samplerate.h

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/*
** Copyright (C) 2002-2004 Erik de Castro Lopo <[email protected]>
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
*/

/*
** 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
{ float *data_in, *data_out ;

 long input_frames, output_frames ;
 long input_frames_used, output_frames_gen ;

 int end_of_input ;

 double src_ratio ;
} SRC_DATA ;

/* SRC_CB_DATA is used with callback based API. */
typedef struct
{ long frames ;
 float *data_in ;
} SRC_CB_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) ;

/*
** 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) ;


#ifdef __cplusplus
} /* extern "C" */
#endif /* __cplusplus */

#endif /* SAMPLERATE_H */

/*
** Do not edit or modify anything in this comment block.
** The arch-tag line is a file identity tag for the GNU Arch
** revision control system.
**
** arch-tag: 5421ef3e-c898-4ec3-8671-ea03d943ee00
*/