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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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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1answer
1k views
Adaptive Piecewise Constant Approximation (APCA) with wavelets/DWT
I am trying to approximate a vector or a time series, in order to have as little changes as possible. To do so, I pretend to apply the Adaptive piecewise constant approximation (APCA) algorithm. ...
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1answer
124 views
how to extract a radio signal features with python?
I have a dataset of radio signals that i want to classify. So, I decided to extract features. After some googling, I have noticed that I have to calculate moments, cumulants, Kutosis and skewness to ...
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2answers
135 views
I wish to create a GNU Radio program in C++ that doesn't need GRC or Python, is there a reference or template for this?
I want to create a functionally equivalent C++ file to the Python top_block.py file that is generated by GRC when executing a (blank example) flow chart.
I know that C++ can be used to define blocks ...
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1answer
608 views
Filter ECG signal with Wavelet and Python
I have to filter the signal of an ECG with the wavelet method with Python. The data is in a txt file. I can create my dataframe with pandas, display that with seaborn, but can not find a way to apply ...
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1answer
2k views
Python: Least Squares Support Vector Machine (LS-SVM)
I'm looking for a Python package for a LS-SVM or a way to tune a normal SVM from scikit-learn to a Least-Squares Support Vector Machine for a classification problem.
The goal of a SVM is to maximize ...
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3answers
2k views
Implementation of Wikipedia Equation for the DFT
I was writing a simple fourier transform implementation and looked at the DFT equation on wikipedia for reference, when I noticed that I was doing something differently, and after thinking about it ...
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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
55 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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3answers
137 views
dft of sampled sine using python
I'm trying to write a python script to perform a 100-point DFT over a finite length sample of a sinewave at 1/8 the sampling frequency. I'm curious why my DFT magnitude plot has two spikes in it when ...
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1answer
2k views
Shift in Time Domain After DFT Based Convolution
To my understanding, multiplying a signal in the frequency-domain is equal to a convolution in the time-domain.
I wrote a small python program, but i always end up with a shift in the time domain. ...
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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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1answer
1k views
Bandpass filter for audio wav file
How do I apply a bandpass filter on an audio file which is in wav format?
And write back the filtered data in a new wav file for further analysis.
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0answers
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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1answer
695 views
How is WSNR (weighted signal to noise ratio) defined?
I'm studying about comparison between images to determine quality. I've learned about MSE, SNR and PSNR, and now I'm trying to understand WSNR, which I assume is similar to SNR but with weights.
I ...
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0answers
31 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
297 views
How to find the probability of Kalman filter states? [OpenCV+Python]
I am working on a video object tracking problem. I am using Kalman filter to predict and correct the object position return by an algorithm such as CamShift. I want to adjust the likelihood ...
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1answer
555 views
Python tool for time-frequency analysis
I am trying to perform time-frequency analyses using the PyWavelets (pywt) toolkit for python. My ultimate goal is to perform time-frequency analyses for EEG signals but I am starting with something ...
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2answers
57 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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1answer
1k views
Issues with the smoothing operator in coherence estimation using the complex Morlet (Gabor) wavelet
The goal
I wish to compute the coherence estimate using the continuous wavelet transform (CWT) of a real-valued signal with the complex Morlet (a.k.a. Gabor) wavelet. I compute the cwt of the signal ...
0
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1answer
490 views
Confusion with data after cross correlation
Surely this question has been answered before in parts but I cannot find one solid answer. Ultimately I am trying to calculate the audio delay between two signals I am recording on USB microphones. ...
0
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1answer
99 views
reconstructing time-stretched signals for filtering purposes
I would like to know if it's possible to reconstruct the original time domain signal from it's time-stretched version? Is there any algorithm out there that can do this? Python, Matlab, etc?
I want ...
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1answer
2k views
How can we know the geometry of a blob detected by OpenCV
I am performing blob analysis using connectedComponentsWithStats, which returns elementary statistics about the blobs (AABB and area). It is also possible to ...
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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 ...
0
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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
30 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
366 views
Machine Learning - any suggestions to solve Python rounding errors?
I am working with Python to isolate voiced segments from music using the Jamendo corpus for singing detection. Training a model, I break my audio into frames, and have a label (0,1) for each frame.
...
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3answers
27k views
Apply Low pass Butterworth filter in Python
I want to use a low pass Butterworth filter on my data but on applying the filter I don't get the intended signal. Here is the dummy code:
Signal A:
...
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2answers
5k views
Implementing inverse FFT using forward FFT
I am trying to implement an inverse FFT using the forward FFT. For clarity:
Let S[t] be a signal in time, and S[w] the transformed signal. As per this site, it seems one can reverse S[w], use the ...
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1answer
649 views
Is there a way to obtain the transfer function from a bode plot on Python? (I know that it is possible on Matlab)
Quite simply, I have a bode plot obtained from a source signal.
Now I wish to obtain the transfer function.
I know it is possible with Matlab: http://www.mathworks.com/help/ident/examples/frequency-...
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1answer
128 views
Low-Pass Filtering of not evenly sampled signal
I have a signal sampled unevenly over 1 million ns.
the signal is sampled over 1GHZ clock and the samples are as the following:
0-100 ns - sample every 1 ns.
100-1000 ns - sample every 10 ns.
1000-...
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1answer
1k views
Are there any signal processing libraries that implement TD-PSOLA?
For such a popular and old algorithm, I've had surprisingly little luck finding implementations. I've got it working in MATLAB, but am curious if any other languages have libraries containing it (...
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1answer
2k views
Comparing Welch and FFT power spectrum density
Based on previous answers from the forum, I implemented a function to compute the Power Spectrum of a 1D time series.
...
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1answer
4k views
Demodulating FSK audio in Python
I am trying to write a Python script that can demodulate an FSK modulated audio file and return the data encoded in the audio. The data being transmitted is GPS NMEA strings which are embedded as the ...
0
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1answer
96 views
Discrete-time, second-order section, direct-form II filter
I found dfilt.df2sos in Matlab and trying to figure it out how do I do that in Python? Is there any function that works similarly with the Matlab function?
I also ...
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0answers
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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1answer
12k views
Discrete Wavelet Transform - Visualizing Relation between Decomposed Detail Coefficients and Signal
I'm trying to directly visualize the relation between discrete wavelet transform (DWT) detail coefficients and the original signal/its reconstruction. The goal is to show their relation in an ...
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1answer
178 views
High resolution spectrograms
I have a recorded audio signal that I would like to convert into spectrogram with the highest possible yield of information.
The audio clips I am working with is about 30 ms long and contains ...
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2answers
772 views
Determine if two signals are the same?
I'm pretty new to signal processing. My data is the $(x,y,z)$ acceleration of someone walking with a smartphone in his/her pocket.
Goal
Given two signals, determine if it's from the same person ...
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1answer
43 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
146 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
366 views
Binarization, and then thinning/skeletonization
I have pictures of networks, like the one below, and my goal is to obtain the network's skeleton from processing those images.
My approach lies in two steps, first I convert grayscale image to binary ...
2
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1answer
629 views
(python+opencv) haar cascade training using cloud computing
I will train my own cascade, using python and opencv. I want it to be as precise as possible, so as I read it is common that training takes one or two weeks to compile. I want to use cloud computing ...
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1answer
2k views
Computing the Power Spectrum Density (PSD) on a CSV File in Python
im quit new with signal processing and im trying to calculate the PSD of a signal im sampling. the signal is an output of a DC buck converter
this is the code im using and this is the plot im getting ...
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2answers
146 views
Shifting signal smaller than discrete step
I have a image that I need to shift with less than a pixel.
My plan was to do a Fourier transform and multiply the signal with $e^{-aiu-biv}$ where $a, b$ are the shifts in x and y direction. This ...
2
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1answer
82 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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2answers
7k views
Avoiding “RuntimeWarning: invalid value encountered in log10” when converting FFT data to dBFS
I've attached some code below that I'm having some issues with. Basically, I need to write a function to get the dBFS value of a signal at a specified Hz value, at a given channel in a .wav file. ...
0
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1answer
89 views
Detect gradual increase then decrease in slightly noisy data
I have data thats not too noisy and I am trying to detect a pattern where it gradually increases then decreases in a short period of time (20 ticks? it should be roughly similar per session but can ...
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1answer
171 views
Extract approximation and detail coefficients
I am a student and would like to know how to extract the approximation and detail coefficients (A5, D5, D4, D3, D2 and D1) after an applied DWT decomposition dB5 (Daubechies 5, level = 5)?
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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 ...
