mirror of https://github.com/mpv-player/mpv
143 lines
4.3 KiB
C
143 lines
4.3 KiB
C
/*
|
|
* 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 "common/common.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->priv;
|
|
|
|
switch(cmd){
|
|
case AF_CONTROL_REINIT:{
|
|
// Sanity check
|
|
if(!arg) return AF_ERROR;
|
|
|
|
af->data->rate = ((struct mp_audio*)arg)->rate;
|
|
mp_audio_set_channels_old(af->data, MPMAX(s->ch+1,((struct mp_audio*)arg)->nch));
|
|
mp_audio_set_format(af->data, AF_FORMAT_FLOAT);
|
|
|
|
// 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);
|
|
}
|
|
}
|
|
return AF_UNKNOWN;
|
|
}
|
|
|
|
#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 int filter(struct af_instance* af, struct mp_audio* data, int flags)
|
|
{
|
|
struct mp_audio* c = data; // Current working data
|
|
af_sub_t* s = af->priv; // Setup for this instance
|
|
float* a = c->planes[0]; // Audio data
|
|
int len = c->samples*c->nch; // 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 0;
|
|
}
|
|
|
|
// Allocate memory and set function pointers
|
|
static int af_open(struct af_instance* af){
|
|
af->control=control;
|
|
af->filter=filter;
|
|
return AF_OK;
|
|
}
|
|
|
|
#define OPT_BASE_STRUCT af_sub_t
|
|
struct af_info af_info_sub = {
|
|
.info = "Audio filter for adding a sub-base channel",
|
|
.name = "sub",
|
|
.flags = AF_FLAGS_NOT_REENTRANT,
|
|
.open = af_open,
|
|
.priv_size = sizeof(af_sub_t),
|
|
.options = (const struct m_option[]) {
|
|
OPT_FLOATRANGE("fc", fc, 0, 20, 300, OPTDEF_FLOAT(60.0)),
|
|
OPT_INTRANGE("ch", ch, 0, 0, AF_NCH - 1, OPTDEF_INT(5)),
|
|
{0}
|
|
},
|
|
};
|