libsent/src/adin/ds48to16.c File Reference

Down sampling from 48kHz to 16kHz. More...

#include <sent/stddefs.h>
#include <sent/adin.h>
#include "lpfcoef_3to4.h"
#include "lpfcoef_2to1.h"

Go to the source code of this file.

Defines
#define	USE_HEADER_COEF
	TRUE if use embedded values on header.
#define	mod(x)   ((x) & (DS_RBSIZE -1))
	USB device sampling rate.
Functions
static void	load_filter_from_header_2to1 (DS_FILTER *f)
	Set 1/2 filter coefficients from header values.
static void	load_filter_from_header_3to4 (DS_FILTER *f)
	Set 4/2 filter coefficients from header values.
static void	init_filter (DS_FILTER *f, int d, int u)
	Initialize filter values.
static void	firin (DS_FILTER *f, double in)
	Store input for FIR filter.
static double	firout (DS_FILTER *f, int os)
	Get filtered output from FIR filter.
static int	do_filter (DS_FILTER *f, double *dst, double *src, int len, int maxlen)
	Perform down sampling of input samples.
DS_BUFFER *	ds48to16_new ()
	Setup for down sampling.
void	ds48to16_free (DS_BUFFER *ds)
	Free the down sampling buffer.
int	ds48to16 (SP16 *dst, SP16 *src, int srclen, int maxdstlen, DS_BUFFER *ds)
	Perform down sampling of input samples to 1/3.

---

Detailed Description

Down sampling from 48kHz to 16kHz.

Author:

Akinobu LEE

Date:

Sun Feb 13 16:18:26 2005

Revision

1.1.1.1

Definition in file ds48to16.c.

---

Define Documentation

#define mod

(

x

)

((x) & (DS_RBSIZE -1))

USB device sampling rate.

filter parameters in header Buffer index cycler

Definition at line 41 of file ds48to16.c.

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Function Documentation

static void load_filter_from_header_2to1

(

DS_FILTER *

f

)

[static]

Set 1/2 filter coefficients from header values.

Parameters:

f

[out] filter info

Definition at line 51 of file ds48to16.c.

static void load_filter_from_header_3to4

(

DS_FILTER *

f

)

[static]

Set 4/2 filter coefficients from header values.

Parameters:

f

[out] filter info

Definition at line 69 of file ds48to16.c.

static void init_filter	(	DS_FILTER *	f,
		int	d,
		int	u
	)			[static]

Initialize filter values.

Parameters:

	f	[i/o] filter info
	u	[in] up sampling rate
	d	[in] down sampling rate

Definition at line 123 of file ds48to16.c.

static void firin	(	DS_FILTER *	f,
		double	in
	)			[static]

Store input for FIR filter.

Parameters:

	f	[i/o] filter info
	in	[in] an input sample

Definition at line 150 of file ds48to16.c.

static double firout	(	DS_FILTER *	f,
		int	os
	)			[static]

Get filtered output from FIR filter.

Parameters:

	f	[i/o] filter info
	os	[in] point

Returns:

output value

Definition at line 165 of file ds48to16.c.

static int do_filter	(	DS_FILTER *	f,
		double *	dst,
		double *	src,
		int	len,
		int	maxlen
	)			[static]

Perform down sampling of input samples.

Parameters:

	f	[i/o] filter info
	dst	[out] store the resulting samples
	src	[in] input samples
	len	[in] number of input samples
	maxlen	[in] maximum length of dst

Returns:

the number of samples written to dst, or -1 on errror.

Definition at line 190 of file ds48to16.c.

DS_BUFFER* ds48to16_new

(

)

Setup for down sampling.

Returns:

newly allocated buffer for down sampling

Definition at line 267 of file ds48to16.c.

Referenced by adin_setup_all().

void ds48to16_free

(

DS_BUFFER *

ds

)

Free the down sampling buffer.

Parameters:

ds

[i/o] down sampling buffer to free

Definition at line 304 of file ds48to16.c.

int ds48to16	(	SP16 *	dst,
		SP16 *	src,
		int	srclen,
		int	maxdstlen,
		DS_BUFFER *	ds
	)

Perform down sampling of input samples to 1/3.

Parameters:

	dst	[out] store the resulting samples
	src	[in] input samples
	srclen	[in] number of input samples
	maxdstlen	[in] maximum length of dst
	ds	[i/o] down sampling buffer

Returns:

the number of samples written to dst, or -1 on errror.

Definition at line 329 of file ds48to16.c.

Referenced by adin_cut().

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