samplerate.h

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/*
** Copyright (c) 2002-2016, Erik de Castro Lopo <erikd@mega-nerd.com>
** All rights reserved.
**
** This code is released under 2-clause BSD license. Please see the
** file at : https://github.com/erikd/libsamplerate/blob/master/COPYING
*/
 
/*
** API documentation is available here:
**     http://www.mega-nerd.com/SRC/api.html
*/
 
#ifndef SAMPLERATE_H
#define SAMPLERATE_H
 
#ifdef __cplusplus
extern "C" {
#endif  /* __cplusplus */
 
 
/* Opaque data type SRC_STATE. */
typedef struct SRC_STATE_tag SRC_STATE ;
 
/* SRC_DATA is used to pass data to src_simple() and src_process(). */
typedef struct
{   const float *data_in ;
    float    *data_out ;
 
    long    input_frames, output_frames ;
    long    input_frames_used, output_frames_gen ;
 
    int     end_of_input ;
 
    double  src_ratio ;
} SRC_DATA ;
 
/*
** User supplied callback function type for use with src_callback_new()
** and src_callback_read(). First parameter is the same pointer that was
** passed into src_callback_new(). Second parameter is pointer to a
** pointer. The user supplied callback function must modify *data to
** point to the start of the user supplied float array. The user supplied
** function must return the number of frames that **data points to.
*/
 
typedef long (*src_callback_t) (void *cb_data, float **data) ;
 
/*
**  Standard initialisation function : return an anonymous pointer to the
**  internal state of the converter. Choose a converter from the enums below.
**  Error returned in *error.
*/
 
SRC_STATE* src_new (int converter_type, int channels, int *error) ;
 
/*
**  Initilisation for callback based API : return an anonymous pointer to the
**  internal state of the converter. Choose a converter from the enums below.
**  The cb_data pointer can point to any data or be set to NULL. Whatever the
**  value, when processing, user supplied function "func" gets called with
**  cb_data as first parameter.
*/
 
SRC_STATE* src_callback_new (src_callback_t func, int converter_type, int channels,
                int *error, void* cb_data) ;
 
/*
**  Cleanup all internal allocations.
**  Always returns NULL.
*/
 
SRC_STATE* src_delete (SRC_STATE *state) ;
 
/*
**  Standard processing function.
**  Returns non zero on error.
*/
 
int src_process (SRC_STATE *state, SRC_DATA *data) ;
 
/*
**  Callback based processing function. Read up to frames worth of data from
**  the converter int *data and return frames read or -1 on error.
*/
long src_callback_read (SRC_STATE *state, double src_ratio, long frames, float *data) ;
 
/*
**  Simple interface for performing a single conversion from input buffer to
**  output buffer at a fixed conversion ratio.
**  Simple interface does not require initialisation as it can only operate on
**  a single buffer worth of audio.
*/
 
int src_simple (SRC_DATA *data, int converter_type, int channels) ;
 
/*
** This library contains a number of different sample rate converters,
** numbered 0 through N.
**
** Return a string giving either a name or a more full description of each
** sample rate converter or NULL if no sample rate converter exists for
** the given value. The converters are sequentially numbered from 0 to N.
*/
 
const char *src_get_name (int converter_type) ;
const char *src_get_description (int converter_type) ;
const char *src_get_version (void) ;
 
/*
**  Set a new SRC ratio. This allows step responses
**  in the conversion ratio.
**  Returns non zero on error.
*/
 
int src_set_ratio (SRC_STATE *state, double new_ratio) ;
 
/*
**  Get the current channel count.
**  Returns negative on error, positive channel count otherwise
*/
 
int src_get_channels (SRC_STATE *state) ;
 
/*
**  Reset the internal SRC state.
**  Does not modify the quality settings.
**  Does not free any memory allocations.
**  Returns non zero on error.
*/
 
int src_reset (SRC_STATE *state) ;
 
/*
** Return TRUE if ratio is a valid conversion ratio, FALSE
** otherwise.
*/
 
int src_is_valid_ratio (double ratio) ;
 
/*
**  Return an error number.
*/
 
int src_error (SRC_STATE *state) ;
 
/*
**  Convert the error number into a string.
*/
const char* src_strerror (int error) ;
 
/*
** The following enums can be used to set the interpolator type
** using the function src_set_converter().
*/
 
enum
{
    SRC_SINC_BEST_QUALITY       = 0,
    SRC_SINC_MEDIUM_QUALITY     = 1,
    SRC_SINC_FASTEST            = 2,
    SRC_ZERO_ORDER_HOLD         = 3,
    SRC_LINEAR                  = 4,
} ;
 
/*
** Extra helper functions for converting from short to float and
** back again.
*/
 
void src_short_to_float_array (const short *in, float *out, int len) ;
void src_float_to_short_array (const float *in, short *out, int len) ;
 
void src_int_to_float_array (const int *in, float *out, int len) ;
void src_float_to_int_array (const float *in, int *out, int len) ;
 
 
#ifdef __cplusplus
}       /* extern "C" */
#endif  /* __cplusplus */
 
#endif  /* SAMPLERATE_H */