Audio Resample Code. More...

#include <switch.h>

Include dependency graph for switch_resample.h:

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Data Structures
struct	switch_audio_resampler_t
	An audio resampling handle. More...

Macros
#define	switch_normalize_volume(x) if (x > 4) x = 4; if (x < -4) x = -4;

#define	switch_normalize_volume_granular(x) if (x > 13) x = 13; if (x < -13) x = -13;

#define	SWITCH_RESAMPLE_QUALITY 2

#define	switch_resample_create(_n, _fr, _tr, _ts, _q, _c) switch_resample_perform_create(_n, _fr, _tr, _ts, _q, _c, __FILE__, __SWITCH_FUNC__, __LINE__)

#define	switch_resample_calc_buffer_size(_to, _from, _srclen) ((uint32_t)(((float)_to / (float)_from) * (float)_srclen) * 2)

Functions
switch_status_t	switch_resample_perform_create (switch_audio_resampler_t *new_resampler, uint32_t from_rate, uint32_t to_rate, uint32_t to_size, int quality, uint32_t channels, const char file, const char *func, int line)
	Prepare a new resampler handle. More...

void	switch_resample_destroy (switch_audio_resampler_t **resampler)
	Destroy an existing resampler handle. More...

uint32_t	switch_resample_process (switch_audio_resampler_t resampler, int16_t src, uint32_t srclen)
	Resample one float buffer into another using specifications of a given handle. More...

switch_size_t	switch_float_to_short (float f, short s, switch_size_t len)
	Convert an array of floats to an array of shorts. More...

int	switch_char_to_float (char c, float f, int len)
	Convert an array of chars to an array of floats. More...

int	switch_float_to_char (float f, char c, int len)
	Convert an array of floats to an array of chars. More...

int	switch_short_to_float (short s, float f, int len)
	Convert an array of shorts to an array of floats. More...

void	switch_swap_linear (int16_t *buf, int len)
	Perform a byteswap on a buffer of 16 bit samples. More...

void	switch_generate_sln_silence (int16_t *data, uint32_t samples, uint32_t channels, uint32_t divisor)
	Generate static noise. More...

void	switch_change_sln_volume (int16_t *data, uint32_t samples, int32_t vol)
	Change the volume of a signed linear audio frame. More...

void	switch_change_sln_volume_granular (int16_t *data, uint32_t samples, int32_t vol)
	Change the volume of a signed linear audio frame with more granularity. More...

uint32_t	switch_merge_sln (int16_t data, uint32_t samples, int16_t other_data, uint32_t other_samples, int channels)

uint32_t	switch_unmerge_sln (int16_t data, uint32_t samples, int16_t other_data, uint32_t other_samples, int channels)

void	switch_mux_channels (int16_t *data, switch_size_t samples, uint32_t orig_channels, uint32_t channels)

Detailed Description

Audio Resample Code.

This module implements a generic interface for doing audio resampling it currently uses libresample but can be ported to any resample library with a little effort. I decided against making this interface pluggable because there are not many options in terms of resample libraries so it seemed like a waste but I did opt to frontend the interface in case a better way comes along some day. =D

Definition in file switch_resample.h.

Macro Definition Documentation

#define switch_normalize_volume ( x ) if (x > 4) x = 4; if (x < -4) x = -4;

Definition at line 41 of file switch_resample.h.

Referenced by switch_change_sln_volume(), and switch_ivr_process_fh().

#define switch_normalize_volume_granular ( x ) if (x > 13) x = 13; if (x < -13) x = -13;

Definition at line 42 of file switch_resample.h.

Referenced by switch_change_sln_volume_granular().

#define switch_resample_calc_buffer_size	(	_to,
		_from,
		_srclen
	)	((uint32_t)(((float)_to / (float)_from) * (float)_srclen) * 2)

Definition at line 178 of file switch_resample.h.

Referenced by switch_core_session_write_frame(), switch_resample_perform_create(), and switch_resample_process().

#define SWITCH_RESAMPLE_QUALITY 2

Definition at line 46 of file switch_resample.h.

Referenced by switch_core_asr_feed(), switch_core_file_read(), switch_core_file_write(), switch_core_session_read_frame(), switch_core_session_write_frame(), and switch_core_speech_read_tts().

Function Documentation

uint32_t switch_merge_sln	(	int16_t *	data,
		uint32_t	samples,
		int16_t *	other_data,
		uint32_t	other_samples,
		int	channels
	)

Definition at line 231 of file switch_resample.c.

References switch_normalize_to_16bit.

Referenced by eavesdrop_callback().

 {
         int i;
         int32_t x, z;
 
         if (channels == 0) channels = 1;
 
         if (samples > other_samples) {
                 x = other_samples;
         } else {
                 x = samples;
         }
 
         for (i = 0; i < x * channels; i++) {
                 z = data[i] + other_data[i];
                 switch_normalize_to_16bit(z);
                 data[i] = (int16_t) z;
         }
 
         return x;
 }

void switch_mux_channels	(	int16_t *	data,
		switch_size_t	samples,
		uint32_t	orig_channels,
		uint32_t	channels
	)

Definition at line 274 of file switch_resample.c.

References switch_assert, switch_normalize_to_16bit, and switch_zmalloc.

Referenced by switch_core_file_read(), switch_core_session_read_frame(), switch_core_session_write_frame(), switch_core_speech_read_tts(), switch_ivr_eavesdrop_session(), and teletone_handler().

 {
         switch_size_t i = 0;
         uint32_t j = 0;
 
         switch_assert(channels < 11);
 
         if (orig_channels > channels) {
                 for (i = 0; i < samples; i++) {
                         int32_t z = 0;
                         for (j = 0; j < orig_channels; j++) {
                                 z += data[i * orig_channels + j];
                                 switch_normalize_to_16bit(z);
                                 data[i] = (int16_t) z;
                         }
                 }
         } else if (orig_channels < channels) {
 
                 /* interesting problem... take a give buffer and double up every sample in the buffer without using any other buffer.....
                    This way beats the other i think bacause there is no malloc but I do have to copy the data twice */
 #if 1
                 uint32_t k = 0, len = samples * orig_channels;
 
                 for (i = 0; i < len; i++) {
                         data[i+len] = data[i];
                 }
 
                 for (i = 0; i < samples; i++) {
                         for (j = 0; j < channels; j++) { 
                                 data[k++] = data[i + samples];
                         }
                 }
 
 #else 
                 uint32_t k = 0, len = samples * 2 * orig_channels;
                 int16_t *orig = NULL;
 
                 switch_zmalloc(orig, len);
                 memcpy(orig, data, len);
 
                 for (i = 0; i < samples; i++) {
                         for (j = 0; j < channels; j++) { 
                                 data[k++] = orig[i];
                         }
                 }
                 
                 free(orig);
 #endif
 
         }
 }

uint32_t switch_unmerge_sln	(	int16_t *	data,
		uint32_t	samples,
		int16_t *	other_data,
		uint32_t	other_samples,
		int	channels
	)

Definition at line 254 of file switch_resample.c.

Referenced by switch_core_session_read_frame().

 {
         int i;
         int32_t x;
 
         if (channels == 0) channels = 1;
 
         if (samples > other_samples) {
                 x = other_samples;
         } else {
                 x = samples;
         }
 
         for (i = 0; i < x * channels; i++) {
                 data[i] -= other_data[i];
         }
 
         return x;
 }

Data Structures

Macros

Functions

Detailed Description

Macro Definition Documentation

Function Documentation