mirror of
https://github.com/mpv-player/mpv
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1f6c494641
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@7569 b3059339-0415-0410-9bf9-f77b7e298cf2
258 lines
6.9 KiB
C
258 lines
6.9 KiB
C
/*=============================================================================
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//
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// This software has been released under the terms of the GNU Public
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// license. See http://www.gnu.org/copyleft/gpl.html for details.
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//
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// Copyright 2001 Anders Johansson ajh@atri.curtin.edu.au
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//
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//=============================================================================
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*/
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/* Design and implementation of different types of digital filters
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*/
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#include <math.h>
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#include "dsp.h"
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/* C implementation of FIR filter y=w*x
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n number of filter taps, where mod(n,4)==0
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w filter taps
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x input signal must be a circular buffer which is indexed backwards
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*/
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inline _ftype_t fir(register unsigned int n, _ftype_t* w, _ftype_t* x)
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{
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register _ftype_t y; // Output
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y = 0.0;
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do{
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n--;
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y+=w[n]*x[n];
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}while(n != 0);
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return y;
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}
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/* C implementation of parallel FIR filter y(k)=w(k) * x(k) (where * denotes convolution)
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n number of filter taps, where mod(n,4)==0
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d number of filters
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xi current index in xq
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w filter taps k by n big
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x input signal must be a circular buffers which are indexed backwards
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y output buffer
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s output buffer stride
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*/
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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)
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{
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register _ftype_t* xt = *x + xi;
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register _ftype_t* wt = *w;
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register int nt = 2*n;
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while(d-- > 0){
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*y = fir(n,wt,xt);
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wt+=n;
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xt+=nt;
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y+=s;
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}
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return y;
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}
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/* Add new data to circular queue designed to be used with a parallel
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FIR filter, with d filters. xq is the circular queue, in pointing
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at the new samples, xi current index in xq and n the length of the
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filter. xq must be n*2 by k big, s is the index for in.
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*/
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inline int updatepq(unsigned int n, unsigned int d, unsigned int xi, _ftype_t** xq, _ftype_t* in, unsigned int s)
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{
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register _ftype_t* txq = *xq + xi;
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register int nt = n*2;
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while(d-- >0){
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*txq= *(txq+n) = *in;
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txq+=nt;
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in+=s;
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}
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return (++xi)&(n-1);
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}
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/* Design FIR filter using the Window method
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n filter length must be odd for HP and BS filters
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w buffer for the filter taps (must be n long)
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fc cutoff frequencies (1 for LP and HP, 2 for BP and BS)
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0 < fc < 1 where 1 <=> Fs/2
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flags window and filter type as defined in filter.h
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variables are ored together: i.e. LP|HAMMING will give a
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low pass filter designed using a hamming window
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opt beta constant used only when designing using kaiser windows
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returns 0 if OK, -1 if fail
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*/
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int design_fir(unsigned int n, _ftype_t* w, _ftype_t* fc, unsigned int flags, _ftype_t opt)
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{
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unsigned int o = n & 1; // Indicator for odd filter length
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unsigned int end = ((n + 1) >> 1) - o; // Loop end
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unsigned int i; // Loop index
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_ftype_t k1 = 2 * M_PI; // 2*pi*fc1
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_ftype_t k2 = 0.5 * (_ftype_t)(1 - o);// Constant used if the filter has even length
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_ftype_t k3; // 2*pi*fc2 Constant used in BP and BS design
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_ftype_t g = 0.0; // Gain
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_ftype_t t1,t2,t3; // Temporary variables
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_ftype_t fc1,fc2; // Cutoff frequencies
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// Sanity check
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if(!w || (n == 0)) return -1;
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// Get window coefficients
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switch(flags & WINDOW_MASK){
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case(BOXCAR):
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boxcar(n,w); break;
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case(TRIANG):
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triang(n,w); break;
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case(HAMMING):
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hamming(n,w); break;
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case(HANNING):
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hanning(n,w); break;
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case(BLACKMAN):
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blackman(n,w); break;
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case(FLATTOP):
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flattop(n,w); break;
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case(KAISER):
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kaiser(n,w,opt); break;
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default:
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return -1;
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}
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if(flags & (LP | HP)){
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fc1=*fc;
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// Cutoff frequency must be < 0.5 where 0.5 <=> Fs/2
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fc1 = ((fc1 <= 1.0) && (fc1 > 0.0)) ? fc1/2 : 0.25;
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k1 *= fc1;
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if(flags & LP){ // Low pass filter
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// If the filter length is odd, there is one point which is exactly
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// in the middle. The value at this point is 2*fCutoff*sin(x)/x,
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// where x is zero. To make sure nothing strange happens, we set this
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// value separately.
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if (o){
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w[end] = fc1 * w[end] * 2.0;
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g=w[end];
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}
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// Create filter
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for (i=0 ; i<end ; i++){
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t1 = (_ftype_t)(i+1) - k2;
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w[end-i-1] = w[n-end+i] = w[end-i-1] * sin(k1 * t1)/(M_PI * t1); // Sinc
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g += 2*w[end-i-1]; // Total gain in filter
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}
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}
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else{ // High pass filter
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if (!o) // High pass filters must have odd length
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return -1;
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w[end] = 1.0 - (fc1 * w[end] * 2.0);
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g= w[end];
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// Create filter
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for (i=0 ; i<end ; i++){
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t1 = (_ftype_t)(i+1);
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w[end-i-1] = w[n-end+i] = -1 * w[end-i-1] * sin(k1 * t1)/(M_PI * t1); // Sinc
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g += ((i&1) ? (2*w[end-i-1]) : (-2*w[end-i-1])); // Total gain in filter
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}
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}
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}
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if(flags & (BP | BS)){
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fc1=fc[0];
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fc2=fc[1];
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// Cutoff frequencies must be < 1.0 where 1.0 <=> Fs/2
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fc1 = ((fc1 <= 1.0) && (fc1 > 0.0)) ? fc1/2 : 0.25;
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fc2 = ((fc2 <= 1.0) && (fc2 > 0.0)) ? fc2/2 : 0.25;
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k3 = k1 * fc2; // 2*pi*fc2
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k1 *= fc1; // 2*pi*fc1
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if(flags & BP){ // Band pass
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// Calculate center tap
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if (o){
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g=w[end]*(fc1+fc2);
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w[end] = (fc2 - fc1) * w[end] * 2.0;
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}
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// Create filter
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for (i=0 ; i<end ; i++){
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t1 = (_ftype_t)(i+1) - k2;
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t2 = sin(k3 * t1)/(M_PI * t1); // Sinc fc2
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t3 = sin(k1 * t1)/(M_PI * t1); // Sinc fc1
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g += w[end-i-1] * (t3 + t2); // Total gain in filter
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w[end-i-1] = w[n-end+i] = w[end-i-1] * (t2 - t3);
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}
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}
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else{ // Band stop
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if (!o) // Band stop filters must have odd length
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return -1;
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w[end] = 1.0 - (fc2 - fc1) * w[end] * 2.0;
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g= w[end];
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// Create filter
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for (i=0 ; i<end ; i++){
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t1 = (_ftype_t)(i+1);
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t2 = sin(k1 * t1)/(M_PI * t1); // Sinc fc1
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t3 = sin(k3 * t1)/(M_PI * t1); // Sinc fc2
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w[end-i-1] = w[n-end+i] = w[end-i-1] * (t2 - t3);
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g += 2*w[end-i-1]; // Total gain in filter
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}
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}
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}
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// Normalize gain
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g=1/g;
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for (i=0; i<n; i++)
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w[i] *= g;
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return 0;
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}
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/* Design polyphase FIR filter from prototype filter
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n length of prototype filter
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k number of polyphase components
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w prototype filter taps
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pw Parallel FIR filter
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g Filter gain
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flags FWD forward indexing
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REW reverse indexing
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ODD multiply every 2nd filter tap by -1 => HP filter
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returns 0 if OK, -1 if fail
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*/
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int design_pfir(unsigned int n, unsigned int k, _ftype_t* w, _ftype_t** pw, _ftype_t g, unsigned int flags)
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{
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int l = (int)n/k; // Length of individual FIR filters
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int i; // Counters
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int j;
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_ftype_t t; // g * w[i]
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// Sanity check
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if(l<1 || k<1 || !w || !pw)
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return -1;
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// Do the stuff
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if(flags&REW){
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for(j=l-1;j>-1;j--){//Columns
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for(i=0;i<(int)k;i++){//Rows
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t=g * *w++;
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pw[i][j]=t * ((flags & ODD) ? ((j & 1) ? -1 : 1) : 1);
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}
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}
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}
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else{
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for(j=0;j<l;j++){//Columns
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for(i=0;i<(int)k;i++){//Rows
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t=g * *w++;
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pw[i][j]=t * ((flags & ODD) ? ((j & 1) ? 1 : -1) : 1);
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}
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}
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}
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return -1;
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}
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