librubberband/src/dsp/SincWindow.h

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

/*
    Rubber Band Library
    An audio time-stretching and pitch-shifting library.
    Copyright 2007-2014 Particular Programs Ltd.

    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.

    Alternatively, if you have a valid commercial licence for the
    Rubber Band Library obtained by agreement with the copyright
    holders, you may redistribute and/or modify it under the terms
    described in that licence.

    If you wish to distribute code using the Rubber Band Library
    under terms other than those of the GNU General Public License,
    you must obtain a valid commercial licence before doing so.
*/

#ifndef _RUBBERBAND_SINC_WINDOW_H_
#define _RUBBERBAND_SINC_WINDOW_H_

#include <cmath>
#include <iostream>
#include <cstdlib>
#include <map>

#include "system/sysutils.h"
#include "system/VectorOps.h"
#include "system/Allocators.h"

namespace RubberBand {

template <typename T>
class SincWindow
{
public:
    /**
     * Construct a sinc windower which produces a window of size n
     * containing the values of sinc(x) with x=0 at index n/2, such
     * that the distance from -pi to pi (the point at which the sinc
     * function first crosses zero, for negative and positive
     * arguments respectively) is p samples.
     */
    SincWindow(int n, int p) : m_size(n), m_p(p), m_cache(0) {
        encache();
    }
    SincWindow(const SincWindow &w) : m_size(w.m_size), m_p(w.m_p), m_cache(0) {
        encache();
    }
    SincWindow &operator=(const SincWindow &w) {
	if (&w == this) return *this;
	m_size = w.m_size;
	m_p = w.m_p;
        m_cache = 0;
	encache();
	return *this;
    }
    virtual ~SincWindow() {
        deallocate(m_cache);
    }

    /**
     * Regenerate the sinc window with the same size, but a new scale
     * (the p value is interpreted as for the argument of the same
     * name to the constructor).  If p is unchanged from the previous
     * value, do nothing (quickly).
     */
    inline void rewrite(int p) {
        if (m_p == p) return;
        m_p = p;
        encache();
    }
    
    inline void cut(T *const R__ dst) const {
        v_multiply(dst, m_cache, m_size);
    }

    inline void cut(const T *const R__ src, T *const R__ dst) const {
        v_multiply(dst, src, m_cache, m_size);
    }

    inline void add(T *const R__ dst, T scale) const {
        v_add_with_gain(dst, m_cache, m_size, scale);
    }

    inline T getArea() const { return m_area; }
    inline T getValue(int i) const { return m_cache[i]; }

    inline int getSize() const { return m_size; }
    inline int getP() const { return m_p; }

    /**
     * Write a sinc window of size n with scale p (the p value is
     * interpreted as for the argument of the same name to the
     * constructor).
     */
    static
    void write(T *const R__ dst, const int n, const int p) {
        const int half = n/2;
        writeHalf(dst, n, p);
        int target = half - 1;
        for (int i = half + 1; i < n; ++i) {
            dst[target--] = dst[i];
        }
        const T twopi = 2. * M_PI;
        T arg = T(half) * twopi / p;
        dst[0] = sin(arg) / arg;
    }

protected:
    int m_size;
    int m_p;
    T *R__ m_cache;
    T m_area;

    /**
     * Write the positive half (i.e. n/2 to n-1) of a sinc window of
     * size n with scale p (the p value is interpreted as for the
     * argument of the same name to the constructor). The negative
     * half (indices 0 to n/2-1) of dst is left unchanged.
     */
    static
    void writeHalf(T *const R__ dst, const int n, const int p) {
        const int half = n/2;
        const T twopi = 2. * M_PI;
        dst[half] = T(1.0);
        for (int i = 1; i < half; ++i) {
            T arg = T(i) * twopi / p;
            dst[half+i] = sin(arg) / arg;
        }
    }
    
    void encache() {
        if (!m_cache) {
            m_cache = allocate<T>(m_size);
        }

        write(m_cache, m_size, m_p);
	
        m_area = 0;
        for (int i = 0; i < m_size; ++i) {
            m_area += m_cache[i];
        }
        m_area /= m_size;
    }
};

}

#endif