float TaudioFilterHeadphone2::conv(const int nx, const int nk, const float *sx, const float *sk,const int offset)
{
/* k = reminder of offset / nx */
int k = offset >= 0 ? offset % nx : nx + (offset % nx);
if(nk + k <= nx) {
return af_filter_fir(nk, sx + k, sk);
} else {
return af_filter_fir(nk + k - nx, sx, sk + nx - k) + af_filter_fir(nx - k, sx + k, sk);
}
}
/* Convolution on a ring buffer
* nx: length of the ring buffer
* nk: length of the convolution kernel
* sx: ring buffer
* sk: convolution kernel
* offset: offset on the ring buffer, can be
*/
static float conv(const int nx, const int nk, const float *sx, const float *sk,
const int offset)
{
/* k = reminder of offset / nx */
int k = offset >= 0 ? offset % nx : nx + (offset % nx);
if(nk + k <= nx)
return af_filter_fir(nk, sx + k, sk);
else
return af_filter_fir(nk + k - nx, sx, sk + nx - k) +
af_filter_fir(nx - k, sx + k, sk);
}
/* C implementation of parallel FIR filter y(k)=w(k) * x(k) (where * denotes convolution)
n number of filter taps, where mod(n,4)==0
d number of filters
xi current index in xq
w filter taps k by n big
x input signal must be a circular buffers which are indexed backwards
y output buffer
s output buffer stride
*/
inline _ftype_t* af_filter_pfir(unsigned int n, unsigned int d, unsigned int xi, _ftype_t** w, _ftype_t** x, _ftype_t* y, unsigned int s)
{
register _ftype_t* xt = *x + xi;
register _ftype_t* wt = *w;
register int nt = 2*n;
while(d-- > 0){
*y = af_filter_fir(n,wt,xt);
wt+=n;
xt+=nt;
y+=s;
}
return y;
}
/* C implementation of parallel FIR filter y(k)=w(k) * x(k) (where * denotes convolution)
n number of filter taps, where mod(n,4)==0
d number of filters
xi current index in xq
w filter taps k by n big
x input signal must be a circular buffers which are indexed backwards
y output buffer
s output buffer stride
*/
FLOAT_TYPE* af_filter_pfir(unsigned int n, unsigned int d, unsigned int xi,
const FLOAT_TYPE** w, const FLOAT_TYPE** x, FLOAT_TYPE* y,
unsigned int s) {
register const FLOAT_TYPE* xt = *x + xi;
register const FLOAT_TYPE* wt = *w;
register int nt = 2*n;
while(d-- > 0) {
*y = af_filter_fir(n,wt,xt);
wt+=n;
xt+=nt;
y+=s;
}
return y;
}
