view src/vamp-sdk/FFTimpl.cpp @ 415:1522e2f6d700

Fix handling of output sample rate in buffering adapter in case where SampleType is Fixed but no sample rate provided (which is invalid behaviour from the plugin, but we might as well do the right thing with it)

/* Public domain FFT implementation from Don Cross. */

static void
fft(unsigned int n, bool inverse,
    const double *ri, const double *ii,
    double *ro, double *io)
{
    if (!ri || !ro || !io) return;

    unsigned int bits;
    unsigned int i, j, k, m;
    unsigned int blockSize, blockEnd;

    double tr, ti;

    if (n < 2) return;
    if (n & (n-1)) return;

    double angle = 2.0 * M_PI;
    if (inverse) angle = -angle;

    for (i = 0; ; ++i) {
	if (n & (1 << i)) {
	    bits = i;
	    break;
	}
    }

#ifdef _MSC_VER
    int *table = (int *)_malloca(n * sizeof(int));
#else
    int table[n];
#endif

    for (i = 0; i < n; ++i) {
        m = i;
        for (j = k = 0; j < bits; ++j) {
            k = (k << 1) | (m & 1);
            m >>= 1;
        }
        table[i] = k;
    }

    if (ii) {
	for (i = 0; i < n; ++i) {
	    ro[table[i]] = ri[i];
	    io[table[i]] = ii[i];
	}
    } else {
	for (i = 0; i < n; ++i) {
	    ro[table[i]] = ri[i];
	    io[table[i]] = 0.0;
	}
    }

    blockEnd = 1;

    for (blockSize = 2; blockSize <= n; blockSize <<= 1) {

	double delta = angle / (double)blockSize;
	double sm2 = -sin(-2 * delta);
	double sm1 = -sin(-delta);
	double cm2 = cos(-2 * delta);
	double cm1 = cos(-delta);
	double w = 2 * cm1;
	double ar[3], ai[3];

	for (i = 0; i < n; i += blockSize) {

	    ar[2] = cm2;
	    ar[1] = cm1;

	    ai[2] = sm2;
	    ai[1] = sm1;

	    for (j = i, m = 0; m < blockEnd; j++, m++) {

		ar[0] = w * ar[1] - ar[2];
		ar[2] = ar[1];
		ar[1] = ar[0];

		ai[0] = w * ai[1] - ai[2];
		ai[2] = ai[1];
		ai[1] = ai[0];

		k = j + blockEnd;
		tr = ar[0] * ro[k] - ai[0] * io[k];
		ti = ar[0] * io[k] + ai[0] * ro[k];

		ro[k] = ro[j] - tr;
		io[k] = io[j] - ti;

		ro[j] += tr;
		io[j] += ti;
	    }
	}

	blockEnd = blockSize;
    }

    if (inverse) {

	double denom = (double)n;

	for (i = 0; i < n; i++) {
	    ro[i] /= denom;
	    io[i] /= denom;
	}
    }

#ifdef _MSC_VER
    _freea(table);
#endif
}