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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1answer
18 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 ...
0
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1answer
18 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 ...
1
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0answers
6 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
34 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) ...
0
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0answers
44 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
votes
1answer
119 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 ...
1
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1answer
44 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 ?
0
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1answer
27 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
34 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 ...
1
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0answers
66 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 ...
0
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2answers
85 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 ...
0
votes
1answer
117 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. ...
0
votes
2answers
40 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
0
votes
1answer
26 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 ...
0
votes
2answers
53 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 ...
0
votes
2answers
110 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 ...
1
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0answers
24 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
34 views

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

Is this possible to work with PYTHON or C in MATLAB.
3
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2answers
84 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
votes
1answer
123 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 ...
1
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0answers
48 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 ...
1
vote
1answer
118 views

Basic question about chirp signal

Suppose I generate chirp signal with the following python code: ...
2
votes
1answer
120 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
votes
2answers
125 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 ...
0
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0answers
59 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 ...
0
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2answers
139 views

Negative values of the FFT

I try to describe a simple signal in the frequency domain with the use of FFT function: ...
0
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0answers
159 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 ...
0
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1answer
82 views

Strange phase spectrum from stft

I've tried to implement STFT in functional way in Python. I've got code such as below: ...
0
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0answers
34 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
77 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
votes
1answer
65 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
votes
1answer
164 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 ...
0
votes
1answer
192 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
votes
1answer
164 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
176 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 ...
0
votes
1answer
763 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 ...
0
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0answers
24 views

choosing how many DWT Decomposition levels for 1D

I am building application decomposition of 1D signal sampling frequency $f_s=256$, number of samples $N=512$ - how many levels if the above signal passed through LPF of $70 Hz$ $f_s=256$, number ...
1
vote
1answer
85 views

Sub pixel shift causes weird results

I am trying to shift an image on a subpixel level, with the method described here: ...
1
vote
1answer
73 views

The Nyquist-Theorm behind the fft

I saw a code in Python in the scipy.org (http://docs.scipy.org/doc/scipy-dev/reference/tutorial/fftpack.html) and found this: First question: Is it right that T = 1/800 <==> fs = 800 Hz fulfill ...
0
votes
1answer
45 views

Record and playback has echo/feedback

I didn't mess around with the code here, it was straight from their website, I just want to see if it would work. However, whenever I run it, it has feedback in it, sometimes I can't hear anything at ...
0
votes
1answer
84 views

Why do we need to normalize a WAV file before calculating the FFT?

I am trying to calculate the FFT of a signal stored in a WAV file using SciPy. I found a solution here, but it seems like we need to perform this step before the FFT: ...
0
votes
1answer
52 views

One representative time series signal from multiple time series data

I came across this basic problem in DSP which is not my area owf expertise but I consider this problem to be a common problem which others might be addressing. I have multiple time series data and I ...
0
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0answers
50 views

Feature extraction - DWT

I am new to DSP, I know a quite bit about Python. I have started to code to classify audio (wav files) ...
0
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0answers
73 views

Template matching results when the template is not on the original image

For testing purposes I'm building a bot that clicks on buttons in the screen. I have a folder with all the possible buttons that needs to be pressed and the application being tested only has one ...
2
votes
1answer
946 views

Applying filter in scipy.signal: Use lfilter or filtfilt?

I saw in a SO thread a suggestion to use filtfilt which performs backwards/forwards filtering instead of lfilter. What is the ...
2
votes
1answer
172 views

Butterworth filter in python

I'm trying to use a Butterworth filter in Python as described in this thread with these functions: ...
1
vote
2answers
60 views

Smooth X,Y,Z data with discontinuous, artificial jumps

I have some data $(X,Y,Z)$, which is a set of measurements $Z$ over a $2D$ space $X$,$Y$. The $Z$ data on this space is continuous except for some discontinuous jumps in certain domains of $X$,$Y$ ...
0
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0answers
83 views

Python implementation of multidimensional power spectral density with Welch method

I have done my best to write Welch method implementation for python for multidimensional time series and still in the case of one dimensional time series I am getting inconsistent response compared to ...
2
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0answers
112 views

Extracting the phase of a jittering sine wave using python

The background: I conducted an experiment where I rotated an object (with three-fold symmetry) many times and recorded the projection of the object. I should be able to tomographically reconstruct ...
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0answers
168 views

In a signal there is a peak, I want to find the start of the peak and the end of the peak

I want to the start time and end time for the peak shown below. The start and end are shown by the marked circles in the fig As there are number of such plots and want to know start and end time for ...