ed9e0fa975
Median filter has an advantage over moving average that it is much less sensitive to outliers. For instance, it allows much faster recovery from an external clock time step which happened between receiving sync message and sending delay_req message. The measured delay includes a large error, but the median is still a good estimate of the delay and the first step correction applied by the servo is right. In this implementation the median update has linear time complexity. Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
65 lines
1.8 KiB
C
65 lines
1.8 KiB
C
/**
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* @file filter.h
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* @brief Implements a generic filter interface.
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* @note Copyright (C) 2013 Miroslav Lichvar <mlichvar@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef HAVE_FILTER_H
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#define HAVE_FILTER_H
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#include "tmv.h"
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/** Opaque type */
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struct filter;
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/**
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* Defines the available filters.
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*/
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enum filter_type {
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FILTER_MOVING_AVERAGE,
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FILTER_MOVING_MEDIAN,
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};
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/**
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* Create a new instance of a filter.
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* @param type The type of the filter to create.
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* @param length The filter's length.
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* @return A pointer to a new filter on success, NULL otherwise.
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*/
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struct filter *filter_create(enum filter_type type, int length);
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/**
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* Destroy an instance of a filter.
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* @param filter Pointer to a filter obtained via @ref filter_create().
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*/
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void filter_destroy(struct filter *filter);
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/**
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* Feed a sample into a filter.
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* @param filter Pointer to a filter obtained via @ref filter_create().
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* @param sample The input sample.
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* @return The output value.
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*/
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tmv_t filter_sample(struct filter *filter, tmv_t sample);
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/**
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* Reset a filter.
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* @param filter Pointer to a filter obtained via @ref filter_create().
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*/
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void filter_reset(struct filter *filter);
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#endif
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