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 ...

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52 views

Nyquist Frquency isn't what it is supposed to be

I am new here and also am not very knowledgeable about DSP so this might be dumb and easy. I am aware of the fact that in order to reconstruct a signal, I need to sample it at a frequency that is more ...
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0answers
13 views

Plotting Discrete Wavelet Transform in Python

I'm using Pywavelets to perform a discrete wavelet transform on a signal, which returns the approximation and detail coefficients as a list of float64 1d arrays with increasing size. I was wondering ...
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1answer
17 views

Image processing usign conv-neural net

Okay I am starting to understand the idea of neural networks but I still haven't been able to understand the use/benefits/implementation of convolutional neural networks especially for image ...
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10 views

sklearn - overfitting problem

I'm looking for recommendations as to the best way forward for my current machine learning problem The outline of the problem and what I've done is as follows: I have 900+ trials of EEG data, where ...
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0answers
8 views

Python MNE - reading EEG data from array

I have EEG data that comes in the form of a 3D numpy array (epoch * channel * timepoint). timepoint is a 256 element array containing each sampled timepoint (1s total, at 256Hz). epoch is an ...
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1answer
46 views

Generating a noisy sine wave in Python, efficiently

(Questions after code block.) For now, I am generating the sinusoid and the noise separately and then normalising the amplitude so I can write the signal to a .wav file (16-bit, 16kHz). ...
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1answer
74 views

Python - time frequency spectrogram

I have some 64 channel EEG data sampled at 256Hz and I'm trying to conduct a time frequency analysis for each channel and plot a spectrogram. The data is stored in a numpy 3d array, where one of the ...
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1answer
19 views

Chromatography Baseline Placement

I have been looking around on Google, and I have not been able to find an explanation of how to do baseline placement in chromatography. what are some algorithms for placing a baseline on a ...
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1answer
64 views

Python bandpass filter - singular matrix error

I've been trying to design a bandpass filter using scipy but I keep getting a LinAlg Singular Matrix error. I read that a singular matrix is one that is not invertable, but I'm not sure how that error ...
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1answer
32 views

simulating noise with Yuler and burg

I want to simulate short term white noise with Yuler and Burg. It's said that it can give better results than Gauss-Markov. The problem is that each time the series diverge. Do you think that I made ...
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45 views

Noise reduction on wave file

I have created a simple plot of waveforms using matplotlib of 2 wave files on python. Here is the code: ...
2
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2answers
54 views

Is it appropriate to use PSD on the analysis of a plucked guitar string?

I'm using python 2.7 to compare tonal differences in guitar stings. I've found that in matplotlib, there are some great built-in features such as matplotlib.mlab.magnitude_spectrum and ...
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0answers
35 views

Image Subtraction using Pre-bayer data (.pgm)

Not sure if this is the best stack exchange but I'll give it a shot. I am performing background subtraction to collect Electroluminescent emission (i.e image w/ emission - image w/o emission = ...
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2answers
42 views

noise remains after applying median filter

So I'm apply the median filter to an image, but at the output, there's blue semi-dots appearing. What are they? This is the output And the python code for anyone interested ...
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1answer
50 views

Real-time frequency recognition in python

I'm a newcomer to signal processing, so forgive my ignorance. I'm working on a project in Python that will play a .wav file and pick out the dominant frequency as it plays. I've found a few examples ...
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1answer
49 views

Why does the specgram of this simple sine wave look strange?

I'm trying to test some intuition using the matplotlib specgram routine. I first generate a simple sine wave ...
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0answers
15 views

Singularity Detection from 2D Wavelet Modulus Plot

I was wondering if I could get some tips/resources on how to pick out the singularity from my 2D Continuous Wavelet Transform Coefficient Plot (scalogram) using the Gaussian Derivative as the ...
0
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1answer
60 views

Generate fourier transform signal

I'm newbie in DSP (maybe the question title is misleading for this reason, I apologize for this, please feel free to edit it) but not in programming. I want to experiment with Fourier (or FFT) ...
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0answers
49 views

Cannot see effect of modifying eigen values in Python (SciPy, NumPy)

I am doing some experiment for increasing the intensity of low exposure image by changing (increasing) the eigen values. In Matlab I apply Singular Value Decomposition on the image matrix to get ...
4
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1answer
140 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 ...
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1answer
116 views

K-means for 2D point clustering in python

I have a set of points(2D) whose pixels are set and want to perform k-means on these pixels. Is clustering the 2D coordinates the right way ? If so, can that be done using any libraries in python ?
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1answer
41 views

Applying a mathematical function to a 16-bit Python array

I am using scipy.io.wavfile to read a WAV file and playing it with pyaudio. Before the numpy array is written to a string and output through pyaudio, I would like to be able to apply some sort of ...
2
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0answers
42 views

How many different filters are needed for in an iterated filter bank?

I'm trying to implement an iterated filter bank as described in the Subband coding chapter of the Really Friendly Guide to Wavelets. However, the text seems to suggest that The advantage of this ...
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0answers
85 views

How do I interpolate between bins on an FFT in python?

I have four frequency peaks, which I have after applying FFT. Now I want to know precise values of these frequency peaks. there are different interpolation methods. How can I use this method of ...
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2answers
118 views

Dominating frequency in a “clear” 50 Hz signal

I am trying to find out the dominating frequency of a signal with a frequency of 50 Hz (sampled at 200 Hz - every 5 milliseconds). The python code I am using to do this is the following (based on ...
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1answer
144 views

Shift in Time-Domain after FFT-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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2answers
60 views

How can I get maximum complex value from an array of complex values(524289) in python?

I have an array of complex values. Actually this array contains fast Fourier transformation fft values. now I want to fetch maximum complex value from the array. Thanks
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51 views

How to apply the least squares method to built-in models of Levenberg-Marquardt algorithm

I am trying to apply the least squares to my data using the built-in Voigt model from lmfit. But I have to call the Minimizer class to apply the least squares method, which requires a function. And ...
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2answers
75 views

Phase spectrum range

I computed spectrum analysis of sine wave (without windowing and zero-padding) and I got plots as follows: As far as I know they are correct. When I learnt about DSP, I got the huge problem with ...
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2answers
172 views

Image processing (number recognition) woes

So I have the following image: Using GIMP, I was able to get to here: Select all white color (with a touch of fuzz) Invert selection Cut selection Invert all color (goes black) But now I'm ...
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0answers
26 views

scaling issue when using scypy's firwin2 to get coefficients for a filter

I am trying to use SciPy's firwin2 command to get the coefficients that correspond to a filter of my creating. I took white noise in Audacity, applied an ...
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1answer
36 views

What programming language is going to use MATLAB programming? [closed]

Is this possible to work with PYTHON or C in MATLAB.
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2answers
97 views

Initial state recognition in HMM

I am building a speech recognition system using Hidden Markov Model in python. I referred to this and this question and its answers, which were very helpful. In my approach, I split the continuous ...
2
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1answer
216 views

How should I select window size and overlap?

I'm new to DSP and I have a wav file with a number of different frequencies playing at different volumes. I'd like to plot the power of the 350Hz frequency signal at each point in time. The source is ...
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0answers
56 views

How to process the .wav file to get meaningful information like the number of inhales/exhales

The plot of the data from the wav file. Link to the sound file - https://drive.google.com/open?id=0BxAPlY66uX7qWWtDZUw3WkpjSGs&authuser=0 Also the FFT plot is like this I am new to the field ...
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1answer
138 views

Basic question about chirp signal

Suppose I generate chirp signal with the following python code: ...
2
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1answer
147 views

Detecting phones in a word audio

I am working on speech recognition for Hindi language. My approach is to map speech to text based on phones. For this, first split the speech into the words and then map each word to text by detecting ...
3
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2answers
145 views

How to identify useful elements of audio recording and ignore lulls?

I assume this is a relatively simple DSP task, but I'm having trouble finding any information on how to approach my problem. Hopefully someone with more experience and brain power can help me out: I ...
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0answers
81 views

How to compute Gradient of an image with kernel in python

Using python numpy or scipy I am trying to perform cross-correlation on each pixel of an image using a 3 dimensional kernel. I am more interested in looping into each pixel and applying the kernel ...
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2answers
215 views

Negative values of the FFT

I try to describe a simple signal in the frequency domain with the use of FFT function: ...
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0answers
218 views

How can I make the background color white for this Grab-cut algorithm written in Python?

I am new to Image Processing and am using Grab cut algorithm to extract the foreground objects from images as a part of my project. Below is the code written in python to do the same. The problem is ...
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1answer
93 views

Strange phase spectrum from stft

I've tried to implement STFT in functional way in Python. I've got code such as below: ...
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0answers
43 views

Implementing capons spectral estimator in python

I am trying to implement capons high resolution frequency-wavenumber spectral estimator (mvdr) for use with data from an isotropic array. My results were unstable so I use diagonal loading. I am a bit ...
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0answers
93 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 ...
0
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1answer
77 views

Apply FIR filters to Extract Stego from WAV data

I appreciate anyone that takes a moment to help me with this problem. I've been banging my head against the keyboard for a while, searching forums and DSP tutorials and I can't figure this problem ...
0
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1answer
235 views

Confused with convolutions in scipy

I tried to write my own circular convolution function in python using the fact that for two signals $f$ and $g$ we have $$ \widehat{(f * g)} = f \cdot g $$ So I tried this ...
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1answer
240 views

Removing periodic noise from image using Fourier transform

I'm trying to get rid of some periodic flicker noise through post-processing of the recorded images. The reason for these artifacts is that the electronic rolling shutter of the camera reads each line ...
0
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1answer
245 views

Histogram matching (specification) in Python

I'm trying to implement an algorithm in which I first pad each row of the image with a fixed amount of new pixels in a certain range, apply Gaussian smoothing to the row cumulative histograms in ...
3
votes
1answer
217 views

Is it possible to hack camera calibration without having access to the camera?

Many times we have a stream of video to process without access to camera. Having access to camera matrix would be beneficial for various processing techniques. Is it possible to hack camera ...
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1answer
981 views

OpenCV Motion Analysis: Optical Flow vs Motion History

OpenCV Motion Analysis Documentation lists multiple techniques for motion tracking: Sparse Optical Flow | calcOpticalFlowPyrLK, Dense Optical Flow | calcOpticalFlowFarneback, and Motion History ...