switch_resample.h File Reference

Audio Resample Code. More...

#include <switch.h>

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Data Structures
struct	switch_audio_resampler_t
	An audio resampling handle. More...
Defines
#define	switch_normalize_volume(x)   if (x > 4) x = 4; if (x < -4) x = -4;
#define	switch_normalize_volume_granular(x)   if (x > 12) x = 12; if (x < -12) x = -12;
#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__)
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.
void	switch_resample_destroy (switch_audio_resampler_t **resampler)
	Destroy an existing resampler handle.
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.
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.
int	switch_char_to_float (char *c, float *f, int len)
	Convert an array of chars to an array of floats.
int	switch_float_to_char (float *f, char *c, int len)
	Convert an array of floats to an array of chars.
int	switch_short_to_float (short *s, float *f, int len)
	Convert an array of shorts to an array of floats.
void	switch_swap_linear (int16_t *buf, int len)
	Perform a byteswap on a buffer of 16 bit samples.
void	switch_generate_sln_silence (int16_t *data, uint32_t samples, uint32_t divisor)
	Generate static noise.
void	switch_change_sln_volume (int16_t *data, uint32_t samples, int32_t vol)
	Change the volume of a signed linear audio frame.
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.
uint32_t	switch_merge_sln (int16_t *data, uint32_t samples, int16_t *other_data, uint32_t other_samples)
uint32_t	switch_unmerge_sln (int16_t *data, uint32_t samples, int16_t *other_data, uint32_t other_samples)
void	switch_mux_channels (int16_t *data, switch_size_t samples, uint32_t channels)

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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.

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Define 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 > 12) x = 12; if (x < -12) x = -12;

Definition at line 42 of file switch_resample.h.

Referenced by switch_change_sln_volume_granular().

#define SWITCH_RESAMPLE_QUALITY   2

Definition at line 46 of file switch_resample.h.

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

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Function Documentation

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

Definition at line 235 of file switch_resample.c.

References switch_normalize_to_16bit.

Referenced by eavesdrop_callback().

{
        int i;
        int32_t x, z;

        if (samples > other_samples) {
                x = other_samples;
        } else {
                x = samples;
        }

        for (i = 0; i < x; 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	channels
	)

Definition at line 274 of file switch_resample.c.

References buf, switch_normalize_to_16bit, and switch_zmalloc.

Referenced by switch_core_file_read().

{
        int16_t *buf;
        switch_size_t len = samples * sizeof(int16_t);
        switch_size_t i = 0;
        uint32_t j = 0, k = 0;

        switch_zmalloc(buf, len);

        for (i = 0; i < samples; i++) {
                for (j = 0; j < channels; j++) {
                        int32_t z = buf[i] + data[k++];
                        switch_normalize_to_16bit(z);
                        buf[i] = (int16_t) z;
                }
        }

        memcpy(data, buf, len);
        free(buf);

}

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

Definition at line 256 of file switch_resample.c.

{
        int i;
        int32_t x;

        if (samples > other_samples) {
                x = other_samples;
        } else {
                x = samples;
        }

        for (i = 0; i < x; i++) {
                data[i] -= other_data[i];
        }

        return x;
}

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