mpv/libaf/af.h

#ifndef __aop_h__
#define __aop_h__

struct af_instance_s;

// Audio data chunk
typedef struct af_data_s
{
  void* audio;  // data buffer
  int len;      // buffer length
  int rate;	// sample rate
  int nch;	// number of channels
  int format;	// format
  int bps; 	// bytes per sample
} af_data_t;

// Fraction, used to calculate buffer lengths
typedef struct frac_s
{
  int n; // Numerator
  int d; // Denominator
} frac_t;

/* Audio filter information not specific for current instance, but for
   a specific filter */ 
typedef struct af_info_s 
{
  const char *info;
  const char *name;
  const char *author;
  const char *comment;
  int (*open)(struct af_instance_s* vf);
} af_info_t;

// Linked list of audio filters
typedef struct af_instance_s
{
  af_info_t* info;
  int (*control)(struct af_instance_s* af, int cmd, void* arg);
  void (*uninit)(struct af_instance_s* af);
  af_data_t* (*play)(struct af_instance_s* af, af_data_t* data);
  void* setup;	  // setup data for this specific instance and filter
  af_data_t* data; // configuration for outgoing data stream
  struct af_instance_s* next;
  struct af_instance_s* prev;  
  frac_t mul; /* length multiplier: how much does this instance change
		 the length of the buffer. */
}af_instance_t;

/*********************************************
// Control parameters 
*/

/* The control system is divided into 3 levels 
   mandatory calls 	 - all filters must answer to all of these
   optional calls  	 - are optional
   filter specific calls - applies only to some filters
*/

#define AF_CONTROL_MANDATORY_BASE	0
#define AF_CONTROL_OPTIONAL_BASE	100
#define AF_CONTROL_FILTER_SPECIFIC_BASE	200

// MANDATORY CALLS

/* Reinitialize filter. The optional argument contains the new
   configuration in form of a af_data_t struct. If the filter does not
   support the new format the struct should be changed and AF_FALSE
   should be returned. If the incoming and outgoing data streams are
   identical the filter can return AF_DETACH. This will remove the
   filter. */
#define AF_CONTROL_REINIT  		1 + AF_CONTROL_MANDATORY_BASE

// OPTIONAL CALLS


// FILTER SPECIFIC CALLS

// Set output rate in resample
#define AF_CONTROL_RESAMPLE		1 + AF_CONTROL_FILTER_SPECIFIC_BASE
// Set output format in format
#define AF_CONTROL_FORMAT		2 + AF_CONTROL_FILTER_SPECIFIC_BASE
// Set number of output channels in channels
#define AF_CONTROL_CHANNELS		3 + AF_CONTROL_FILTER_SPECIFIC_BASE
// Set delay length in delay
#define AF_CONTROL_SET_DELAY_LEN	4 + AF_CONTROL_FILTER_SPECIFIC_BASE
/*********************************************
// Return values
*/

#define AF_DETACH   2
#define AF_OK       1
#define AF_TRUE     1
#define AF_FALSE    0
#define AF_UNKNOWN -1
#define AF_ERROR   -2
#define AF_NA      -3


/*********************************************
// Command line configuration switches
*/
typedef struct af_cfg_s{
  int rate;
  int format;
  int bps;
  int force;
  char** list;
}af_cfg_t;


// Export functions

/* Init read configuration and create filter list accordingly. In and
   out contains the format of the current movie and the formate of the
   prefered output respectively */
int af_init(af_data_t* in, af_data_t* out);
// Uninit and remove all filters
void af_uninit();
// Filter data chunk through the filters in the list
af_data_t* af_play(af_data_t* data);
/* Calculate how long the output from the filters will be given the
   input length "len" */
int af_outputlen(int len);
/* Calculate how long the input to the filters should be to produce a
   certain output length, i.e. the return value of this function is
   the input length required to produce the output length "len". */
int af_inputlen(int len);



// Helper functions and macros used inside the audio filters

/* Helper function called by the macro with the same name only to be
   called from inside filters */
int af_resize_local_buffer(af_instance_t* af, af_data_t* data);

/* Helper function used to calculate the exact buffer length needed
   when buffers are resized */
int af_lencalc(frac_t mul, int len);

/* Memory reallocation macro: if a local buffer is used (i.e. if the
   filter doesn't operate on the incoming buffer this macro must be
   called to ensure the buffer is big enough. */
#define RESIZE_LOCAL_BUFFER(a,d)\
((af->data->len < af_lencalc(af->mul,data->len))?af_resize_local_buffer(af,data):AF_OK)

#ifndef min
#define min(a,b)(((a)>(b))?(b):(a))
#endif

#ifndef max
#define max(a,b)(((a)>(b))?(a):(b))
#endif

#ifndef AUDIO_FILTER
extern af_cfg_t af_cfg;
#endif /* AUDIO_FILTER */

#endif