ossia::one_euro_filter< T > Struct Template Reference

One-euro filter: a low-pass whose cutoff rises with the speed of the signal. More...

Detailed Description

template<typename T = float>
struct ossia::one_euro_filter< T >

One-euro filter: a low-pass whose cutoff rises with the speed of the signal.

Casiez, Roussel and Vogel, "1 euro filter: a simple speed-based low-pass filter for noisy input in interactive systems", CHI 2012.

The point is the jitter/lag tradeoff: at rest the cutoff drops to min_cutoff and the output is very smooth, while a fast movement raises the cutoff so the output stays responsive. Per the authors: if lag during fast motion is the problem, raise beta ; if jitter at rest is the problem, lower min_cutoff.

The derivative is taken against the previous raw input, as in the reference implementation.

Public Types
using	value_type = T

Public Member Functions
OSSIA_INLINE void	reset () noexcept
	Forget the history: the next sample restarts the filter.
OSSIA_INLINE void	assign_parameters (const one_euro_filter &p) noexcept
	Adopt p's tuning, keeping the history.
OSSIA_INLINE T	operator() (T x, T dt) noexcept

Public Attributes
T	min_cutoff {1}
	Cutoff at zero speed, in Hz. Lower is smoother, and laggier.
T	beta {0}
	How much the speed raises the cutoff. 0 degrades to a plain low-pass.
T	d_cutoff {1}
	Cutoff of the low-pass applied to the derivative itself, in Hz.
one_pole_filter< T >	x_filter {}
	Smoother for the value.
one_pole_filter< T >	dx_filter {}
	Smoother for the derivative.
T	x_prev {}
	Previous raw input.

Member Function Documentation

operator()()

template<typename T = float>

OSSIA_INLINE T ossia::one_euro_filter< T >::operator() ( T  x, T  dt  )

inlinenoexcept

Parameters

x	Input sample.
dt	Time since the previous sample, in seconds.

A dt <= 0 returns the previous output unchanged rather than dividing by zero, so that a duplicated timestamp cannot poison the state.