1e_filter.h File Reference

Implementation of the 1 euro filter. More...

#include "std.h"
#include <math.h>

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Data Structures
struct	OneEuroLPFilter
	simple low pass filter. More...
struct	OneEuroFilter
	configuration parameters. More...

Functions
static void	init_1e_filter (struct OneEuroFilter *filter, float rate, float mincutoff, float beta, float dcutoff)
	Initialize a 1 Euro Filter instance. More...
static void	reset_1e_filter (struct OneEuroFilter *filter)
	Reset filter (gains and parameters unchanged) More...
static float	compute_1e_filter_lp (struct OneEuroLPFilter *filter, float x, float alpha)
	Filter a float using the given low-pass filter and the given alpha value. More...
static float	compute_1e_filter_alpha (struct OneEuroFilter *filter, float cutoff)
	Compute Alpha for a given One Euro Filter and a given cutoff frequency. More...
static float	update_1e_filter (struct OneEuroFilter *filter, float x)
	Filter a float using the given One Euro Filter. More...
static float	update_1e_filter_at_time (struct OneEuroFilter *filter, float x, uint32_t timestamp)
	Filter a float using the given One Euro Filter and the given timestamp. More...

Detailed Description

Implementation of the 1 euro filter.

See: http://cristal.univ-lille.fr/~casiez/1euro/

Ref: Casiez, G., Roussel, N. and Vogel, D. (2012). 1€ Filter: A Simple Speed-based Low-pass Filter for Noisy Input in Interactive Systems. Proceedings of the ACM Conference on Human Factors in Computing Systems (CHI '12). Austin, Texas (May 5-12, 2012). New York: ACM Press, pp. 2527-2530.

Definition in file 1e_filter.h.

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Data Structure Documentation

OneEuroLPFilter

struct OneEuroLPFilter

simple low pass filter.

TODO use existing implementation ?

Definition at line 42 of file 1e_filter.h.

Data Fields
bool	first_time
float	hatx
float	hatxprev

OneEuroFilter

struct OneEuroFilter

configuration parameters.

Definition at line 51 of file 1e_filter.h.

Collaboration diagram for OneEuroFilter:

Data Fields
float	beta	cutoff slope
float	dcutoff	derivative cutoff freq (in Hz)
struct OneEuroLPFilter	dxfilt	low pass filter for derivative
bool	first_time	first time flag
uint32_t	last_time	last update time in ms
float	mincutoff	min cutoff freq (in Hz)
float	rate	data update rate (in Hz)
struct OneEuroLPFilter	xfilt	low pass filter

Function Documentation

compute_1e_filter_alpha()

static float compute_1e_filter_alpha ( struct OneEuroFilter *  filter, float  cutoff  )

inlinestatic

Compute Alpha for a given One Euro Filter and a given cutoff frequency.

Definition at line 113 of file 1e_filter.h.

References OneEuroFilter::rate.

Referenced by update_1e_filter().

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compute_1e_filter_lp()

static float compute_1e_filter_lp ( struct OneEuroLPFilter *  filter, float  x, float  alpha  )

inlinestatic

Filter a float using the given low-pass filter and the given alpha value.

Definition at line 99 of file 1e_filter.h.

References alpha, OneEuroLPFilter::first_time, OneEuroLPFilter::hatx, and OneEuroLPFilter::hatxprev.

Referenced by update_1e_filter().

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init_1e_filter()

static void init_1e_filter ( struct OneEuroFilter *  filter, float  rate, float  mincutoff, float  beta, float  dcutoff  )

inlinestatic

Initialize a 1 Euro Filter instance.

Definition at line 65 of file 1e_filter.h.

References OneEuroFilter::beta, OneEuroFilter::dcutoff, OneEuroFilter::dxfilt, OneEuroLPFilter::first_time, OneEuroFilter::first_time, OneEuroLPFilter::hatx, OneEuroLPFilter::hatxprev, OneEuroFilter::last_time, OneEuroFilter::mincutoff, OneEuroFilter::rate, and OneEuroFilter::xfilt.

Referenced by filter_1euro_imu_init().

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reset_1e_filter()

static void reset_1e_filter ( struct OneEuroFilter *  filter )

inlinestatic

Reset filter (gains and parameters unchanged)

Definition at line 84 of file 1e_filter.h.

References OneEuroFilter::dxfilt, OneEuroLPFilter::first_time, OneEuroFilter::first_time, OneEuroLPFilter::hatx, OneEuroLPFilter::hatxprev, OneEuroFilter::last_time, and OneEuroFilter::xfilt.

Referenced by filter_1euro_imu_reset().

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update_1e_filter()

static float update_1e_filter ( struct OneEuroFilter *  filter, float  x  )

inlinestatic

Filter a float using the given One Euro Filter.

Definition at line 124 of file 1e_filter.h.

References OneEuroFilter::beta, compute_1e_filter_alpha(), compute_1e_filter_lp(), OneEuroFilter::dcutoff, OneEuroFilter::dxfilt, OneEuroFilter::first_time, OneEuroLPFilter::hatxprev, OneEuroFilter::mincutoff, OneEuroFilter::rate, and OneEuroFilter::xfilt.

Referenced by accel_cb(), gyro_cb(), and update_1e_filter_at_time().

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update_1e_filter_at_time()

static float update_1e_filter_at_time ( struct OneEuroFilter *  filter, float  x, uint32_t  timestamp  )

inlinestatic

Filter a float using the given One Euro Filter and the given timestamp.

Frequency will be automatically recomputed.

Definition at line 142 of file 1e_filter.h.

References OneEuroFilter::last_time, OneEuroFilter::rate, and update_1e_filter().

Referenced by accel_cb(), and gyro_cb().

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