How STFT results in complex signals?

Hey all,

How Short Time Fourier Transform (STFT) results in complex signals that is not direct to work with neural network?

[Walter Roberson]

Why would stft be expected to be restricted to real values?

Stft is just a discrete fourier transform at each step. The result of DFT on a real valued signal is a set of complex coefficients that are skew conjugate symmetric: N real inputs representable in N/2 complex coefficients. That preserves information capacity. In order for the DFT results to be real valued as you seem to think they should be, then the original N points of information would have to be half redundant.

The complex portion of the DFT coefficients encode phase information. Real-life signals almost have some phase information.

[Shining Pearl]

Thankyou Walter for your quick respond,,

Can you please tell me what are the conventional features that are present in audio speech?

[Walter Roberson]

Well if you can come up with an exhaustive list of all of the features in the world that are considered "conventional", then we could have a go at telling you which ones of them are present in audio speech.