libaf/af_karaoke.c

   1 /*
   2  * simple voice removal filter
   3  *
   4  * copyright (c) 2006 Reynaldo H. Verdejo Pinochet
   5  * Based on code by Alex Beregszaszi for his 'center' filter.
   6  *
   7  * This file is part of MPlayer.
   8  *
   9  * MPlayer is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * MPlayer is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with MPlayer; if not, write to the Free Software Foundation, Inc.,
  21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  22  */
  23
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27
  28 #include "af.h"
  29
  30 // Data for specific instances of this filter
  31
  32 // Initialization and runtime control
  33 static int control(struct af_instance_s* af, int cmd, void* arg)
  34 {
  35         switch(cmd){
  36                 case AF_CONTROL_REINIT:
  37                 af->data->rate  = ((af_data_t*)arg)->rate;
  38                 af->data->nch   = ((af_data_t*)arg)->nch;
  39                 af->data->format= AF_FORMAT_FLOAT_NE;
  40                 af->data->bps   = 4;
  41                 return af_test_output(af,(af_data_t*)arg);
  42         }
  43         return AF_UNKNOWN;
  44 }
  45
  46 // Deallocate memory
  47 static void uninit(struct af_instance_s* af)
  48 {
  49         if(af->data)
  50                 free(af->data);
  51 }
  52
  53 // Filter data through filter
  54 static af_data_t* play(struct af_instance_s* af, af_data_t* data)
  55 {
  56         af_data_t*      c       = data;          // Current working data
  57         float*          a       = c->audio;      // Audio data
  58         int                     len     = c->len/4;      // Number of samples in current audio block
  59         int                     nch     = c->nch;        // Number of channels
  60         register int  i;
  61
  62         /*
  63                 FIXME1 add a low band pass filter to avoid suppressing
  64                 centered bass/drums
  65                 FIXME2 better calculated* attenuation factor
  66         */
  67
  68         for(i=0;i<len;i+=nch)
  69         {
  70                 a[i] = (a[i] - a[i+1]) * 0.7;
  71                 a[i+1]=a[i];
  72         }
  73
  74         return c;
  75 }
  76
  77 // Allocate memory and set function pointers
  78 static int af_open(af_instance_t* af){
  79         af->control     = control;
  80         af->uninit      = uninit;
  81         af->play        = play;
  82         af->mul         = 1;
  83         af->data        = calloc(1,sizeof(af_data_t));
  84
  85         if(af->data == NULL)
  86                 return AF_ERROR;
  87
  88         return AF_OK;
  89 }
  90
  91 // Description of this filter
  92 af_info_t af_info_karaoke = {
  93         "Simple karaoke/voice-removal audio filter",
  94         "karaoke",
  95         "Reynaldo H. Verdejo Pinochet",
  96         "",
  97         AF_FLAGS_NOT_REENTRANT,
  98         af_open
  99 };