postfish/mute.c

   1 /*
   2  *
   3  *  postfish
   4  *
   5  *      Copyright (C) 2002-2005 Monty and Xiph.Org
   6  *
   7  *  Postfish is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License as published by
   9  *  the Free Software Foundation; either version 2, or (at your option)
  10  *  any later version.
  11  *
  12  *  Postfish is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License
  18  *  along with Postfish; see the file COPYING.  If not, write to the
  19  *  Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  *
  22  */
  23
  24 #include <sys/types.h>
  25 #include "postfish.h"
  26 #include "mix.h"
  27 #include "mute.h"
  28 #include "window.h"
  29
  30 extern int input_ch;
  31 extern sig_atomic_t *mixpanel_active;
  32
  33 typedef struct {
  34   u_int32_t active_prev;
  35   int active_ch;
  36   int init_state;
  37   float *leftwindow;
  38 } mute_state;
  39
  40 static mute_state channel_state;
  41
  42 int mute_load(void){
  43   memset(&channel_state,0,sizeof(channel_state));
  44   channel_state.active_ch=input_ch;
  45   channel_state.leftwindow=window_get(1,input_size);
  46   return 0;
  47 }
  48
  49 int mute_channel_muted(u_int32_t active,int i){
  50   return(!(active&(1<<i)));
  51 }
  52
  53 time_linkage *mute_read(time_linkage *in){
  54   u_int32_t preval=0,retval=0;
  55   int i,j;
  56
  57   if(!channel_state.init_state)
  58     channel_state.active_prev=in->active;
  59
  60   /* the mute module is responsible for smoothly ramping audio levels
  61      to/from zero and unity upon mute state change */
  62
  63   for(i=0;i<input_ch;i++)
  64     if(mixpanel_active[i])
  65       preval|= (1<<i);
  66
  67   /* the mute module is responsible for smoothly ramping audio levels
  68      to/from zero and unity upon mute state change */
  69   for(i=0;i<input_ch;i++){
  70     float *x=in->data[i];
  71     if(mixpanel_active[i]){
  72       retval|= (1<<i);
  73
  74       if(mute_channel_muted(channel_state.active_prev,i)){
  75         /* mute->active */
  76         for(j=0;j<input_size;j++)
  77           x[j]*=channel_state.leftwindow[j];
  78
  79       }
  80     }else{
  81       if(!mute_channel_muted(channel_state.active_prev,i)){
  82         /* active->mute; ramp to zero and temporarily keep this
  83            channel active for this frame while ramping */
  84
  85         retval|= (1<<i);
  86         for(j=0;j<input_size;j++)
  87           x[j]*=channel_state.leftwindow[input_size-j];
  88
  89       }
  90     }
  91   }
  92
  93   in->active=retval;
  94   channel_state.active_prev=preval;
  95   channel_state.init_state=1;
  96   return(in);
  97 }