (int *) dp) & 0xffffff; dp += 3;
insert_sample( &left, f/8388608);
f = (* (int *) dp) & 0xffffff; dp += 3;
insert_sample( &right, f/8388608);
maybe_do_fft();
}
}
else
if( CF_bytes == 4)
{
int *dp = (int *) buff;
if( CF_chans == 1)
for( i=0; i<q; i++)
{
f = *dp++;
insert_sample( &left, f/2147483648UL);
maybe_do_fft();
}
else // CF_chans == 2
for( i=0; i<q; i++)
{
f = *dp++;
insert_sample( &left, f/2147483648UL);
f = *dp++;
insert_sample( &right, f/2147483648UL);
maybe_do_fft();
}
}
}
}
