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/* This audio output plugin changes the volume of the sound, and can
be used when the mixer doesn't support the PCM channel. The volume
is set in fixed steps between 0 - 2^8. */
#define PLUGIN
// Some limits
#define MIN_S16 -32650
#define MAX_S16 32650
#define MIN_U8 0
#define MAX_U8 255
#define MIN_S8 -128
#define MAX_S8 127
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <inttypes.h>
#include "audio_out.h"
#include "audio_plugin.h"
#include "audio_plugin_internal.h"
#include "afmt.h"
static ao_info_t info =
{
"Volume control audio plugin",
"volume",
"Anders",
""
};
LIBAO_PLUGIN_EXTERN(volume)
// local data
typedef struct pl_volume_s
{
uint16_t volume; // output volume level
int inuse; // This plugin is in use TRUE, FALSE
int format; // sample fomat
} pl_volume_t;
static pl_volume_t pl_volume={0,0,0};
// to set/get/query special features/parameters
static int control(int cmd,void *arg){
switch(cmd){
case AOCONTROL_PLUGIN_SET_LEN:
return CONTROL_OK;
case AOCONTROL_GET_VOLUME:{
if(pl_volume.inuse){
((ao_control_vol_t *)arg)->right=((float)pl_volume.volume)/2.55;
((ao_control_vol_t *)arg)->left=((float)pl_volume.volume)/2.55;
return CONTROL_OK;
}
else
return CONTROL_ERROR;
}
case AOCONTROL_SET_VOLUME:{
if(pl_volume.inuse){
// Calculate avarage between left and right
float vol =2.55*((((ao_control_vol_t *)arg)->right)+(((ao_control_vol_t *)arg)->left))/2;
pl_volume.volume=(uint16_t)vol;
// Volume must be between 0 and 255
if(vol > 255)
pl_volume.volume = 0xFF;
if(vol < 0)
pl_volume.volume = 0;
return CONTROL_OK;
}
else
return CONTROL_ERROR;
}
}
return CONTROL_UNKNOWN;
}
// open & setup audio device
// return: 1=success 0=fail
static int init(){
// Sanity sheck this plugin supports AFMT_U8 and AFMT_S16_LE
switch(ao_plugin_data.format){
case(AFMT_U8):
case(AFMT_S16_NE):
break;
default:
fprintf(stderr,"[pl_volume] Audio format not yet suported \n");
return 0;
}
// Initialize volume to this value
pl_volume.volume=ao_plugin_cfg.pl_volume_volume;
pl_volume.format=ao_plugin_data.format;
/* The inuse flag is used in control to detremine if the return
value since that function always is called from ao_plugin regardless
of wether this plugin is in use or not. */
pl_volume.inuse=1;
// Tell the world what we are up to
printf("[pl_volume] Software volume control in use%s.\n",ao_plugin_cfg.pl_volume_softclip?", soft clipping enabled":"");
return 1;
}
// close plugin
static void uninit(){
pl_volume.inuse=0;
}
// empty buffers
static void reset(){
}
#define SIGN(x) (x>0?1:-1)
// processes 'ao_plugin_data.len' bytes of 'data'
// called for every block of data
static int play(){
register int i=0;
register int vol=pl_volume.volume; // Logarithmic control sounds more natural
vol=(vol*vol*vol)>>12;
// Change the volume.
switch(pl_volume.format){
case(AFMT_U8):{
register uint8_t* data=(uint8_t*)ao_plugin_data.data;
register int x;
for(i=0;i<ao_plugin_data.len;i++){
x=((data[i]-128) * vol) >> 8;
if(x>MAX_S8)
data[i]=MAX_U8;
else if(x<MIN_S8)
data[i]=MIN_U8;
else{
if(ao_plugin_cfg.pl_volume_softclip)
data[i] = ((3*x - ((x*x*x) >> 14)) >> 1) + 128;
else
data[i] = x + 128;
}
}
break;
}
case(AFMT_S16_NE):{
register int len=ao_plugin_data.len>>1;
register int16_t* data=(int16_t*)ao_plugin_data.data;
register int x;
for(i=0;i<len;i++){
x=(data[i] * vol) >> 8;
if(x>MAX_S16)
data[i]=MAX_S16;
else if(x<MIN_S16)
data[i]=MIN_S16;
else{
if(ao_plugin_cfg.pl_volume_softclip){
int64_t t=x*x;
t=(t*x) >> 30;
data[i] = (3*x - (int)t) >> 1;
//data[i] = 2*x - SIGN(x)*((x*x)>>15);
}
else
data[i] = x;
}
}
break;
}
default:
return 0;
}
return 1;
}
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