Stft

torch_stft(
input,
n_fft,
hop_length = NULL,
win_length = NULL,
window = NULL,
center = TRUE,
normalized = FALSE,
onesided = TRUE,
return_complex = NULL
)

## Arguments

input (Tensor) the input tensor (int) size of Fourier transform (int, optional) the distance between neighboring sliding window frames. Default: NULL (treated as equal to floor(n_fft / 4)) (int, optional) the size of window frame and STFT filter. Default: NULL (treated as equal to n_fft) (Tensor, optional) the optional window function. Default: NULL (treated as window of all $$1$$ s) (bool, optional) whether to pad input on both sides so that the $$t$$-th frame is centered at time $$t \times \mbox{hop\_length}$$. Default: TRUE (string, optional) controls the padding method used when center is TRUE. Default: "reflect" (bool, optional) controls whether to return the normalized STFT results Default: FALSE (bool, optional) controls whether to return half of results to avoid redundancy Default: TRUE (bool, optional) controls whether to return complex tensors or not.

## Short-time Fourier transform (STFT).

Short-time Fourier transform (STFT).

Ignoring the optional batch dimension, this method computes the following
expression:


$$X[m, \omega] = \sum_{k = 0}^{\mbox{win\_length-1}}% \mbox{window}[k]\ \mbox{input}[m \times \mbox{hop\_length} + k]\ % \exp\left(- j \frac{2 \pi \cdot \omega k}{\mbox{win\_length}}\right),$$ where $$m$$ is the index of the sliding window, and $$\omega$$ is the frequency that $$0 \leq \omega < \mbox{n\_fft}$$. When onesided is the default value TRUE,

* input must be either a 1-D time sequence or a 2-D batch of time
sequences.

* If hop_length is NULL (default), it is treated as equal to
floor(n_fft / 4).

* If win_length is NULL (default), it is treated as equal to
n_fft.

* window can be a 1-D tensor of size win_length, e.g., from
torch_hann_window. If window is NULL (default), it is
treated as if having \eqn{1} everywhere in the window. If
\eqn{\mbox{win\_length} < \mbox{n\_fft}}, window will be padded on
both sides to length n_fft before being applied.

* If center is TRUE (default), input will be padded on
both sides so that the \eqn{t}-th frame is centered at time
\eqn{t \times \mbox{hop\_length}}. Otherwise, the \eqn{t}-th frame
begins at time  \eqn{t \times \mbox{hop\_length}}.

* pad_mode determines the padding method used on input when
center is TRUE. See torch_nn.functional.pad for
all available options. Default is "reflect".

* If onesided is TRUE (default), only values for \eqn{\omega}
in \eqn{\left[0, 1, 2, \dots, \left\lfloor \frac{\mbox{n\_fft}}{2} \right\rfloor + 1\right]}
are returned because the real-to-complex Fourier transform satisfies the
conjugate symmetry, i.e., \eqn{X[m, \omega] = X[m, \mbox{n\_fft} - \omega]^*}.

* If normalized is TRUE (default is FALSE), the function
returns the normalized STFT results, i.e., multiplied by \eqn{(\mbox{frame\_length})^{-0.5}}.

Returns the real and the imaginary parts together as one tensor of size
\eqn{(* \times N \times T \times 2)}, where \eqn{*} is the optional
batch size of input, \eqn{N} is the number of frequencies where
STFT is applied, \eqn{T} is the total number of frames used, and each pair
in the last dimension represents a complex number as the real part and the
imaginary part.


## Warning

This function changed signature at version 0.4.1. Calling with the previous signature may cause error or return incorrect result.