libaf/af_center.c

   1 /*
   2  * This filter adds a center channel to the audio stream by
   3  * averaging the left and right channel.
   4  * There are two runtime controls one for setting which channel
   5  * to insert the center-audio into called AF_CONTROL_SUB_CH.
   6  *
   7  * FIXME: implement a high-pass filter for better results.
   8  *
   9  * copyright (c) 2005 Alex Beregszaszi
  10  *
  11  * This file is part of MPlayer.
  12  *
  13  * MPlayer is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License as published by
  15  * the Free Software Foundation; either version 2 of the License, or
  16  * (at your option) any later version.
  17  *
  18  * MPlayer is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  * GNU General Public License for more details.
  22  *
  23  * You should have received a copy of the GNU General Public License along
  24  * with MPlayer; if not, write to the Free Software Foundation, Inc.,
  25  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  26  */
  27
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31
  32 #include "af.h"
  33
  34 // Data for specific instances of this filter
  35 typedef struct af_center_s
  36 {
  37   int ch;               // Channel number which to insert the filtered data
  38 }af_center_t;
  39
  40 // Initialization and runtime control
  41 static int control(struct af_instance_s* af, int cmd, void* arg)
  42 {
  43   af_center_t* s   = af->setup;
  44
  45   switch(cmd){
  46   case AF_CONTROL_REINIT:{
  47     // Sanity check
  48     if(!arg) return AF_ERROR;
  49
  50     af->data->rate   = ((af_data_t*)arg)->rate;
  51     af->data->nch    = max(s->ch+1,((af_data_t*)arg)->nch);
  52     af->data->format = AF_FORMAT_FLOAT_NE;
  53     af->data->bps    = 4;
  54
  55     return af_test_output(af,(af_data_t*)arg);
  56   }
  57   case AF_CONTROL_COMMAND_LINE:{
  58     int   ch=1;
  59     sscanf(arg,"%i", &ch);
  60     return control(af,AF_CONTROL_CENTER_CH | AF_CONTROL_SET, &ch);
  61   }
  62   case AF_CONTROL_CENTER_CH | AF_CONTROL_SET: // Requires reinit
  63     // Sanity check
  64     if((*(int*)arg >= AF_NCH) || (*(int*)arg < 0)){
  65       mp_msg(MSGT_AFILTER, MSGL_ERR, "[sub] Center channel number must be between "
  66              " 0 and %i current value is %i\n", AF_NCH-1, *(int*)arg);
  67       return AF_ERROR;
  68     }
  69     s->ch = *(int*)arg;
  70     return AF_OK;
  71   case AF_CONTROL_CENTER_CH | AF_CONTROL_GET:
  72     *(int*)arg = s->ch;
  73     return AF_OK;
  74   }
  75   return AF_UNKNOWN;
  76 }
  77
  78 // Deallocate memory
  79 static void uninit(struct af_instance_s* af)
  80 {
  81     free(af->data);
  82     free(af->setup);
  83 }
  84
  85 // Filter data through filter
  86 static af_data_t* play(struct af_instance_s* af, af_data_t* data)
  87 {
  88   af_data_t*    c   = data;      // Current working data
  89   af_center_t*  s   = af->setup; // Setup for this instance
  90   float*        a   = c->audio;  // Audio data
  91   int           len = c->len/4;  // Number of samples in current audio block
  92   int           nch = c->nch;    // Number of channels
  93   int           ch  = s->ch;     // Channel in which to insert the center audio
  94   register int  i;
  95
  96   // Run filter
  97   for(i=0;i<len;i+=nch){
  98     // Average left and right
  99     a[i+ch] = (a[i]/2) + (a[i+1]/2);
 100   }
 101
 102   return c;
 103 }
 104
 105 // Allocate memory and set function pointers
 106 static int af_open(af_instance_t* af){
 107   af_center_t* s;
 108   af->control=control;
 109   af->uninit=uninit;
 110   af->play=play;
 111   af->mul=1;
 112   af->data=calloc(1,sizeof(af_data_t));
 113   af->setup=s=calloc(1,sizeof(af_center_t));
 114   if(af->data == NULL || af->setup == NULL)
 115     return AF_ERROR;
 116   // Set default values
 117   s->ch = 1;     // Channel nr 2
 118   return AF_OK;
 119 }
 120
 121 // Description of this filter
 122 af_info_t af_info_center = {
 123     "Audio filter for adding a center channel",
 124     "center",
 125     "Alex Beregszaszi",
 126     "",
 127     AF_FLAGS_NOT_REENTRANT,
 128     af_open
 129 };