window.h

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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
#ifndef SP_WINDOW_H
#define SP_WINDOW_H
 
namespace sp
{
 
arma_inline arma::vec cos_win( const arma::uword N, const arma::vec& a )
{
    arma::vec h( N );
    for( arma::uword i = 0; i < N; i++ )
    {
        h[i] = a[0] - a[1] * std::cos( 1.0 * PI_2 * i / ( N - 1 ) ) + a[2] * std::cos( 2.0 * PI_2 * i / ( N - 1 ) ) - a[3] * std::cos( 3.0 * PI_2 * i / ( N - 1 ) )
               + a[4] * std::cos( 4.0 * PI_2 * i / ( N - 1 ) );
    }
    return h;
}
 
arma_inline arma::vec hamming( const arma::uword N )
{
    arma::vec a = arma::zeros<arma::vec>( 5 );
    a[0]        = 0.54;
    a[1]        = 0.46;
    return cos_win( N, a );
}
 
arma_inline arma::vec hann( const arma::uword N )
{
    arma::vec a = arma::zeros<arma::vec>( 5 );
    a[0]        = 0.5;
    a[1]        = 0.5;
    return cos_win( N, a );
}
 
arma_inline arma::vec blackman( const arma::uword N )
{
    arma::vec a = arma::zeros<arma::vec>( 5 );
    a[0]        = 0.42; // 7938/18608.0
    a[1]        = 0.5;  // 9240/18608.0
    a[2]        = 0.08; // 1430/18608.0
    return cos_win( N, a );
}
 
arma_inline arma::vec blackmanharris( const arma::uword N )
{
    arma::vec a = arma::zeros<arma::vec>( 5 );
    a[0]        = 0.35875;
    a[1]        = 0.48829;
    a[2]        = 0.14128;
    a[3]        = 0.01168;
    return cos_win( N, a );
}
 
arma_inline arma::vec flattopwin( const arma::uword N )
{
    arma::vec a = arma::zeros<arma::vec>( 5 );
    a[0]        = 0.21557895;
    a[1]        = 0.41663158;
    a[2]        = 0.277263158;
    a[3]        = 0.083578947;
    a[4]        = 0.006947368;
    return cos_win( N, a );
}
 
arma_inline arma::vec hanning( const arma::uword N )
{
    arma::vec h( N );
    for( arma::uword i = 0; i < N; i++ )
    {
        h[i] = 0.5 - 0.5 * std::cos( PI_2 * ( i + 1 ) / ( N + 1 ) );
    }
    return h;
}
 
arma_inline arma::vec kaiser( const arma::uword N, double beta )
{
    arma::vec h( N );
    double    bb = besseli0( beta );
    for( arma::uword i = 0; i < N; i++ )
    {
        h[i] = besseli0( beta * sqrt( 4.0 * i * ( N - 1 - i ) ) / ( N - 1 ) ) / bb;
    }
    return h;
}
 
arma_inline arma::vec triang( const arma::uword N )
{
    arma::vec h( N );
    if( N % 2 ) // Odd
    {
        for( arma::uword i = 0; i < ( N - 1 ) / 2; i++ )
        {
            h[i]         = 2.0 * ( i + 1 ) / ( N + 1 );
            h[N - i - 1] = h[i];
        }
        h[( N - 1 ) / 2] = 1.0;
    }
    else // Even
    {
        for( arma::uword i = 0; i < N / 2; i++ )
        {
            h[i]         = ( 2.0 * i + 1 ) / N;
            h[N - i - 1] = h[i];
        }
    }
    return h;
}
 
} // namespace sp
#endif