mpv/libaf/af_delay.c

/* This audio filter delays the output signal for the different
   channels and can be used for simple position panning. Extension for
   this filter would be a reverb.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>

#include "af.h"

#define L 65536

#define UPDATEQI(qi) qi=(qi+1)&(L-1)

// Data for specific instances of this filter
typedef struct af_delay_s
{
  void* q[AF_NCH];   	// Circular queues used for delaying audio signal
  int 	wi[AF_NCH];  	// Write index
  int 	ri;		// Read index
  float	d[AF_NCH];   	// Delay [ms] 	
}af_delay_t;

// Initialization and runtime control
static int control(struct af_instance_s* af, int cmd, void* arg)
{
  af_delay_t* s = af->setup;
  switch(cmd){
  case AF_CONTROL_REINIT:{
    int i;

    // Free prevous delay queues
    for(i=0;i<af->data->nch;i++){
      if(s->q[i])
	free(s->q[i]);
    }

    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;

    // Allocate new delay queues
    for(i=0;i<af->data->nch;i++){
      s->q[i] = calloc(L,af->data->bps);
      if(NULL == s->q[i])
	af_msg(AF_MSG_FATAL,"[delay] Out of memory\n");
    }

    return control(af,AF_CONTROL_DELAY_LEN | AF_CONTROL_SET,s->d);
  }
  case AF_CONTROL_COMMAND_LINE:{
    int n = 1;
    int i = 0;
    char* cl = arg;
    while(n && i < AF_NCH ){
      sscanf(cl,"%f:%n",&s->d[i],&n);
      if(n==0 || cl[n-1] == '\0')
	break;
      cl=&cl[n];
      i++;
    }
    return AF_OK;
  }
  case AF_CONTROL_DELAY_LEN | AF_CONTROL_SET:{
    int i;
    if(AF_OK != af_from_ms(AF_NCH, arg, s->wi, af->data->rate, 0.0, 1000.0))
      return AF_ERROR;
    s->ri = 0;
    for(i=0;i<AF_NCH;i++){
      af_msg(AF_MSG_DEBUG0,"[delay] Channel %i delayed by %0.3fms\n",
	     i,clamp(s->d[i],0.0,1000.0));
      af_msg(AF_MSG_DEBUG1,"[delay] Channel %i delayed by %i samples\n",
	     i,s->wi[i]);
    }
    return AF_OK;
  }
  case AF_CONTROL_DELAY_LEN | AF_CONTROL_GET:{
    int i;
    for(i=0;i<AF_NCH;i++){
      if(s->ri > s->wi[i])
	s->wi[i] = L - (s->ri - s->wi[i]);
      else
	s->wi[i] = s->wi[i] - s->ri;
    }
    return af_to_ms(AF_NCH, s->wi, arg, af->data->rate);
  }
  }
  return AF_UNKNOWN;
}

// Deallocate memory 
static void uninit(struct af_instance_s* af)
{
  int i;
  if(af->data)
    free(af->data);
  for(i=0;i<AF_NCH;i++)
    if(((af_delay_t*)(af->setup))->q[i])
      free(((af_delay_t*)(af->setup))->q[i]);
  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_delay_t*  	s   = af->setup; // Setup for this instance
  int 		nch = c->nch;	 // Number of channels
  int		len = c->len/c->bps; // Number of sample in data chunk
  int		ri  = 0;
  int 		ch,i;
  for(ch=0;ch<nch;ch++){
    switch(c->bps){
    case 1:{
      int8_t* a = c->audio;
      int8_t* q = s->q[ch]; 
      int wi = s->wi[ch];
      ri = s->ri;
      for(i=ch;i<len;i+=nch){
	q[wi] = a[i];
	a[i]  = q[ri];
	UPDATEQI(wi);
	UPDATEQI(ri);
      }
      s->wi[ch] = wi;
      break;
    }
    case 2:{
      int16_t* a = c->audio;
      int16_t* q = s->q[ch]; 
      int wi = s->wi[ch];
      ri = s->ri;
      for(i=ch;i<len;i+=nch){
	q[wi] = a[i];
	a[i]  = q[ri];
	UPDATEQI(wi);
	UPDATEQI(ri);
      }
      s->wi[ch] = wi;
      break;
    }
    case 4:{
      int32_t* a = c->audio;
      int32_t* q = s->q[ch]; 
      int wi = s->wi[ch];
      ri = s->ri;
      for(i=ch;i<len;i+=nch){
	q[wi] = a[i];
	a[i]  = q[ri];
	UPDATEQI(wi);
	UPDATEQI(ri);
      }
      s->wi[ch] = wi;
      break;
    }
    }
  }
  s->ri = ri;
  return c;
}

// Allocate memory and set function pointers
static int af_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,
    af_open
};