mirror of https://github.com/mpv-player/mpv
274 lines
8.0 KiB
C
274 lines
8.0 KiB
C
/*
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This is an libaf filter to do simple decoding of matrixed surround
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sound. This will provide a (basic) surround-sound effect from
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audio encoded for Dolby Surround, Pro Logic etc.
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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Original author: Steve Davies <steve@daviesfam.org>
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*/
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/* The principle: Make rear channels by extracting anti-phase data
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from the front channels, delay by 20ms and feed to rear in anti-phase
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*/
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/* SPLITREAR: Define to decode two distinct rear channels - this
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doesn't work so well in practice because separation in a passive
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matrix is not high. C (dialogue) to Ls and Rs 14dB or so - so
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dialogue leaks to the rear. Still - give it a try and send
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feedback. Comment this define for old behavior of a single
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surround sent to rear in anti-phase */
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#define SPLITREAR 1
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "af.h"
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#include "dsp.h"
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#define L 32 // Length of fir filter
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#define LD 65536 // Length of delay buffer
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// 32 Tap fir filter loop unrolled
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#define FIR(x,w,y) \
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y = ( w[0] *x[0] +w[1] *x[1] +w[2] *x[2] +w[3] *x[3] \
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+ w[4] *x[4] +w[5] *x[5] +w[6] *x[6] +w[7] *x[7] \
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+ w[8] *x[8] +w[9] *x[9] +w[10]*x[10]+w[11]*x[11] \
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+ w[12]*x[12]+w[13]*x[13]+w[14]*x[14]+w[15]*x[15] \
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+ w[16]*x[16]+w[17]*x[17]+w[18]*x[18]+w[19]*x[19] \
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+ w[20]*x[20]+w[21]*x[21]+w[22]*x[22]+w[23]*x[23] \
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+ w[24]*x[24]+w[25]*x[25]+w[26]*x[26]+w[27]*x[27] \
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+ w[28]*x[28]+w[29]*x[29]+w[30]*x[30]+w[31]*x[31])
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// Add to circular queue macro + update index
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#ifdef SPLITREAR
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#define ADDQUE(qi,rq,lq,r,l)\
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lq[qi]=lq[qi+L]=(l);\
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rq[qi]=rq[qi+L]=(r);\
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qi=(qi-1)&(L-1);
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#else
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#define ADDQUE(qi,lq,l)\
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lq[qi]=lq[qi+L]=(l);\
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qi=(qi-1)&(L-1);
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#endif
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// Macro for updating queue index in delay queues
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#define UPDATEQI(qi) qi=(qi+1)&(LD-1)
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// instance data
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typedef struct af_surround_s
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{
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float lq[2*L]; // Circular queue for filtering left rear channel
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float rq[2*L]; // Circular queue for filtering right rear channel
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float w[L]; // FIR filter coefficients for surround sound 7kHz low-pass
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float* dr; // Delay queue right rear channel
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float* dl; // Delay queue left rear channel
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float d; // Delay time
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int i; // Position in circular buffer
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int wi; // Write index for delay queue
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int ri; // Read index for delay queue
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}af_surround_t;
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// Initialization and runtime control
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static int control(struct af_instance_s* af, int cmd, void* arg)
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{
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af_surround_t *s = af->setup;
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switch(cmd){
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case AF_CONTROL_REINIT:{
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float fc;
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af->data->rate = ((af_data_t*)arg)->rate;
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af->data->nch = ((af_data_t*)arg)->nch*2;
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af->data->format = AF_FORMAT_FLOAT_NE;
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af->data->bps = 4;
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if (af->data->nch != 4){
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af_msg(AF_MSG_ERROR,"[surround] Only stereo input is supported.\n");
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return AF_DETACH;
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}
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// Surround filer coefficients
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fc = 2.0 * 7000.0/(float)af->data->rate;
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if (-1 == af_filter_design_fir(L, s->w, &fc, LP|HAMMING, 0)){
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af_msg(AF_MSG_ERROR,"[surround] Unable to design low-pass filter.\n");
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return AF_ERROR;
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}
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// Free previous delay queues
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if(s->dl)
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free(s->dl);
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if(s->dr)
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free(s->dr);
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// Allocate new delay queues
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s->dl = calloc(LD,af->data->bps);
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s->dr = calloc(LD,af->data->bps);
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if((NULL == s->dl) || (NULL == s->dr))
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af_msg(AF_MSG_FATAL,"[delay] Out of memory\n");
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// Initialize delay queue index
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if(AF_OK != af_from_ms(1, &s->d, &s->wi, af->data->rate, 0.0, 1000.0))
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return AF_ERROR;
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// printf("%i\n",s->wi);
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s->ri = 0;
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if((af->data->format != ((af_data_t*)arg)->format) ||
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(af->data->bps != ((af_data_t*)arg)->bps)){
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((af_data_t*)arg)->format = af->data->format;
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((af_data_t*)arg)->bps = af->data->bps;
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return AF_FALSE;
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}
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return AF_OK;
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}
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case AF_CONTROL_COMMAND_LINE:{
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float d = 0;
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sscanf((char*)arg,"%f",&d);
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if ((d < 0) || (d > 1000)){
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af_msg(AF_MSG_ERROR,"[surround] Invalid delay time, valid time values"
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" are 0ms to 1000ms current value is %0.3f ms\n",d);
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return AF_ERROR;
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}
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s->d = d;
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return AF_OK;
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}
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}
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return AF_UNKNOWN;
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}
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// Deallocate memory
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static void uninit(struct af_instance_s* af)
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{
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if(af->data)
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free(af->data->audio);
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free(af->data);
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free(af->setup);
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}
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// The beginnings of an active matrix...
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static float steering_matrix[][12] = {
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// LL RL LR RR LS RS
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// LLs RLs LRs RRs LC RC
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{.707, .0, .0, .707, .5, -.5,
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.5878, -.3928, .3928, -.5878, .5, .5},
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};
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// Experimental moving average dominance
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//static int amp_L = 0, amp_R = 0, amp_C = 0, amp_S = 0;
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// Filter data through filter
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static af_data_t* play(struct af_instance_s* af, af_data_t* data){
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af_surround_t* s = (af_surround_t*)af->setup;
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float* m = steering_matrix[0];
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float* in = data->audio; // Input audio data
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float* out = NULL; // Output audio data
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float* end = in + data->len / sizeof(float); // Loop end
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int i = s->i; // Filter queue index
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int ri = s->ri; // Read index for delay queue
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int wi = s->wi; // Write index for delay queue
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if (AF_OK != RESIZE_LOCAL_BUFFER(af, data))
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return NULL;
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out = af->data->audio;
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while(in < end){
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/* Dominance:
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abs(in[0]) abs(in[1]);
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abs(in[0]+in[1]) abs(in[0]-in[1]);
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10 * log( abs(in[0]) / (abs(in[1])|1) );
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10 * log( abs(in[0]+in[1]) / (abs(in[0]-in[1])|1) ); */
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/* About volume balancing...
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Surround encoding does the following:
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Lt=L+.707*C+.707*S, Rt=R+.707*C-.707*S
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So S should be extracted as:
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(Lt-Rt)
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But we are splitting the S to two output channels, so we
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must take 3dB off as we split it:
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Ls=Rs=.707*(Lt-Rt)
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Trouble is, Lt could be +1, Rt -1, so possibility that S will
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overflow. So to avoid that, we cut L/R by 3dB (*.707), and S by
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6dB (/2). This keeps the overall balance, but guarantees no
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overflow. */
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// Output front left and right
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out[0] = m[0]*in[0] + m[1]*in[1];
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out[1] = m[2]*in[0] + m[3]*in[1];
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// Low-pass output @ 7kHz
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FIR((&s->lq[i]), s->w, s->dl[wi]);
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// Delay output by d ms
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out[2] = s->dl[ri];
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#ifdef SPLITREAR
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// Low-pass output @ 7kHz
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FIR((&s->rq[i]), s->w, s->dr[wi]);
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// Delay output by d ms
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out[3] = s->dr[ri];
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#else
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out[3] = -out[2];
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#endif
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// Update delay queues indexes
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UPDATEQI(ri);
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UPDATEQI(wi);
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// Calculate and save surround in circular queue
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#ifdef SPLITREAR
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ADDQUE(i, s->rq, s->lq, m[6]*in[0]+m[7]*in[1], m[8]*in[0]+m[9]*in[1]);
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#else
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ADDQUE(i, s->lq, m[4]*in[0]+m[5]*in[1]);
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#endif
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// Next sample...
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in = &in[data->nch];
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out = &out[af->data->nch];
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}
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// Save indexes
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s->i = i; s->ri = ri; s->wi = wi;
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// Set output data
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data->audio = af->data->audio;
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data->len *= 2;
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data->nch = af->data->nch;
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return data;
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}
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static int af_open(af_instance_t* af){
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af->control=control;
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af->uninit=uninit;
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af->play=play;
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af->mul=2;
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af->data=calloc(1,sizeof(af_data_t));
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af->setup=calloc(1,sizeof(af_surround_t));
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if(af->data == NULL || af->setup == NULL)
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return AF_ERROR;
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((af_surround_t*)af->setup)->d = 20;
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return AF_OK;
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}
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af_info_t af_info_surround =
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{
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"Surround decoder filter",
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"surround",
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"Steve Davies <steve@daviesfam.org>",
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"",
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AF_FLAGS_NOT_REENTRANT,
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af_open
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};
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