librubberband/src/dsp/MovingMedian.h

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Rubber Band
    An audio time-stretching and pitch-shifting library.
    Copyright 2007-2011 Chris Cannam.
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef _MOVING_MEDIAN_H_
#define _MOVING_MEDIAN_H_

#include "SampleFilter.h"

#include "system/Allocators.h"

#include <algorithm>

namespace RubberBand
{

template <typename T>
class MovingMedian : public SampleFilter<T>
{
    typedef SampleFilter<T> P;

public:
    MovingMedian(int size, float percentile = 50.f) :
        SampleFilter<T>(size),
	m_frame(allocate_and_zero<T>(size)),
	m_sorted(allocate_and_zero<T>(size)),
	m_sortend(m_sorted + P::m_size - 1) {
        setPercentile(percentile);
    }

    ~MovingMedian() { 
	deallocate(m_frame);
	deallocate(m_sorted);
    }

    void setPercentile(float p) {
        m_index = int((P::m_size * p) / 100.f);
        if (m_index >= P::m_size) m_index = P::m_size-1;
        if (m_index < 0) m_index = 0;
    }

    void push(T value) {
	drop(m_frame[0]);
	v_move(m_frame, m_frame+1, P::m_size-1);
	m_frame[P::m_size-1] = value;
	put(value);
    }

    T get() const {
	return m_sorted[m_index];
    }

    void reset() {
	v_zero(m_frame, P::m_size);
	v_zero(m_sorted, P::m_size);
    }

private:
    T *const m_frame;
    T *const m_sorted;
    T *const m_sortend;
    int m_index;

    void put(T value) {
	// precondition: m_sorted contains m_size-1 values, packed at start
	// postcondition: m_sorted contains m_size values, one of which is value
	T *index = std::lower_bound(m_sorted, m_sortend, value);
	v_move(index + 1, index, m_sortend - index);
	*index = value;
    }

    void drop(T value) {
	// precondition: m_sorted contains m_size values, one of which is value
	// postcondition: m_sorted contains m_size-1 values, packed at start
	T *index = std::lower_bound(m_sorted, m_sortend + 1, value);
	assert(*index == value);
	v_move(index, index + 1, m_sortend - index);
	*m_sortend = T(0);
    }
};

}

#endif