Questions tagged [stft]
Short-Time Fourier Transform
307
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STFT normalization
In Scipy's implementation of STFT, an argument allows to scale the result as a spectrum or as a psd :
...
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Why not overlap save for inverse stft
Since STFT uses overlapped sections of the input signals and compute DFT, it resembles overlap-save method used for block convolution, instead the overlap-add method for block convolution uses non-...
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reproduce Scipy's stft
I failed to reproduce Scipy's stft. When I have tried to remove all the possible modifications and go the minimal example, I converge to the following:
...
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How to implement STFT for processing audio [closed]
I should start this off by saying I’m a hobbyist and by no means a student. I’ve been reading “The Audio Programming Book”, and attempting to implement STFT on the stm32 based Daisy platform.
In order ...
2
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What is the difference between STFT and Gabor filter?
My understanding is that a Gabor filter gives us information about when in the input signal does the frequency of interest (equal to the frequency of the sinusoid in the Gabor Filter) occur, thus ...
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Comparing results for spectrum generating in matlab using STFT and Filterbank approach
To analyse data in the frequency domain I often use functions like stft() in Matlab. Inspired by this video and this article I have compared the results of ...
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Overall spectrum computation from Short-Time-Fourier-Transform
I am trying to computing the overall spectrum of a given signal from its Short-Time-Fourier-Transform. I am using python to do this and I wrote my function to compute the STFT:
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Unwindowed STFT of sine, closed form solution and insights (sliding FFT)
I seek to calculate, mathematically, the unwindowed Short-Time Fourier Transform of
$$
\cos(2\pi f t + \phi)
$$
i.e. any arbitrary real-valued sine: any frequency, duration, phase shift, and number of ...
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Artifact during this STFT spectrogram plotting
I am new to the field of DSP and I am currently working on implementing a real-time audio spectrogram using STFT technique.
While making progress, I have encountered an issue when testing a constant ...
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STFT Audio processing with zeros
In this paper they preprocess an audio file with a STFT and then apply two equations to the computed matrix.
I tried implementing all of it in python and used librosa for the STFT.
The issue I ...
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STFT needs circular shift or not?
In some textbooks and websites, circular shift operation is done before doing FFT of windowed data, in the explaination, circular shift is to ensure zero-phase. But in other textbooks and websites(I ...
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Increasing STFT resolution by repeating the window? Ways to improve STFT resolution?
In theory of FT(Fourier transform) and STFT(Short Time Fourier Transform) it is said that "A narrower window gives good ...
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How would you compute Fourier transform of a real world signal where the signal keeps getting updated (not a static one)?
Crossposted at Electrical Engineering SE
A very naive question: How do we use Fourier transform for real world signals - for which you have the information only up to the present instant (and the ...
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Construction of Room Impulse Response - Short-Time-Fourier-Transform and Inverse-STFT - Matlab and NWaves (C#) Implementation
Background:
I am working on a Unity Project (C#) and implementing a Room Impulse Response synthesis.
I do ray tracing to create energy histogram for different bands.
With these histograms it is ...
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How does the effect of windowing change with the phase of the input signal?
I am calculating the SNR (signal power to noise power) for a sine wave. I don't have an integer number of periods in the waveform being analyzed, so I am using a flattop window to reduce spectral ...
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How do `n_fft` and `win_length` determine the window in spectrogram?
I am currently trying to understand librosa.feature.melspectrogram in a mathematical sense.
In my understanding, spectrogram is based on the STFT which is for a ...
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Scipy and Matlab Spectrogram not matching
I am trying to replicate a spectrogram from MATLAB in Python. I've read other posts but they either don't use complex data or the data doesn't match between languages.
I've defined my FFT length (<...
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Reconstruction of batch-acquired signal
I am currently working on a project which requires evaluating slow changes over time in the magnitude of a signal's high frequency (over 10 kHz) components.
This signal was acquired in tests with a 25....
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Equivalence between "windowed Fourier transform" and STFT as convolutions/filtering
I've heard, that "windowed Fourier transform" is but one perspective on STFT, and that STFT is fundamentally convolutions of windowed complex sinusoids with the input, i.e. bandpass ...
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How to calculate phase estimation error
I am working on speech enhancement and I want to compare the phase and magnitude between two signals. I compute the STFT for both, and comparing the magnitudes is easy via mean-squared error or some ...
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A mathematical justification of discontinuity detection using STFT
I'm trying to detect rapid changes in a one-dimensional signal say $[0,1]\ni t \mapsto f(t) \in [-1,1]$. By rapid changes, I mean corner points, edges, or sharp transitions at a point for example the ...
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Amplitude extraction using STFT
I'm trying to recover amplitude/magnitude from an audio stream. I'm using FFT to go from time domain to frequency.
If I feed in a signal of known amplitude, the results I get from either windowing or ...
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Overlap and Add/Save Inverse Short-Time Fourier transform
Edited for conciseness, please see below:
Question: How does overlap and save work, in the context of array buffers? How does overlap and add work? For a specific use case involving STFT, which one is ...
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Does overlapping windows while processing a signal produce a stretched time domain?
I'm very new to signal processing and attempting to implement a spectrogram generator to learn more about DSP in general. So far, I have built up an understanding of how I might do that.
Get input ...
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difference in speed between tensorflow implementations of mfcc and stft
I am trying to preprocess audio clips for a keyword spotting task that uses machine learning models.
The first step is to calculate the spectrogram starting from the waveform and in order to do so I ...
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700
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Wigner-Ville Distribution (WVD) vs STFT for Spectral Analysis
What are the Pros and Cons of using Wigner-Ville Distribution for spectral analysis of a signal vs taking the STFT. When is it appropriate to use one over the other and is WVD used in real-time ...
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How to detect "buzz" components in audio by frequency domain analysis
I am trying to detect the amplitude, frequency and phase of the dominant "buzz" in an audio signal. By "buzz" I mean a periodic signal with sharp edges. For example, an impulse ...
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Spectrum analyzer with multirate filter bank
This paper gives a spectrum analyzer using the multirate filter bank technique. The basic idea of the paper is that STFT can be interpretated as a uniform DFT filter bank. But the baseband filter of ...
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How to plot the STFT of a .wav file in GNU Octave?
I'm quite new to signal processing and am trying to find the short time fourier transform of an audio sample and plot it (I believe the best way is as a spectogram?) using Octave (similar to this ...
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Choice of relationship between n_fft and window_length in STFT
Not a veteran in Signal Processing, it would be extremely appreciated to help me understand the idea/heuristic behinde the idea in STFT that
$$\text{nfft} \ge \text{window length}$$
At least from a ...
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What is the cause of STFT artifacts when different signals overlap?
I'm trying to learn about why signals that cross in an STFT cause apparent artifacts in the magnitude. I've been looking at the example below, written in python, where a gaussian peak overlaps with a ...
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STFT for Classification
I am working on this project in which I am using Short Time Fourier Transform (STFT) for feature extraction before applying classification model. I have a time series sensor data, applied signal ...
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Why does varying n_fft change the range of x axis values when plotting STFT?
I am using librosa.stft to apply an STFT to an audio sample and display a spectogram of the results when using different sampling windows (...
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Why does NMF (Non Negative Matrix Factorization) decompose a spectrogram into time and frequency component?
I compute the NMF over a spectrogram (magnitude of STFT of a signal) in this way:
W,H = NMF(MyStft,r) # where r=2 is the rank
W and H respectively contain the ...
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Spectrogram of a shock event
I have measured data of a vibration with chirp input were I suspect unwanted shock events occurred.
I therefore thought about computing the spectrogram of my time histories to check the frequency ...
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Filterbank Interpretation of Inverse STFT With Hop
The slide below, borrowed from CMU, shows the typical interpretation of the "filterbank interpretation" of signal reconstruction from a Short Time Fourier Transform. As far as I can tell, ...
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How to calculate short-time fourier transform (STFT) when the window length is greater or smaller than the FFT size?
I have been trying to understand the weighted overlap-add (WOLA) method. By searching papers and posts in dsp.SE, I found that the window length can be larger and smaller than the FFT size.
1. Window ...
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How to create overlapping frames of input signal for stft using HDL coder for FPGA implementation?
I want to implement stft on FPGA. For this purpose I use HDL coder and the problem is I have no idea how to create overlapping frames of data for further FFT. In my example I want to use 256 frame ...
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Impact of STFT window function and FFT length on computation time
I have been doing a study which part of it includes a comparison of computation time vs window type and length (among some other things in the computation time, however I speak in terms of relative ...
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Best way to get the bin amplitudes of an audio DFT "normalized" 0-1
I'm working on a spectral processing plugin that's predicated on allowing the user to manipulate per-bin values in an STFT algorithm. I normalize the bin amplitudes by diving them by $N$ (number of ...
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1
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276
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Performing STFT after Butterworth Filter Seems Lower in Resolution
I have a signal recorded at 2MHz sampling rate. Before any decimation might be required, I first looked for peaks in my periodic recorded signal using STFT/spectrogram. From here, I can clearly see ...
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Calculating Short Time Fourier Transform Manually
I am doing a project on short time Fourier transform, I have to perform STFT for 128 data points. I have developed a Matlab code to perform the STFT operation. But, my main concern is, I need to ...
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Classifying STFT from multiple signal samples
I have a collection of signals (IQ wav) split up into ~2s samples of sampling rate 2MHz, and can collect the STFT information from these samples through the following code:
...
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Is it possible to classify signal samples using STFT without (image-based) spectrograms?
I am aiming to conduct a classification-based study using signals collected from various devices. I've researched other approaches which make use of STFT for producing a spectrogram for speech and EEG/...
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Reconstructing Audio From Spectrogram (Using it as a filter)
Given a spectrogram calculated using the following code:
...
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normalize STFT output by magnitude
I am using torch.stft() to generate spectrograms for neural networks and come across the below code.
...
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Strong vs weak COLA (constant overlap-add)
My question is on the aliasing cancellation of the OLA method when spectral modification is involved. The book related to this question is given by this link.
As stated by the webpage, for weak COLA ...
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Optimize window length (STFT) via gradient descent (in neural networks)
The authors from this paper optimized a Gaussian window size via gradient descent (the σ parameter of the bell curve) together with the other parameters of neural networks.
I don't use Gaussian window ...
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Calculate number of buzzs and their duration
I'm trying to calculate the number of buzzs and their duration from a buzzer. I'm working with python and scipy lib and the short time fourier transformation capturing the audio with a microphone.
To ...
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How to zero pad and do overlapping block convolution to reconstruct audio for frequency filtering in time-frequency domain
I am doing STFT (short-time Fourier transform) on real-time audio to filter frequencies by magnitudes (to reduce noise) which have certain drawbacks like noise spikes in reconstructed audio in the ...
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