Questions tagged [algorithms]

Algorithm is a method expressed in a finite list of steps of well-defined instructions to process a signal.

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2
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2answers
177 views

Fast Morphological Erosion / Dilation with Variable Window Size

I want to perform the following operation on an image: consider a square window around every pixel, find the maximum value in this window, and replace the central pixel value with this maximum value. ...
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2answers
2k views

Improving Template Matching Algorithm for OpenCV

Car detection using OpenCV I am working on a small personal project where i have to know wether an image shown is a car or not. I am using the basic OpenCV python based template matching. Positive ...
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1answer
16 views

Implementing an L-System conversion from R2 to R1 for symmetric, square matrices

I have been reading for some time about L-Systems, and specifically the Hilbert Space filling curve. I am interested in writing a function to convert upper-triangular matrix coordinates into an ...
0
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1answer
54 views

Wrong values calculating FFT with EEG Bands using Numpy

First of all I have to say I am very new to these matters. I am trying to apply FFT algorithm to some values obtained by EEG bands. I found the following code but I am unable to make it work correctly....
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0answers
25 views

Communicate to user that SNR is too low - Speech procesing

I am working in a project to estimate the signal to noise ratio (SNR) for an automatic speech recognition system in order to generate an alert to the user if the noise is too high in the place where ...
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2answers
2k views

FFT Algorithm: Split Radix vs Radix-4

I wanted to know the difference between split radix and mixed radix algorithm. I also wanted to know what is the difference between radix 2 ,radix 4 and radix 8 FFT
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1answer
274 views

Need Help with Time-Stretching WSOLA Algorithm

I’m having problems implementing time-stretching using the Wave Similarity Overlap Add (WSOLA) algorithm. I got the basic OLA algorithm working first and then added wave alignment using cross-...
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0answers
32 views

DFT algorithm designed for a “sample-by-sample” senario

Suppose I have a system that wants to take an input signal (audio in this case) and wants to output a Discrete Fourier Transform of it in real time (ie every sample). My initial thought is that if you ...
2
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1answer
167 views

How do audiobook players manage to quickly speedup/slowdown playback speed without using more memory?

Many audiobook player apps on Android have a reading speed slider which lets us choose the reading speed e.g. 0.5x 0.75x 1.00x 1.25x 1.50x. This is time-stretching ...
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0answers
27 views

Goertzel filter for non-equidistant sampling

We have a sensor that reports a new value asynchronously only when the value changes. Therefore, we receive samples at arbitrary time stamps. We basically receive value + timestamp of the measurement ...
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1answer
73 views

MUltiple SIgnal Classification (MUSIC) Implementation

I have a linear 4 element antenna array currently in my design, I am able to obtain the I/Q data from each antenna. Now I am trying to implement the MUSIC algorithm to obtain the AoA (Angle of Arrival)...
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3answers
3k views

Measuring Audio Signal Similarities

I have recorded samples of lungs sound (person breath) signals from electronic stethoscope. How can I measure (In percentage) the similarity between two audio signals (lung sound), the general idea is ...
0
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1answer
142 views

Separation of signals without loss of information about the signals themselves

There is a signal that contains: Rectangular pulses on frequency of 1 kHz Rectangular pulses on frequency of 1.4 kHz Other noises. Required: Separate 1kHz pulses from everything else and measure ...
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1answer
51 views

Minimize the Cost Function of Values of Vectors Based on Their Amplitude

I have two vectors $X = [x_1,x_2,x_3,x_4]$; and $Y = [y_1,y_2,y_3,y_4]$; I know that $|x_1|$ = $|y_1|$, and $|x_2|$ = $|y_2|$,... so on. it means the difference is only in the sign. it might be ...
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1answer
151 views

Algorithm that Fills the White Holes Within the Character Image

I have this degraded image : Using paintbucket tool in Paint.NET Windows application, I fill the character image black. My ...
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1answer
73 views

How to automatically identify a surge in a periodic signal

Say I have a periodic signal i.e. Sine wave, which sometimes can have spikes that are 100% larger than the peak value. These spikes can be periodic as well. I'm trying to find an algorithm that could ...
9
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4answers
5k views

Looking for an arcsin algorithm

Does anyone have a simple algorithm for computing a reasonably accurate arcsine? By "simple" I mean some sort of polynomial that requires <= 5 multiplies per output sample. And by "reasonably ...
0
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1answer
149 views

Approximating a Gaussian Process

Suppose that $\theta_t$ is an exogenous variable with known Gaussian process. Next, suppose that for any index $i\in [0,1]$, $$ a_{i,t} = (1-\beta)\mathbb E[\theta_t|\mathcal I_{i,t}]+\beta \mathbb E[...
2
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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 (...
2
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1answer
60 views

Are there any efficient algorithm to detect circular shape of arbitrary size in an image?

I have images that are 1278 by 1024. They are pictures of a certain product that is rectangular in shape and are about 25mm by 20mm. As a part of a quality inspection process using computer vision, ...
0
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1answer
141 views

Evaluation of incremental sensor

Evaluating a volume flow incremental sensor does not deliver expected results. The pump of which the volume flow is to be measured has a hand-calculated flow rate of $$Q = \dfrac{n}{ 60 \;\mathrm{s/...
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1answer
2k views

Recursive systematic convolutional code (RSC) realization in MATLAB

How can I implement $\rm RSC(2,1,2)$ in MATLAB? Can I use convenc function to build RSC? The convenc function has 2 arguments: ...
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2answers
3k views

methods of computing fixed point atan2 on FPGA

I am in need of computing atan2(x,y) on an FPGA with a continuous input/output stream of data. I managed to implement it using unrolled, pipelined CORDIC kernels, ...
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4answers
13k views

Simple and efficient algorithm to detect frequency and phase of a sine signal

I need an algorithm to detect frequency and phase of a pure sine signal. The frequency of the input signal changes between 0 and 100 Hz. The value of the signal gets captured with a frequency of 20 ...
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1answer
65 views

FFT algorithm gives wrong signs on my output numbers

I was told from another stack exchange (stackoverflow and computer science stack exchange) to post here - so hopefully now i can get some help from people who understand the algorithm, but if this is ...
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3answers
13k views

Digital Distortion effect algorithm

I read the DAFX book by Udo Zölzer about the distortion effect at pages 124-125 and it says that suitable simulation of the distortion is given by the function: $$f(x)=\frac{x}{|x|}\left(1-e^{x^2/|x|}...
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0answers
21 views

Is my implementation of Generlized Pencil-of-Function correct?

I have a time-series data that should be of the form $$ f(t) = \sum_nA_n(e^{\alpha_n t}+e^{-\alpha_n(T-t)});\;\alpha_n=\eta_n+i\omega_n;\;i=\sqrt{-1} $$ and I want to find parameters $A_n$, $\eta_n$, ...
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0answers
30 views

Asymmetry In The Mirroring Of An FFT Of A Sinusoidal Signal

I am trying to implement a Cooley-Tukey FFT algorithm in its iterative version. Specifically, I am implementing this Wikipedia pseudocode (please look at the section Data reordering, bit reversal, and ...
2
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1answer
53 views

Clear examples of Fixed Point Algorithm Specification Block Diagram for FPGA Implementer

I have been working on converting a simple, floating point algorithm to fixed point and need to create a block diagram to help the guy who will implement this on an FPGA. As often is the case, the ...
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0answers
21 views

Remove background, keep black characters

I use ID scanner machine (link) to remove the background. The result is the gray image below. It seems that the scanner uses IR to do that. Is there any algorithms to obtain the same result? Thanks in ...
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1answer
64 views

Discrete Wavelet Transform output: coefficients or FIR-filtered signals?

I have a theoretical question about the calculation of the Discrete Wavelet Transform, using MATLAB specifically. According to this video-tutorial on the MATLAB lagorithm: https://it.mathworks.com/...
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1answer
75 views

Algorithm to Count Zeros Outside Unit Circle for FIR Filter

As detailed in this post Can I set a constraint on the first tap of an FIR filter such that its inverse is stable? I show how Cauchy's Argument Principle can be used to easily confirm if an FIR filter ...
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0answers
171 views

Mapping ring asteroids in Elite Dangerous by image processing

In the game Elite Dangerous, which is an online spaceflight-based sandbox game set in a procedurally-generated galaxy, one of the most profitable in-game occupations is mining commodities from ...
0
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1answer
58 views

Upsampling implementation

I have problem with upsampling implementation in the following way: My code: ...
8
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5answers
980 views

Fast & accurate convolution algorithm (like FFT) for high dynamic range?

It seems that FFT-based convolution suffers from limited floating-point resolution due to evaluating everything around the roots of unity, as you can see in the $10^{14}$-factor error in this Python ...
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1answer
60 views

What is the difference between time complexity and sample complexity?

What is the the difference between time complexity and sample complexity in the context of algorithm development? I'm currently studying the sparse Fourier transform and this idea of sample ...
10
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1answer
1k views

How do I implement an adaptive thresholding algorithm for underwater sonar

I want to implement an adaptive thresholding algorithm in MATLAB for filtering data received by an underwater sonar receiver. The data received has an interactive noise component resulting from ...
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0answers
32 views

What is the technical term to join two signals with different phases?

there is a name for this: If I have two signals with a discontinuity, arrange the phases of one signal to fit the other and not see the discontinuity.
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0answers
38 views

Why does the griffin lim algorithm work?

the griffin lim algorithm works to reconstruct audio from a magnitude spectrogram, but i don't understand how reusing the same spectrogram every iteration with noise can produce decent sound How from ...
3
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1answer
4k views

Using the Kalman filter given acceleration to estimate position and velocity

Note : port from this post, until fully merged. I am reading data from an accelerometer. I want to use this data to estimate velocity and position. Originally, I performed a double integration of ...
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0answers
13 views

Question regarding the implementation of the guided random walks algorithm

I'm working on the implementation of the paper: Segmentation by retrieval with guided random walks: Application to left ventricle segmentation in MRI. I tried to modify the weights functions mentioned ...
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0answers
64 views

Is there a FFT algorithm which is both in-place and constant geometry?

I work in crypto where the NTT (Number Theoretical Transform) which is just a FFT in finite fields is used. I wanted to know if there exists an implementation of the FFT which is both in-place and ...
11
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2answers
2k views

What Is the Algorithm Behind Photoshop's “Black and White” Adjustment Layer?

Can someone explain the algorithm behind the "Black and White" adjustment layer in photoshop? I have to reproduce it using C++ for an application that emphasizes non-red/magenta(ish) pixels from an ...
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2answers
176 views

High / Low Pass Filters from Zero

I everyone, I'm a computer scientist but not from the signal processing community. I want to implement a real time digital low pass filter (to begin with) for a sound processing application. I've ...
5
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2answers
992 views

Kernel Convolution in Frequency Domain - Cyclic Padding

I don't know whether this is the right place to post this, but I suppose it is. I know that frequency multiplication = circular convolution in time space for discrete signals (vectors). I also know ...
0
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1answer
334 views

Algorithm to convert a GeoTIFF file to PNG image format

I have a bunch of GeoTIFF files that I am processing into a TFrecords format for machine learning. Now I can't put tiffs directly into a TFRecords format and so I ...
0
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1answer
170 views

Algorithm/Code for finding surface shape of an image?

Is it possible to find the surface shape of an image as mentioned in the reference question ? If I find the unknowns of the equation , then what should be my next step in determining the shape of the ...
0
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1answer
59 views

RF signal identification algorithms

There exist many, many analog and digital data transmission protocols. It is often difficult to tell which mode one listens to and tedious to do for many signals. In Ham Radio, a Reed-Solomon ...
1
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1answer
48 views

How to compute an old style shore line drawing?

I wish to represent a shore line, old-style, as in the following image (city on the left, water on the right): UPDATE: new image for another example of what I'm after, namely the thin lines (given ...
1
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1answer
102 views

What language or framework would you use to develop and test natively algorithms meant to be ported on an embedded hardware later?

I am trying to find a nice clean solution to this problem since some days now, and couldn't make myself to stick to a solution. I need to develop some stream and block processing for audio, including ...

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