# OpenCV Fourier Transform complex output issue

I try to do some Fourier analysis, but in the OpenCV `cv::dft`

function the `cv::DFT_COMPLEX_OUTPUT`

seems not working. I do the following:

```
// Calculate Fourier transform for each time signal
cv::Mat hf, hf_raw, h, h_raw;
cv::Mat Fp(Pt.size[0], Pt.size[1], CV_64FC2);
cv::Mat Fz(Pt.size[0], Pt.size[1], CV_64FC2);
cv::dft(Pt.t(), Fp, cv::DFT_ROWS, cv::DFT_COMPLEX_OUTPUT);
cv::dft(Zt.t(), Fz, cv::DFT_ROWS, cv::DFT_COMPLEX_OUTPUT);
// [DEBUG]
// Fp and Fz has to be (K*4 x WINDOW_LENGTH) size in the current case (24 x 256)
std::cout << "Fp.size: " << Fp.size << std::endl;
// -> OK
// Fp elements should be complx
std::cout << "Fp.type(): " << Fp.type() << std::endl;
// -> Lots of zero at the end!!! -> With cv::DFT_REAL_OUTPUT there are no zeros
cv::Mat nom, denom, W;
cv::mulSpectrums(Fp, Fp, nom, cv::DFT_ROWS, true);
cv::mulSpectrums(Fz, Fz, denom, cv::DFT_ROWS, true);
```

I declare `Fp`

and `Fz`

to be two channeled in order to hold the real and complex values (on which the `cv::mulSpectrums`

function can operate). But `Fp.type()`

results in `6`

which means the type of the output matrix is `CV_64FC1`

.