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Diffstat (limited to 'audio/filter/af_sub.c')
| -rw-r--r-- | audio/filter/af_sub.c | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/audio/filter/af_sub.c b/audio/filter/af_sub.c new file mode 100644 index 0000000000..4af28d9141 --- /dev/null +++ b/audio/filter/af_sub.c @@ -0,0 +1,188 @@ +/* + * Copyright (C) 2002 Anders Johansson ajh@watri.uwa.edu.au + * + * This file is part of MPlayer. + * + * MPlayer is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * MPlayer is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with MPlayer; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +/* This filter adds a sub-woofer channels to the audio stream by + averaging the left and right channel and low-pass filter them. The + low-pass filter is implemented as a 4th order IIR Butterworth + filter, with a variable cutoff frequency between 10 and 300 Hz. The + filter gives 24dB/octave attenuation. There are two runtime + controls one for setting which channel to insert the sub-audio into + called AF_CONTROL_SUB_CH and one for setting the cutoff frequency + called AF_CONTROL_SUB_FC. +*/ + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#include "af.h" +#include "dsp.h" + +// Q value for low-pass filter +#define Q 1.0 + +// Analog domain biquad section +typedef struct{ + float a[3]; // Numerator coefficients + float b[3]; // Denominator coefficients +} biquad_t; + +// S-parameters for designing 4th order Butterworth filter +static biquad_t sp[2] = {{{1.0,0.0,0.0},{1.0,0.765367,1.0}}, + {{1.0,0.0,0.0},{1.0,1.847759,1.0}}}; + +// Data for specific instances of this filter +typedef struct af_sub_s +{ + float w[2][4]; // Filter taps for low-pass filter + float q[2][2]; // Circular queues + float fc; // Cutoff frequency [Hz] for low-pass filter + float k; // Filter gain; + int ch; // Channel number which to insert the filtered data + +}af_sub_t; + +// Initialization and runtime control +static int control(struct af_instance* af, int cmd, void* arg) +{ + af_sub_t* s = af->setup; + + switch(cmd){ + case AF_CONTROL_REINIT:{ + // Sanity check + if(!arg) return AF_ERROR; + + af->data->rate = ((struct mp_audio*)arg)->rate; + af->data->nch = max(s->ch+1,((struct mp_audio*)arg)->nch); + af->data->format = AF_FORMAT_FLOAT_NE; + af->data->bps = 4; + + // Design low-pass filter + s->k = 1.0; + if((-1 == af_filter_szxform(sp[0].a, sp[0].b, Q, s->fc, + (float)af->data->rate, &s->k, s->w[0])) || + (-1 == af_filter_szxform(sp[1].a, sp[1].b, Q, s->fc, + (float)af->data->rate, &s->k, s->w[1]))) + return AF_ERROR; + return af_test_output(af,(struct mp_audio*)arg); + } + case AF_CONTROL_COMMAND_LINE:{ + int ch=5; + float fc=60.0; + sscanf(arg,"%f:%i", &fc , &ch); + if(AF_OK != control(af,AF_CONTROL_SUB_CH | AF_CONTROL_SET, &ch)) + return AF_ERROR; + return control(af,AF_CONTROL_SUB_FC | AF_CONTROL_SET, &fc); + } + case AF_CONTROL_SUB_CH | AF_CONTROL_SET: // Requires reinit + // Sanity check + if((*(int*)arg >= AF_NCH) || (*(int*)arg < 0)){ + mp_msg(MSGT_AFILTER, MSGL_ERR, "[sub] Subwoofer channel number must be between " + " 0 and %i current value is %i\n", AF_NCH-1, *(int*)arg); + return AF_ERROR; + } + s->ch = *(int*)arg; + return AF_OK; + case AF_CONTROL_SUB_CH | AF_CONTROL_GET: + *(int*)arg = s->ch; + return AF_OK; + case AF_CONTROL_SUB_FC | AF_CONTROL_SET: // Requires reinit + // Sanity check + if((*(float*)arg > 300) || (*(float*)arg < 20)){ + mp_msg(MSGT_AFILTER, MSGL_ERR, "[sub] Cutoff frequency must be between 20Hz and" + " 300Hz current value is %0.2f",*(float*)arg); + return AF_ERROR; + } + // Set cutoff frequency + s->fc = *(float*)arg; + return AF_OK; + case AF_CONTROL_SUB_FC | AF_CONTROL_GET: + *(float*)arg = s->fc; + return AF_OK; + } + return AF_UNKNOWN; +} + +// Deallocate memory +static void uninit(struct af_instance* af) +{ + free(af->data); + free(af->setup); +} + +#ifndef IIR +#define IIR(in,w,q,out) { \ + float h0 = (q)[0]; \ + float h1 = (q)[1]; \ + float hn = (in) - h0 * (w)[0] - h1 * (w)[1]; \ + out = hn + h0 * (w)[2] + h1 * (w)[3]; \ + (q)[1] = h0; \ + (q)[0] = hn; \ +} +#endif + +// Filter data through filter +static struct mp_audio* play(struct af_instance* af, struct mp_audio* data) +{ + struct mp_audio* c = data; // Current working data + af_sub_t* s = af->setup; // Setup for this instance + float* a = c->audio; // Audio data + int len = c->len/4; // Number of samples in current audio block + int nch = c->nch; // Number of channels + int ch = s->ch; // Channel in which to insert the sub audio + register int i; + + // Run filter + for(i=0;i<len;i+=nch){ + // Average left and right + register float x = 0.5 * (a[i] + a[i+1]); + IIR(x * s->k, s->w[0], s->q[0], x); + IIR(x , s->w[1], s->q[1], a[i+ch]); + } + + return c; +} + +// Allocate memory and set function pointers +static int af_open(struct af_instance* af){ + af_sub_t* s; + af->control=control; + af->uninit=uninit; + af->play=play; + af->mul=1; + af->data=calloc(1,sizeof(struct mp_audio)); + af->setup=s=calloc(1,sizeof(af_sub_t)); + if(af->data == NULL || af->setup == NULL) + return AF_ERROR; + // Set default values + s->ch = 5; // Channel nr 6 + s->fc = 60; // Cutoff frequency 60Hz + return AF_OK; +} + +// Description of this filter +struct af_info af_info_sub = { + "Audio filter for adding a sub-base channel", + "sub", + "Anders", + "", + AF_FLAGS_NOT_REENTRANT, + af_open +}; |