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/* This audio filter doesn't really do anything useful but serves an
example of how audio filters work. It delays the output signal by
the number of seconds set by delay=n where n is the number of
seconds.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "af.h"
// Data for specific instances of this filter
typedef struct af_delay_s
{
void* buf; // data block used for delaying audio signal
int len; // local buffer length
float tlen; // Delay in seconds
}af_delay_t;
// Initialization and runtime control
static int control(struct af_instance_s* af, int cmd, void* arg)
{
switch(cmd){
case AF_CONTROL_REINIT:{
af->data->rate = ((af_data_t*)arg)->rate;
af->data->nch = ((af_data_t*)arg)->nch;
af->data->format = ((af_data_t*)arg)->format;
af->data->bps = ((af_data_t*)arg)->bps;
return af->control(af,AF_CONTROL_DELAY_SET_LEN,&((af_delay_t*)af->setup)->tlen);
}
case AF_CONTROL_COMMAND_LINE:{
float d = 0;
sscanf((char*)arg,"%f",&d);
return af->control(af,AF_CONTROL_DELAY_SET_LEN,&d);
}
case AF_CONTROL_DELAY_SET_LEN:{
af_delay_t* s = (af_delay_t*)af->setup;
void* bt = s->buf; // Old buffer
int lt = s->len; // Old len
if(*((float*)arg) > 30 || *((float*)arg) < 0){
af_msg(AF_MSG_ERROR,"Error setting delay length in af_delay. Delay must be between 0s and 30s\n");
s->len=0;
s->tlen=0.0;
af->delay=0.0;
return AF_ERROR;
}
// Set new len and allocate new buffer
s->tlen = *((float*)arg);
af->delay = s->tlen * 1000.0;
s->len = af->data->rate*af->data->bps*af->data->nch*(int)s->tlen;
s->buf = malloc(s->len);
af_msg(AF_MSG_DEBUG0,"[delay] Delaying audio output by %0.2fs\n",s->tlen);
af_msg(AF_MSG_DEBUG1,"[delay] Delaying audio output by %i bytes\n",s->len);
// Out of memory error
if(!s->buf){
s->len = 0;
free(bt);
return AF_ERROR;
}
// Clear the new buffer
memset(s->buf, 0, s->len);
/* Copy old buffer to avoid click in output
sound (at least most of it) and release it */
if(bt){
memcpy(s->buf,bt,min(lt,s->len));
free(bt);
}
return AF_OK;
}
}
return AF_UNKNOWN;
}
// Deallocate memory
static void uninit(struct af_instance_s* af)
{
if(af->data->audio)
free(af->data->audio);
if(af->data)
free(af->data);
if(((af_delay_t*)(af->setup))->buf)
free(((af_delay_t*)(af->setup))->buf);
if(af->setup)
free(af->setup);
}
// Filter data through filter
static af_data_t* play(struct af_instance_s* af, af_data_t* data)
{
af_data_t* c = data; // Current working data
af_data_t* l = af->data; // Local data
af_delay_t* s = (af_delay_t*)af->setup; // Setup for this instance
if(AF_OK != RESIZE_LOCAL_BUFFER(af , data))
return NULL;
if(s->len > c->len){ // Delay bigger than buffer
// Copy beginning of buffer to beginning of output buffer
memcpy(l->audio,s->buf,c->len);
// Move buffer left
memmove(s->buf,s->buf+c->len,s->len-c->len);
// Save away current audio to end of buffer
memcpy(s->buf+s->len-c->len,c->audio,c->len);
}
else{
// Copy end of previous block to beginning of output buffer
memcpy(l->audio,s->buf,s->len);
// Copy current block except end
memcpy(l->audio+s->len,c->audio,c->len-s->len);
// Save away end of current block for next call
memcpy(s->buf,c->audio+c->len-s->len,s->len);
}
// Set output data
c->audio=l->audio;
return c;
}
// Allocate memory and set function pointers
static int open(af_instance_t* af){
af->control=control;
af->uninit=uninit;
af->play=play;
af->mul.n=1;
af->mul.d=1;
af->data=calloc(1,sizeof(af_data_t));
af->setup=calloc(1,sizeof(af_delay_t));
if(af->data == NULL || af->setup == NULL)
return AF_ERROR;
return AF_OK;
}
// Description of this filter
af_info_t af_info_delay = {
"Delay audio filter",
"delay",
"Anders",
"",
AF_FLAGS_REENTRANT,
open
};
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