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         free(af->data);
  50 }
  51
  52 // Filter data through filter
  53 static af_data_t* play(struct af_instance_s* af, af_data_t* data)
  54 {
  55         af_data_t*      c       = data;          // Current working data
  56         float*          a       = c->audio;      // Audio data
  57         int                     len     = c->len/4;      // Number of samples in current audio block
  58         int                     nch     = c->nch;        // Number of channels
  59         register int  i;
  60
  61         /*
  62                 FIXME1 add a low band pass filter to avoid suppressing
  63                 centered bass/drums
  64                 FIXME2 better calculated* attenuation factor
  65         */
  66
  67         for(i=0;i<len;i+=nch)
  68         {
  69                 a[i] = (a[i] - a[i+1]) * 0.7;
  70                 a[i+1]=a[i];
  71         }
  72
  73         return c;
  74 }
  75
  76 // Allocate memory and set function pointers
  77 static int af_open(af_instance_t* af){
  78         af->control     = control;
  79         af->uninit      = uninit;
  80         af->play        = play;
  81         af->mul         = 1;
  82         af->data        = calloc(1,sizeof(af_data_t));
  83
  84         if(af->data == NULL)
  85                 return AF_ERROR;
  86
  87         return AF_OK;
  88 }
  89
  90 // Description of this filter
  91 af_info_t af_info_karaoke = {
  92         "Simple karaoke/voice-removal audio filter",
  93         "karaoke",
  94         "Reynaldo H. Verdejo Pinochet",
  95         "",
  96         AF_FLAGS_NOT_REENTRANT,
  97         af_open
  98 };