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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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
60 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
96 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
30 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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1answer
13 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
21 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
44 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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22 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
30 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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73 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 ...
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1answer
49 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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40 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
95 views

Basic question about chirp signal

Suppose I generate chirp signal with the following python code: ...
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1answer
77 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 ...
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2answers
99 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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38 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
77 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
64 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
69 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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29 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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51 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
49 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 ...
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1answer
71 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
108 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 ...
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1answer
82 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 ...
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1answer
139 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
378 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 ...
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19 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 ...
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1answer
65 views

Sub pixel shift causes weird results

I am trying to shift an image on a subpixel level, with the method described here: ...
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1answer
59 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 ...
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1answer
34 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 ...
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1answer
69 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: ...
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1answer
37 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 ...
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39 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) ...
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43 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 ...
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1answer
493 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 ...
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1answer
146 views

Butterworth filter in python

I'm trying to use a Butterworth filter in Python as described in this thread with these functions: ...
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1answer
44 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 $X$,$Y$ ...
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70 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 ...
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107 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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131 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 ...
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0answers
120 views

GCC-PHAT cross correlation

I am trying to implement GCC-PHAT in python. The approach is similar to the following two links: link1 and link2 It seems the only difference between GCC-PHAT and normal cross-correlation using FFT ...
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3answers
69 views

float image to integer type image

I have a multispectral satellite image and I would like to "transform" each of the image bands into one with integer values. For example to stretch? the image between 0 and 255. Not sure how to ...
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1answer
78 views

correct for shift from butterworth filter?

I have implemented a python butterworth filter but it seems to shift the data a lot, the x location of my data is very important to me for my analysis. Is there a way to correct for this shift ...
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2answers
83 views

How to change the start point of resampling process?

I'm trying to resample a digital communication signal in SciPy or Matlab. Suppose the signal was sampled at 3 samples per second, and I want to resample it to 2 samples per second, the thing is I also ...
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0answers
121 views

Using Python with scipy.signal firwin, how do I know how many taps/coefficients should be used?

I need to alter an FIR filter which I know very little about. I have a signal which need to be altered, and looking at a Python script used for this task, I see that it uses Scipy's signal library, ...
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1answer
64 views

Advice on filtering a CW signal for processing

This question is related to my other recent questions. In the last question, I learned that I should filter about 4 * WPM (words per minute) around the carrier frequency if I want to recover Morse ...
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1answer
76 views

How to decode Morse code (CW)

I have two related questions on this topic. First, about how wide should the filter be around the carrier frequency? What is used to determine this? Second, in Python, I must use 'numtaps' when ...
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1answer
335 views

python; audio; detecting silence in audio signal

I have real-time audio application written in python, and I have question about detecting silence. What's the most efficient way to distinguish silence from non-silence, in an input audio signal? By ...
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2answers
54 views

Color artifacts in Fourier transformed image

I am working with images and Fourier transforms. I am trying to understand what might be causing some artifacts in my output image. I am starting with a 512x512, RGB image of Lenna. I FFT the ...