annotate vamp-sdk/FFT.h @ 446:d132b92ec65d vampipe

Add FFTComplex class by analogy to FFTReal

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

/*
    Vamp

    An API for audio analysis and feature extraction plugins.

    Centre for Digital Music, Queen Mary, University of London.
    Copyright 2006-2012 Chris Cannam and QMUL.
  
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*/

#ifndef _VAMP_FFT_H_
#define _VAMP_FFT_H_

#include "plugguard.h"
_VAMP_SDK_PLUGSPACE_BEGIN(FFT.h)

namespace Vamp {

/**
 * A simple FFT implementation provided for convenience of plugin
 * authors. This class provides one-shot (i.e. fixed table state is
 * recalculated every time) double-precision complex-complex
 * transforms. For repeated transforms from real time-domain data, use
 * an FFTComplex or FFTReal object instead.
 *
 * Note: If the SDK has been compiled with the SINGLE_PRECISION_FFT
 * flag, then all FFTs will use single precision internally. The
 * default is double precision. The API uses doubles in either case.
 *
 * The forward transform is unscaled; the inverse transform is scaled
 * by 1/n.
 */
class FFT
{
public:
    /**
     * Calculate a one-shot forward transform of size n.
     * n must be a multiple of 2.
     *
     * ri and ii must point to the real and imaginary component arrays
     * of the input. For real input, ii may be NULL.
     *
     * ro and io must point to enough space to receive the real and
     * imaginary component arrays of the output.
     *
     * All input and output arrays are of size n.
     */
    static void forward(unsigned int n,
                        const double *ri, const double *ii,
                        double *ro, double *io);

    /**
     * Calculate a one-shot inverse transform of size n.
     * n must be a power of 2, greater than 1.
     *
     * ri and ii must point to the real and imaginary component arrays
     * of the input. For real input, ii may be NULL.
     *
     * ro and io must point to enough space to receive the real and
     * imaginary component arrays of the output. The output is scaled
     * by 1/n. The output pointers may not be NULL, even if the output
     * is expected to be real.
     *
     * All input and output arrays are of size n.
     */
    static void inverse(unsigned int n,
                        const double *ri, const double *ii,
                        double *ro, double *io);
};

/**
 * A simple FFT implementation provided for convenience of plugin
 * authors. This class provides double-precision complex-complex
 * transforms.
 *
 * Note: If the SDK has been compiled with the SINGLE_PRECISION_FFT
 * flag, then all FFTs will use single precision internally. The
 * default is double precision. The API uses doubles in either case.
 *
 * The forward transform is unscaled; the inverse transform is scaled
 * by 1/n.
 */
class FFTComplex
{
    /**
     * Prepare to calculate transforms of size n.
     * n must be a multiple of 2.
     */
    FFTComplex(unsigned int n);

    ~FFTComplex();

    /**
     * Calculate a forward transform of size n.
     *
     * ci must point to the interleaved complex input data of size n
     * (that is, 2n doubles in total).
     *
     * co must point to enough space to receive an interleaved complex
     * output array of size n (that is, 2n doubles in total).
     */
    void forward(const double *ci, double *co);

    /**
     * Calculate an inverse transform of size n.
     *
     * ci must point to an interleaved complex input array of size n
     * (that is, 2n doubles in total).
     *
     * co must point to enough space to receive the interleaved
     * complex output data of size n (that is, 2n doubles in
     * total). The output is scaled by 1/n.
     */
    void inverse(const double *ci, double *co);

private:
    class D;
    D *m_d;
};

/**
 * A simple FFT implementation provided for convenience of plugin
 * authors. This class provides transforms between double-precision
 * real time-domain and double-precision complex frequency-domain
 * data.
 *
 * Note: If the SDK has been compiled with the SINGLE_PRECISION_FFT
 * flag, then all FFTs will use single precision internally. The
 * default is double precision. The API uses doubles in either case.
 *
 * The forward transform is unscaled; the inverse transform is scaled
 * by 1/n.
 */
class FFTReal
{
    /**
     * Prepare to calculate transforms of size n.
     * n must be a multiple of 2.
     */
    FFTReal(unsigned int n);

    ~FFTReal();

    /**
     * Calculate a forward transform of size n.
     *
     * ri must point to the real input data of size n.
     *
     * co must point to enough space to receive an interleaved complex
     * output array of size n/2+1 (that is, n+2 doubles in total).
     */
    void forward(const double *ri, double *co);

    /**
     * Calculate an inverse transform of size n.
     *
     * ci must point to an interleaved complex input array of size
     * n/2+1 (that is, n+2 doubles in total).
     *
     * ro must point to enough space to receive the real output data
     * of size n. The output is scaled by 1/n and only the real part
     * is returned.
     */
    void inverse(const double *ci, double *ro);

private:
    class D;
    D *m_d;
};

}

_VAMP_SDK_PLUGSPACE_END(FFT.h)

#endif