libaf/af_karaoke.c

   1 /*
   2     (c)2006 MPlayer / Reynaldo H. Verdejo Pinochet
   3         Based on code by Alex Beregszaszi for his 'center' filter
   4
   5     License: GPL
   6
   7     Simple voice removal filter
   8 */
   9
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13
  14 #include "af.h"
  15
  16 // Data for specific instances of this filter
  17
  18 // Initialization and runtime control
  19 static int control(struct af_instance_s* af, int cmd, void* arg)
  20 {
  21         switch(cmd){
  22                 case AF_CONTROL_REINIT:
  23                 af->data->rate  = ((af_data_t*)arg)->rate;
  24                 af->data->nch   = ((af_data_t*)arg)->nch;
  25                 af->data->format= AF_FORMAT_FLOAT_NE;
  26                 af->data->bps   = 4;
  27                 return af_test_output(af,(af_data_t*)arg);
  28         }
  29         return AF_UNKNOWN;
  30 }
  31
  32 // Deallocate memory
  33 static void uninit(struct af_instance_s* af)
  34 {
  35         if(af->data)
  36                 free(af->data);
  37 }
  38
  39 // Filter data through filter
  40 static af_data_t* play(struct af_instance_s* af, af_data_t* data)
  41 {
  42         af_data_t*      c       = data;          // Current working data
  43         float*          a       = c->audio;      // Audio data
  44         int                     len     = c->len/4;      // Number of samples in current audio block
  45         int                     nch     = c->nch;        // Number of channels
  46         register int  i;
  47
  48         /*
  49                 FIXME1 add a low band pass filter to avoid suppressing
  50                 centered bass/drums
  51                 FIXME2 better calculated* attenuation factor
  52         */
  53
  54         for(i=0;i<len;i+=nch)
  55         {
  56                 a[i] = (a[i] - a[i+1]) * 0.7;
  57                 a[i+1]=a[i];
  58         }
  59
  60         return c;
  61 }
  62
  63 // Allocate memory and set function pointers
  64 static int af_open(af_instance_t* af){
  65         af->control     = control;
  66         af->uninit      = uninit;
  67         af->play        = play;
  68         af->mul         = 1;
  69         af->data        = calloc(1,sizeof(af_data_t));
  70
  71         if(af->data == NULL)
  72                 return AF_ERROR;
  73
  74         return AF_OK;
  75 }
  76
  77 // Description of this filter
  78 af_info_t af_info_karaoke = {
  79         "Simple karaoke/voice-removal audio filter",
  80         "karaoke",
  81         "Reynaldo H. Verdejo Pinochet",
  82         "",
  83         AF_FLAGS_NOT_REENTRANT,
  84         af_open
  85 };