void DC_block( float * data, long Nsamples )
{
    float *p;
    long count;
    float facc = 0.0f;

    long ofs = SEARCHBUFFER * Downsample;

    p = data + ofs;
    for( count = (Nsamples - 2 * ofs); count > 0L; count-- )
        facc += *(p++);
    facc /= Nsamples;

    p = data + ofs;
    for( count = (Nsamples - 2 * ofs); count > 0L; count-- )
        *(p++) -= facc;

    p = data + ofs;
    for( count = 0L; count < Downsample; count++ )
       *(p++) *= (0.5f + count) / Downsample;

    p = data + Nsamples - ofs - 1L;
    for( count = 0L; count < Downsample; count++ )
       *(p--) *= (0.5f + count) / Downsample;
}

void FFTInit(unsigned long N)
{
    unsigned long   C, L, K;
    float           Theta;
    float         * PFFTPhi;
    
    if( (FFTSwapInitialised != N) && (FFTSwapInitialised != 0) )
        FFTFree();

    if( FFTSwapInitialised == N )
    {
        return;
    }
    else
    {
        C = N;
        for( FFTLog2N = 0; C > 1; C >>= 1 )
            FFTLog2N++;

        C = 1;
        C <<= FFTLog2N;
        if( N == C )
            FFTSwapInitialised = N;

        FFTButter = (unsigned long *) safe_malloc( sizeof(unsigned long) * (N >> 1) );
        FFTBitSwap = (unsigned long *) safe_malloc( sizeof(unsigned long) * N );
        FFTPhi = (float *) safe_malloc( 2 * sizeof(float) * (N >> 1) );
    
        PFFTPhi = FFTPhi;
        for( C = 0; C < (N >> 1); C++ )
        {
            Theta = (TWOPI * C) / N;
            (*(PFFTPhi++)) = (float) cos( Theta );
            (*(PFFTPhi++)) = (float) sin( Theta );
        }
    
        FFTButter[0] = 0;
        L = 1;
        K = N >> 2;
        while( K >= 1 )
        {
            for( C = 0; C < L; C++ )
                FFTButter[C+L] = FFTButter[C] + K;
            L <<= 1;
            K >>= 1;
        }
    }
}

void apply_filters( float * data, long Nsamples )
{
    IIRFilt( InIIR_Hsos, InIIR_Nsos, NULL,
             data, Nsamples + DATAPADDING_MSECS  * (Fs / 1000), NULL );
}