Function iffts1

src/core/_SoundPipe_FFT.cpp:2605–2653

#if 0
static void iffts1(SPFLOAT * ioptr, int M, SPFLOAT * Utbl, int16_t * BRLow)
{
    /* Compute in-place inverse complex fft on the rows of the input array  */
    /* INPUTS                                                               */
    /*   *ioptr = input data array                                          */
    /*   M = log2 of fft size                                               */
    /*   *Utbl = cosine table                                               */
    /*   *BRLow = bit reversed counter table                                */
    /* OUTPUTS                                                              */
    /*   *ioptr = output data array                                         */

    int StageCnt;
    int NDiffU;
    const SPFLOAT scale = 1.0 / POW2(M);

    switch (M)
    {
        case 0:
            break;
        case 1:
            ifft2pt(ioptr, scale); /* a 2 pt fft */
            break;
        case 2:
            ifft4pt(ioptr, scale); /* a 4 pt fft */
            break;
        case 3:
            ifft8pt(ioptr, scale); /* an 8 pt fft */
            break;
        default:
            /* bit reverse and first radix 2 stage */
            scbitrevR2(ioptr, M, BRLow, scale);
            StageCnt = (M - 1) / 3; /* number of radix 8 stages */
            NDiffU = 2; /* one radix 2 stage already complete */
            if ((M - 1 - (StageCnt * 3)) == 1)
            {
                ibfR2(ioptr, M, NDiffU); /* 1 radix 2 stage */
                NDiffU *= 2;
            }
            if ((M - 1 - (StageCnt * 3)) == 2)
            {
                ibfR4(ioptr, M, NDiffU); /* 1 radix 4 stage */
                NDiffU *= 4;
            }
            if (M <= (int) MCACHE)
                ibfstages(ioptr, M, Utbl, 1, NDiffU, StageCnt); /* RADIX 8 Stages */
            else
                ifftrecurs(ioptr, M, Utbl, 1, NDiffU, StageCnt); /* RADIX 8 Stages */
    }
}
#endif

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