_generate_kernel()

void _generate_kernel	(	kiss_fft_cpx	kernel[],
		kiss_fftr_cfg	cfg,
		enum window_type window_type window_type	,
		float	f,
		float	fmin,
		float	fs,
		int	N )

Definition at line 53 of file cq_kernel.cpp.

                                                                                                                                   {
    // Generates window in the center and zero everywhere else
    float factor = f/fmin;
    int N_window = N/factor; // Scales inversely with frequency (see CQT paper)
    kiss_fft_scalar *time_K = (kiss_fft_scalar*)calloc(N, sizeof(kiss_fft_scalar));
 
    switch(window_type){
        case HAMMING:
            _generate_hamming(&time_K[(N-N_window)/2], N_window);
            break;
        case GAUSSIAN:
            _generate_guassian(&time_K[(N-N_window)/2], N_window);
            break;
    }
 
    // Fills window with f Hz wave sampled at fs Hz
    for(int i = 0; i < N; i++) time_K[i] *= cos(2*M_PI*(f/fs)*(i-N/2));
 
    #ifdef FIXED_POINT // If using fixed point, just scale inversely to N after FFT (don't normalize)
    kiss_fftr(cfg, time_K, kernel); // Outputs garbage for Q31
    for(int i = 0; i < N; i++){
        kernel[i].r *= factor;
        kernel[i].i *= factor;
    }
    #else // Else if floating point, follow CQT paper more exactly (normalize with N before FFT)
    for(int i = 0; i < N; i++) time_K[i] /= N_window;
    kiss_fftr(cfg, time_K, kernel);
    #endif
 
    free(time_K);
}

References _generate_guassian(), _generate_hamming(), GAUSSIAN, HAMMING, kiss_fft_cpx::i, kiss_fft_scalar, kiss_fftr(), M_PI, and kiss_fft_cpx::r.

Referenced by generate_kernels().

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