Questions tagged [python]

Python is a high-level interpreted general programming language. Python has popular numerical and scientific libraries/packages, most notably numpy and scipy. The scipy.signal package is a powerful signal processing software collection. This tag covers the use of numpy, scipy, and other Python packages often used for SP computations.

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21 views

How can I append time series data into a finite array with a vanishing point?

I'm not sure what this is called in DSP terms, but I'm looking for a way I can append a new time series data point to an finite array and have it decay slowly over time. The best way I can visualize ...
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2answers
43 views

Deconvolution of an Image Acquired by a Square Uniform Detector

So, I acquired some images by scanning a radiation source with a square detector like in the following gif. Where the dashed grid represents reality, the 3x3 square my detector, and the 4x4 my ...
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27 views

ADSR parameter identification from envelope data

I'm trying to work out how to identify (or predict) ADSR parameters (attack time, decay time, sustain level and release time) from envelope data of real signal (or 'raw' data, but I think getting it ...
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1answer
23 views

How to allign audio signals after DTW?

Hello I am not a domain expert in signal processing but I need to align two audio signals. I have seen the following page https://librosa.github.io/librosa_gallery/auto_examples/plot_music_sync I ...
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26 views

Strange signals in wifi channel

I am currently working with a USRP B200 mini-i to receive 802.11 signals from various usb wifi devices. When sending packets with the USB device over a channel, lets say 2.412GHz, i can't really see ...
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1answer
57 views

How to manually implement convolution with FFTs?

I'm trying to manually implement a convolution using FFTs and it isn't working as expected. I know I'm probably missing some subtlety with padding, shifting, or conjugation, (all of which I've tried ...
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27 views

How to create different Time frequency images from a data

I'm new to Python. I have a time series in a CSV file that has about 5000 rows and 3 columns. I have split the data into training and testing in ratio 70:30 respectively. However, I have a problem ...
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6 views

Image extraction post processing to increase similarity

I’m trying to train an OCR model, but I need to get my extracted images to look more like the training images. However I’m not sure of how to go about it and what techniques I can use. For instance ...
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32 views

Kalman-Filter Estimate the position

I am quite new in this field and trying to learn Kalman-Filter but i am quite lost how to start my task. This is the file description Problem. I guess the state vector x must be the poistion of ...
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1answer
33 views

Comparing spectra from hyperspectral images

I extracted the mean spectra of regions of interests of different tissues from hyperspectral images. How to compare those spectra by the difference of their reflectance and their spectral behavior (...
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1answer
15 views

script to check zero crossings to check if microphones phases are aligned

I have 'n' microphones placed in square fashion and I want to make sure that all the channels must be aligned in time exactly the same if the signal is equidistant from all the 'n' microphones i.e. in ...
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1answer
33 views

generate a repeated square pulse train in python

Generate a pulse train with -2dBFS pulses of 20 sample duration every 8 seconds. I have referred here to generate a pulse train but not able to repeat it. How can I repeat this audio signal every 8 ...
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1answer
32 views

inverse discrete FFT in python, multiple times?

I was wondering what really happens when taking the inverse discrete FFT on some set of numbers, for 3 times? Because looking at it, it looks like we're getting an output that is identically with the ...
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20 views

modelling radar system for image generation

I am trying to find or derive some model for radar using python and blender which should hopefully create a simulation of what a radar image of the blender environment would look like. I have been ...
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177 views

Plotting a scalogram of a signal's Continuous Wavelet Transform (CWT) in python

So I've been learning about wavelets for a few weeks because I'd like to use them in a research project I'm working on and I've been trying to grasp the general ideas behind them.I've been struggling ...
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1answer
85 views

python3: speech recognition - calculating features of a WAV file

I am supposed to do this as a school project, but I am kind of lost when it comes to signals and would appreciate your help. Also, English is not my first language, and I will be translating the ...
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20 views

Can I get some help plotting an IIR filter frequency response in Python?

The problem I'm trying to solve is described here. In my script, I used Euler's identity to calculate z^-n, such that z^-n = cos(omegan) - jsin(omegan). I find the magnitude of these values from a ...
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1answer
54 views

How to plot the periodic digital spectrum?

In a previous answer, Dan Boschen wrote (emphasis mine): First let me explain the "unfolded" digital spectrum: If you allow the frequency axis of the sampled signal to extend to $\pm \infty$, ...
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23 views

Cepstrum calculation with 5-smoothing zero padding

I am trying to compute cepstrum of a signal x An implementation of this in python is: ...
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2answers
59 views

how can we align wto signals with a time lag in between?

I have two signals from two different sensors. I cropped the area i am interested in from both sensor signals. The problem is that the signals start at different time instants. I am searching for a ...
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37 views

Python resampling and filtering question

Intro Hi I'm looking for someone with some experience to walk me through some questions I have regarding resampling (downsampling) in Python. Here is my problem: I have accelerometer data that comes ...
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61 views

Trying to convert Raw image(Bayer format) to jpg/png image in Python

I am using the Sony Low-light image dataset from the paper Learning-to-see-in-the-Dark. I am trying to convert Raw image (bayer pattern in arw format) into a jpg/png. I used an online tool that gives ...
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1answer
36 views

How to measure algorithmically side lobes in real data

I want to measure algorithmically the following parameters in a given FFT data (real numbers). peak side lobe levels side lobe levels 
side lobes nulls The following image illustrates parameters I ...
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2answers
77 views

Why is my signal attenuated after applying a HighPass-filter?

I am new to DSP, but I've been attempting apply a butterworth high-pass filter on a 1D array (Values peeking at 300~) to eliminate any noise, yet when applying a high pass filter, I'm ending up with ...
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2answers
127 views

downsample signal to a specific number of samples in Python

The Python Scipy library provides several functions to downsample signals, but they all have limitations: The resample function is based on Fourier method, which means it assumes periodic signals. ...
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1answer
63 views

How can I correctly plot an impulse_response() of a discrete transfer function?

I posted this question on stack overflow and I think it was the wrong place so I moved it here. Hello, I'm new to python, I just want to use the control library and I'm slowly learning, I did my ...
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1answer
59 views

Large spike at beginning of signal after applying Bandpass filter

Foreword: I am a PhD student and fairly unexperienced with many signal processing and engineering concepts, please be gentle. I am attempting to filter out a frequency range of 1Hz to 2Hz from a 2....
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1answer
25 views

Applying a 2D band pass filter (Butterworth ?) to an array with NaNs

I am trying to filter out the low frequencies of an array looking like this : For now, I am taking transects of this array and applying a 1D - butterworth band pass filter : ...
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1answer
199 views

Running the BM3D Denoising Algorithm in Python

I am looking for a strong baseline in image denoising and therefore wanted to have the BM3D algorithm in my benchmark. These 2 python implementations: https://github.com/ericmjonas/pybm3d https://...
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1answer
120 views

Demodulation of FSK signal

What kind of FSK signal is this and what demodulation technique can I use to demodulate it. Why is the phase of the 1's changing like that and how does that effect how it needs to be demodulated. I ...
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1answer
53 views

SciPy Lfilter issue

For one of my DSP projects, I decided to use python to perform signal processing. While I am new to python, I understand that it is a very powerful and versatile language. For my processing, I opted ...
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5answers
283 views

What Are The Semantics Of Wav-File Sample Values?

The title is the question. To make this concrete, assume I have a standard 16-bit single channel wav file, with (although it doesn't matter) a 16000 Hz sampling rate. Each sample magnitude will be a ...
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1answer
33 views

which features fundamental frequency is correlated?

I'm unable to compute $f_0$ (fundamental frequency) in librosa feature extraction. By ready much in github issues check the second comment. I see that $f_0$ is ...
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1answer
46 views

numpy.linalg.lstsq underdetermined case

I would like to understand what I am doing wrong here. I am trying to perform polynomial regression by minimizing the least squares, ||Au-y||^2, where y is the given data and A is the matrix where the ...
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0answers
50 views

Stuck with plotting wavelet transform in Python

I want to plot the frequency composition of a sampled signal data versus time by using surf or any 3D plot. Normally time resolution of FFT is zero so I want to use wavelet transform where I want to ...
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0answers
12 views

Normalize a Mel-Spec over which axis?

I have to find out: how to normalize a Mel-spectrogram.(for mashine-learning purpose) However, I don't know which axis has to be transformed. The spectrogram S is of shape (m x n) where n are the ...
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1answer
84 views

Understanding Fourier Transforms in abstract math terms

I am having a hard time implementing a method that computes Fourier transform coefficients for the complex form using the trapezoid rule. I have floated questions in the math and stackoverflow ...
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1answer
83 views

get poles and zeros of frequency response

I am working on a python based LTSPICE project. I would like to get poles and zeros of AC simulation data. Is there a way to get them under use of the magnitude and phase out of the frequency ...
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1answer
35 views

estimation of ARMA(1,1) with MA parameter greater than 1

I am working with the following simple ARMA(1,1) model: $$ z_{t+1} = \phi z_{t} + \theta\varepsilon_{t} + \varepsilon_{t+1} $$ In my case $\theta$ depends on some other parameters, and, therefore, I ...
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0answers
14 views

Looking for a way to fill holes in objects, and break bridges between them

I am trying to extract building footprints from satellite images. Using a series of morphological operations i.e erosion and opening by reconstruction, I'm able to obtain the footprints, albeit with a ...
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0answers
141 views

Problem using pitch shifting with TD-PSOLA and formant preservation

I tried out this implementation of TD-PSOLA (https://github.com/sannawag/TD-PSOLA) and even though I know how the algorithm works, I can't understand why I get NO audible differences in the output ...
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2answers
56 views

How to detect real time sound onsets?

I'm a Software Engineer Undergraduate. I'm trying to detect drum strokes(beats) in real-time in python. I used amplitude threshold-based onset detect (beat detect) algorithm but it takes other noises ...
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0answers
46 views

How to compare imaginary coherence values?

High, I am currently writing my Master's thesis on susceptibility for hypnosis. I am comparing EGG signals of lowly and highly susceptible individuals. The imaginary coherence is given by: $$ \...
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0answers
50 views

How accurate is Python's FFT?

I am getting started with Python's FFT. I tested it on a signal that is a sum of three signals, two of which have an eigenfrequency of the grid, the third one does not (but due to large no. of data ...
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1answer
49 views

Real Fast Fourier Transformation (FFT) in 2D changes with changing the axes order

I am using Python to calculate the real FFT for a 2D array. I found that the real FFT function does not return an array with the same size as the input array, rather, it returns an array with the same ...
2
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1answer
73 views

KalmanFilter EM estimation of covariances

The question might be very simple, but I get a strange result from Kalman Filter. Let us consider the simplest state-space model, the random walk plus noise: $$ y_{t} = x_{t} + \varepsilon_{t}\\ x_{t} ...
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0answers
20 views

Calculating a transform with a circle and lines

I am trying to determine the transformation (rotation + translation + scale) between two images in order to shift them. The images are taken with two different modalities that produce very different ...
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0answers
39 views

Scaling x axis for FFTs in Python

I edited the post to be more specific, see below. I have a dataset, on which I need to perform and IFFT, cut the valueable part of it (by multiplying with a gaussian curve), then FFT back. First it's ...
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0answers
107 views

Does bicubic downsampling in PyTorch internally involve anti-aliasing?

Does bicubic downsampling in PyTorch torch.nn.functional.interpolate internally involve anti-aliasing? If not, how can we avoid aliasing when direct using bicubic ...
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0answers
10 views

Want to create a function that calculates the ISO and Shutter speed based on the brightness of previous image

I want to calculate the shutter speed and ISO of Picamera using the brightness information of the previous image I captured. I have already calculated the brightness of the previous image but I am ...