Audio Resample Functions

Collaboration diagram for Audio Resample Functions:

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

Macros
#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. 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...

Detailed Description

Macro Definition Documentation

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

Definition at line 88 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

void switch_change_sln_volume	(	int16_t *	data,
		uint32_t	samples,
		int32_t	vol
	)

Change the volume of a signed linear audio frame.

Parameters

data	the audio data
samples	the number of 2 byte samples
vol	the volume factor -4 -> 4

Definition at line 365 of file switch_resample.c.

References switch_assert, switch_normalize_to_16bit, and switch_normalize_volume.

Referenced by session_audio_callback(), and switch_ivr_play_file().

{
        double newrate = 0;
        double pos[4] = {1.3, 2.3, 3.3, 4.3};
        double neg[4] = {.80, .60, .40, .20};
        double *chart;
        uint32_t i;

        if (vol == 0) return;

        switch_normalize_volume(vol);

        if (vol > 0) {
                chart = pos;
        } else {
                chart = neg;
        }
        
        i = abs(vol) - 1;
        
        switch_assert(i < 4);

        newrate = chart[i];

        if (newrate) {
                int32_t tmp;
                uint32_t x;
                int16_t *fp = data;

                for (x = 0; x < samples; x++) {
                        tmp = (int32_t) (fp[x] * newrate);
                        switch_normalize_to_16bit(tmp);
                        fp[x] = (int16_t) tmp;
                }
        }
}

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.

Parameters

data	the audio data
samples	the number of 2 byte samples
vol	the volume factor -12 -> 12

Definition at line 326 of file switch_resample.c.

References memset(), switch_assert, switch_normalize_to_16bit, and switch_normalize_volume_granular.

{
        double newrate = 0;
        double pos[13] = {1.25, 1.50, 1.75, 2.0, 2.25, 2.50, 2.75, 3.0, 3.25, 3.50, 3.75, 4.0, 4.5};
        double neg[13] = {.917, .834, .751, .668, .585, .502, .419, .336, .253, .087, .017, .004, 0.0};
        double *chart;
        uint32_t i;

        if (vol == 0) return;

        switch_normalize_volume_granular(vol);

        if (vol > 0) {
                chart = pos;
        } else {
                chart = neg;
        }
        
        i = abs(vol) - 1;
        
        switch_assert(i < 13);

        newrate = chart[i];

        if (newrate) {
                int32_t tmp;
                uint32_t x;
                int16_t *fp = data;

                for (x = 0; x < samples; x++) {
                        tmp = (int32_t) (fp[x] * newrate);
                        switch_normalize_to_16bit(tmp);
                        fp[x] = (int16_t) tmp;
                }
        } else {
                memset(data, 0, samples * 2);
        }
}

int switch_char_to_float	(	char *	c,
		float *	f,
		int	len
	)

Convert an array of chars to an array of floats.

Parameters

c	the char buffer
f	the float buffer
len	the length of the buffers

Returns

the size of the converted buffer

Definition at line 140 of file switch_resample.c.

References MAXSAMPLE, and NORMFACT.

{
        int i;

        if (len % 2) {
                return (-1);
        }

        for (i = 1; i < len; i += 2) {
                f[(int) (i / 2)] = (float) (((c[i]) * 0x100) + c[i - 1]);
                f[(int) (i / 2)] /= NORMFACT;
                if (f[(int) (i / 2)] > MAXSAMPLE)
                        f[(int) (i / 2)] = MAXSAMPLE;
                if (f[(int) (i / 2)] < -MAXSAMPLE)
                        f[(int) (i / 2)] = -MAXSAMPLE;
        }
        return len / 2;
}

int switch_float_to_char	(	float *	f,
		char *	c,
		int	len
	)

Convert an array of floats to an array of chars.

Parameters

f	an array of floats
c	an array of chars
len	the length of the buffers

Returns

the size of the converted buffer

Definition at line 159 of file switch_resample.c.

References NORMFACT.

{
        int i;
        float ft;
        long l;
        for (i = 0; i < len; i++) {
                ft = f[i] * NORMFACT;
                if (ft >= 0) {
                        l = (long) (ft + 0.5);
                } else {
                        l = (long) (ft - 0.5);
                }
                c[i * 2] = (unsigned char) ((l) & 0xff);
                c[i * 2 + 1] = (unsigned char) (((l) >> 8) & 0xff);
        }
        return len * 2;
}

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.

Parameters

f	the float buffer
s	the short buffer
len	the length of the buffers

Returns

the size of the converted buffer

Definition at line 121 of file switch_resample.c.

References MAXSAMPLE, and NORMFACT.

{
        switch_size_t i;
        float ft;
        for (i = 0; i < len; i++) {
                ft = f[i] * NORMFACT;
                if (ft >= 0) {
                        s[i] = (short) (ft + 0.5);
                } else {
                        s[i] = (short) (ft - 0.5);
                }
                if ((float) s[i] > MAXSAMPLE)
                        s[i] = (short) MAXSAMPLE / 2;
                if (s[i] < (short) -MAXSAMPLE)
                        s[i] = (short) -MAXSAMPLE / 2;
        }
        return len;
}

void switch_generate_sln_silence	(	int16_t *	data,
		uint32_t	samples,
		uint32_t	channels,
		uint32_t	divisor
	)

Generate static noise.

Parameters

data	the audio data buffer
samples	the number of 2 byte samples
divisor	the volume factor

Definition at line 198 of file switch_resample.c.

References memset(), and switch_micro_time_now().

Referenced by audio_bridge_thread(), session_audio_callback(), switch_ivr_collect_digits_count(), switch_ivr_originate(), switch_ivr_park(), switch_ivr_record_file(), switch_ivr_sleep(), and switch_ivr_wait_for_answer().

{
        int16_t s;
        uint32_t x, i, j;
        int sum_rnd = 0;
        int16_t rnd2 = (int16_t) switch_micro_time_now() + (int16_t) (intptr_t) data;

        if (channels == 0) channels = 1;

        assert(divisor);

        if (divisor == (uint32_t)-1) {
                memset(data, 0, samples * 2);
                return;
        }

        for (i = 0; i < samples; i++, sum_rnd = 0) {
                for (x = 0; x < 6; x++) {
                        rnd2 = rnd2 * 31821U + 13849U;
                        sum_rnd += rnd2;
                }

                s = (int16_t) ((int16_t) sum_rnd / (int) divisor);              

                for (j = 0; j < channels; j++) {
                        *data = s;
                        data++;                 
                }


        }
}

void switch_resample_destroy

(

switch_audio_resampler_t **

resampler

)

Destroy an existing resampler handle.

Parameters

resampler

the resampler handle to destroy

Definition at line 108 of file switch_resample.c.

Referenced by switch_core_asr_close(), switch_core_file_close(), switch_core_media_set_codec(), switch_core_session_read_frame(), switch_core_session_reset(), switch_core_session_write_frame(), and switch_core_speech_close().

{

        if (resampler && *resampler) {
                if ((*resampler)->resampler) {
                        speex_resampler_destroy((*resampler)->resampler);
                }
                free((*resampler)->to);
                free(*resampler);
                *resampler = NULL;
        }
}

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.

Parameters

new_resampler	NULL pointer to aim at the new handle
from_rate	the rate to transfer from in hz
to_rate	the rate to transfer to in hz
quality	the quality desired

Returns

SWITCH_STATUS_SUCCESS if the handle was created

Definition at line 55 of file switch_resample.c.

References switch_audio_resampler_t::channels, switch_audio_resampler_t::factor, switch_audio_resampler_t::from_rate, switch_audio_resampler_t::resampler, switch_audio_resampler_t::rfactor, switch_assert, switch_resample_calc_buffer_size, SWITCH_STATUS_GENERR, SWITCH_STATUS_SUCCESS, switch_zmalloc, switch_audio_resampler_t::to, switch_audio_resampler_t::to_rate, and switch_audio_resampler_t::to_size.

{
        int err = 0;
        switch_audio_resampler_t *resampler;
        double lto_rate, lfrom_rate;

        switch_zmalloc(resampler, sizeof(*resampler));

        if (!channels) channels = 1;
        
        resampler->resampler = speex_resampler_init(channels, from_rate, to_rate, quality, &err);

        if (!resampler->resampler) {
                free(resampler);
                return SWITCH_STATUS_GENERR;
        }

        *new_resampler = resampler;
        lto_rate = (double) resampler->to_rate;
        lfrom_rate = (double) resampler->from_rate;
        resampler->from_rate = from_rate;
        resampler->to_rate = to_rate;
        resampler->factor = (lto_rate / lfrom_rate);
        resampler->rfactor = (lfrom_rate / lto_rate);
        resampler->channels = channels;
        
        //resampler->to_size = resample_buffer(to_rate, from_rate, (uint32_t) to_size);

        resampler->to_size = switch_resample_calc_buffer_size(resampler->to_rate, resampler->from_rate, to_size) / 2;
        resampler->to = malloc(resampler->to_size * sizeof(int16_t) * resampler->channels);
        switch_assert(resampler->to);

        return SWITCH_STATUS_SUCCESS;
}

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.

Parameters

resampler	the resample handle
src	the source data
srclen	the length of the source data

Returns

the used size of dst

Definition at line 93 of file switch_resample.c.

References switch_assert, and switch_resample_calc_buffer_size.

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().

{
        int to_size = switch_resample_calc_buffer_size(resampler->to_rate, resampler->from_rate, srclen) / 2;

        if (to_size > resampler->to_size) {
                resampler->to_size = to_size;
                resampler->to = realloc(resampler->to, resampler->to_size * sizeof(int16_t) * resampler->channels);
                switch_assert(resampler->to);
        }
        
        resampler->to_len = resampler->to_size;
        speex_resampler_process_interleaved_int(resampler->resampler, src, &srclen, resampler->to, &resampler->to_len);
        return resampler->to_len;
}

int switch_short_to_float	(	short *	s,
		float *	f,
		int	len
	)

Convert an array of shorts to an array of floats.

Parameters

s	an array of shorts
f	an array of floats
len	the size of the buffers

Returns

the size of the converted buffer

Definition at line 177 of file switch_resample.c.

References NORMFACT.

{
        int i;

        for (i = 0; i < len; i++) {
                f[i] = (float) (s[i]) / NORMFACT;
                /* f[i] = (float) s[i]; */
        }
        return len;
}

void switch_swap_linear	(	int16_t *	buf,
		int	len
	)

Perform a byteswap on a buffer of 16 bit samples.

Parameters

buf	an array of samples
len	the size of the array

Definition at line 189 of file switch_resample.c.

Referenced by read_rtp_packet(), rtp_common_write(), and switch_ivr_play_file().

{
        int i;
        for (i = 0; i < len; i++) {
                buf[i] = ((buf[i] >> 8) & 0x00ff) | ((buf[i] << 8) & 0xff00);
        }
}