mirror of https://github.com/mpv-player/mpv
100 lines
2.9 KiB
C
100 lines
2.9 KiB
C
/*
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* This filter adds a center channel to the audio stream by
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* averaging the left and right channel.
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* There are two runtime controls one for setting which channel
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* to insert the center-audio into called AF_CONTROL_SUB_CH.
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*
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* FIXME: implement a high-pass filter for better results.
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*
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* copyright (c) 2005 Alex Beregszaszi
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*
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* This file is part of MPlayer.
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*
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* MPlayer 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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* MPlayer 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 MPlayer; 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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*/
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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 "common/common.h"
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#include "af.h"
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// Data for specific instances of this filter
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typedef struct af_center_s
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{
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int ch; // Channel number which to insert the filtered data
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}af_center_t;
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// Initialization and runtime control
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static int control(struct af_instance* af, int cmd, void* arg)
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{
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af_center_t* s = af->priv;
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switch(cmd){
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case AF_CONTROL_REINIT:{
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// Sanity check
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if(!arg) return AF_ERROR;
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af->data->rate = ((struct mp_audio*)arg)->rate;
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mp_audio_set_channels_old(af->data, MPMAX(s->ch+1,((struct mp_audio*)arg)->nch));
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mp_audio_set_format(af->data, AF_FORMAT_FLOAT);
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return af_test_output(af,(struct mp_audio*)arg);
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}
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}
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return AF_UNKNOWN;
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}
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// Filter data through filter
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static int filter(struct af_instance* af, struct mp_audio* data, int flags)
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{
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struct mp_audio* c = data; // Current working data
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af_center_t* s = af->priv; // Setup for this instance
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float* a = c->planes[0]; // Audio data
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int nch = c->nch; // Number of channels
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int len = c->samples*c->nch; // Number of samples in current audio block
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int ch = s->ch; // Channel in which to insert the center audio
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register int i;
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// Run filter
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for(i=0;i<len;i+=nch){
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// Average left and right
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a[i+ch] = (a[i]/2) + (a[i+1]/2);
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}
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return 0;
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}
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// Allocate memory and set function pointers
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static int af_open(struct af_instance* af){
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af->control=control;
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af->filter=filter;
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return AF_OK;
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}
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#define OPT_BASE_STRUCT af_center_t
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struct af_info af_info_center = {
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.info = "Audio filter for adding a center channel",
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.name = "center",
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.flags = AF_FLAGS_NOT_REENTRANT,
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.open = af_open,
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.priv_size = sizeof(af_center_t),
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.options = (const struct m_option[]) {
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OPT_INTRANGE("channel", ch, 0, 0, AF_NCH - 1, OPTDEF_INT(1)),
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{0}
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},
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};
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