mirror of https://github.com/mpv-player/mpv
258 lines
6.9 KiB
C
258 lines
6.9 KiB
C
/*=============================================================================
|
|
//
|
|
// This software has been released under the terms of the GNU Public
|
|
// license. See http://www.gnu.org/copyleft/gpl.html for details.
|
|
//
|
|
// Copyright 2001 Anders Johansson ajh@atri.curtin.edu.au
|
|
//
|
|
//=============================================================================
|
|
*/
|
|
|
|
/* Design and implementation of different types of digital filters
|
|
|
|
*/
|
|
#include <math.h>
|
|
#include "dsp.h"
|
|
|
|
/* C implementation of FIR filter y=w*x
|
|
|
|
n number of filter taps, where mod(n,4)==0
|
|
w filter taps
|
|
x input signal must be a circular buffer which is indexed backwards
|
|
*/
|
|
inline _ftype_t fir(register unsigned int n, _ftype_t* w, _ftype_t* x)
|
|
{
|
|
register _ftype_t y; // Output
|
|
y = 0.0;
|
|
do{
|
|
n--;
|
|
y+=w[n]*x[n];
|
|
}while(n != 0);
|
|
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
|
|
*/
|
|
inline _ftype_t* 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 = fir(n,wt,xt);
|
|
wt+=n;
|
|
xt+=nt;
|
|
y+=s;
|
|
}
|
|
return y;
|
|
}
|
|
|
|
/* Add new data to circular queue designed to be used with a parallel
|
|
FIR filter, with d filters. xq is the circular queue, in pointing
|
|
at the new samples, xi current index in xq and n the length of the
|
|
filter. xq must be n*2 by k big, s is the index for in.
|
|
*/
|
|
inline int updatepq(unsigned int n, unsigned int d, unsigned int xi, _ftype_t** xq, _ftype_t* in, unsigned int s)
|
|
{
|
|
register _ftype_t* txq = *xq + xi;
|
|
register int nt = n*2;
|
|
|
|
while(d-- >0){
|
|
*txq= *(txq+n) = *in;
|
|
txq+=nt;
|
|
in+=s;
|
|
}
|
|
return (++xi)&(n-1);
|
|
}
|
|
|
|
|
|
/* 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
|
|
*/
|
|
int design_fir(unsigned int n, _ftype_t* w, _ftype_t* fc, unsigned int flags, _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 * M_PI; // 2*pi*fc1
|
|
_ftype_t k2 = 0.5 * (_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 = 0.0; // Gain
|
|
_ftype_t t1,t2,t3; // Temporary variables
|
|
_ftype_t fc1,fc2; // Cutoff frequencies
|
|
|
|
// Sanity check
|
|
if(!w || (n == 0)) return -1;
|
|
|
|
// Get window coefficients
|
|
switch(flags & WINDOW_MASK){
|
|
case(BOXCAR):
|
|
boxcar(n,w); break;
|
|
case(TRIANG):
|
|
triang(n,w); break;
|
|
case(HAMMING):
|
|
hamming(n,w); break;
|
|
case(HANNING):
|
|
hanning(n,w); break;
|
|
case(BLACKMAN):
|
|
blackman(n,w); break;
|
|
case(FLATTOP):
|
|
flattop(n,w); break;
|
|
case(KAISER):
|
|
kaiser(n,w,opt); break;
|
|
default:
|
|
return -1;
|
|
}
|
|
|
|
if(flags & (LP | HP)){
|
|
fc1=*fc;
|
|
// Cutoff frequency must be < 0.5 where 0.5 <=> Fs/2
|
|
fc1 = ((fc1 <= 1.0) && (fc1 > 0.0)) ? fc1/2 : 0.25;
|
|
k1 *= fc1;
|
|
|
|
if(flags & LP){ // 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] * 2.0;
|
|
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] = 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] = 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] = -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(flags & (BP | BS)){
|
|
fc1=fc[0];
|
|
fc2=fc[1];
|
|
// Cutoff frequencies must be < 1.0 where 1.0 <=> Fs/2
|
|
fc1 = ((fc1 <= 1.0) && (fc1 > 0.0)) ? fc1/2 : 0.25;
|
|
fc2 = ((fc2 <= 1.0) && (fc2 > 0.0)) ? fc2/2 : 0.25;
|
|
k3 = k1 * fc2; // 2*pi*fc2
|
|
k1 *= fc1; // 2*pi*fc1
|
|
|
|
if(flags & BP){ // Band pass
|
|
// Calculate center tap
|
|
if (o){
|
|
g=w[end]*(fc1+fc2);
|
|
w[end] = (fc2 - fc1) * w[end] * 2.0;
|
|
}
|
|
|
|
// Create filter
|
|
for (i=0 ; i<end ; i++){
|
|
t1 = (_ftype_t)(i+1) - k2;
|
|
t2 = sin(k3 * t1)/(M_PI * t1); // Sinc fc2
|
|
t3 = 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] = 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 = sin(k1 * t1)/(M_PI * t1); // Sinc fc1
|
|
t3 = 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 0;
|
|
}
|
|
|
|
/* Design polyphase FIR filter from prototype filter
|
|
|
|
n length of prototype filter
|
|
k number of polyphase components
|
|
w prototype filter taps
|
|
pw Parallel FIR filter
|
|
g Filter gain
|
|
flags FWD forward indexing
|
|
REW reverse indexing
|
|
ODD multiply every 2nd filter tap by -1 => HP filter
|
|
|
|
returns 0 if OK, -1 if fail
|
|
*/
|
|
int design_pfir(unsigned int n, unsigned int k, _ftype_t* w, _ftype_t** pw, _ftype_t g, unsigned int flags)
|
|
{
|
|
int l = (int)n/k; // Length of individual FIR filters
|
|
int i; // Counters
|
|
int j;
|
|
_ftype_t t; // g * w[i]
|
|
|
|
// Sanity check
|
|
if(l<1 || k<1 || !w || !pw)
|
|
return -1;
|
|
|
|
// Do the stuff
|
|
if(flags&REW){
|
|
for(j=l-1;j>-1;j--){//Columns
|
|
for(i=0;i<(int)k;i++){//Rows
|
|
t=g * *w++;
|
|
pw[i][j]=t * ((flags & ODD) ? ((j & 1) ? -1 : 1) : 1);
|
|
}
|
|
}
|
|
}
|
|
else{
|
|
for(j=0;j<l;j++){//Columns
|
|
for(i=0;i<(int)k;i++){//Rows
|
|
t=g * *w++;
|
|
pw[i][j]=t * ((flags & ODD) ? ((j & 1) ? 1 : -1) : 1);
|
|
}
|
|
}
|
|
}
|
|
return -1;
|
|
}
|