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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Identifying a signal by its power spectrum

Background: There is a method in optics for determining the electric field of light (both intensity and phase) via a three step process: Add a known phase shift to the light (called the "...
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78 views

When if an FFT more efficient than Goertzel?

Given a block, $x[n]$, of M samples. Calculating abs(fft(x)).^2 returns the power spectrum of that block through the use of a $M$-point FFT. I can calculate the same using Goertzel's algorithm. At ...
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Non Radix-2 FFT Algorithms

I have 25,200 samples of data. My bandwidth is 12.6KHz and my Fs is 1.26MHz, I want to plot an Amplitude-Frequency Spectrum to display up to 100 different signals, that's on purpose (12,600 * 100 = 1,...
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60 views

Dividing a data set into segments with consistent inner behavior, using segmentation algorithms and metrics for consistency

Context of the problem: I have signal data which was recorded in a software system and which shows the runtime of multiple processes over time. In total there are more than 900 processes each having ...
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Selecting subset of sequences so their sum has minimum variance?

I have a set of N real sequences and need to pick K sequences (with no replacement) such that their sum has the minimum variance. E.g. I have N=3 real sequences of length 5: ...
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Efficient Method to match vector time series where the vector entries may not line up

Asking here because I couldn’t find or didn’t have the right words to search for the answers online. Also sorry for no examples—gotta maintain my NDA for work. I have two N-dimensional vector time ...
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Active noise control in LabVIEW using cRIO (FPGA and real-time module)

Has anyone tried to implement the example code in LabVIEW for active noise control usin the my CRIO controller? I have an experimental setup of two microphones (primary and error microphone) and two ...
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The power of signal processing when faced with hardware constraints

I am currently studying interferometry, but I have only just begun studying signal processing. I want to better understand the effect signal processing can have in maximising signal detection from ...
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Processing accelerometer and gyroscope data

I'm working on an instrumented headform to measure linear and rotation acceleration of the on impact, for which I'm using ADXL377 accelerometer and ICM-20649 angular rate sensor. What kind of ...
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84 views

Is there any deterministic downsampling algorithm for audio?

I was trying to use the scipy.decimate function provided in the library, but I had a question - I want a pre-processing algorithm to downsample audio in such a way ...
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Multi-statelevel detection

I'm trying to develop an automated state-detection algorithm, basically expanding on MatLab's "statelevels" function to multiple (i.e. 3+) states, however I've hit a brick wall in trying to ...
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Identify which of the three signals is closest to a sinusoidal curve

I have some acceleration values from a sensor. These values are reported as x, y and z components of the acceleration. As can be seen in the attached figure, it is clear that the z signal has a clear ...
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ANSI S1.11.2004 Octave-Band Filter implementation

I am trying to implement some code to firstly generate an Octave-Band and Fractional-Octave Band filter. I have used MATLAB's octaveFilter method to generate compliant Class-1 and Class-0, 1/1 and 1/...
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79 views

Digital integrator

I have been implementing a control software where I need to calculate a magnetic flux based on the measurement of the phase voltages of a three phase grid (basically three sinewaves) according to the ...
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What is the RFFT and iRFFT complexity?

What is the RFFT and iRFFT complexity for 1D and 2D? Here is some starting point. 1D RFFT The FFT is $\mathcal{O}(N\log N)$ RFFT computes $N//2 + 1$ frequencies instead of $N$. Thus, RFFT is $\...
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Removing feature matched outliers within same image using RANSAC

I'm a student working on a copy move forgery detection algorithm. I have a forged image. By far I have, Found keypoints and descriptors from the image Matched the descriptors using 3 Nearest ...
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Dynamic sampling of thermal images

My master’s dissertation subject is to analyze and implement an algorithm that would sample (store) thermal images from camera with different frequency rates to optimize database size and processing ...
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How do I implement a footstep recognition algorithm? One that recognizes the start and end points of each footstep?

I have some time series data captured from a person's footsteps/strides (specifically, a person on rollerblades). It came from an IMU sensor placed on a person's boot. Each data point captures ...
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Bilinear Interpolation Algorithm for up-sampling 2D images

In keras it is possible to use UpSampling2D layer to up-sample an image. You can use Bilinear Interpolation. Given an image ${h\times w}$ it is possible to increase its size in ${h*k\times w*l}$, ...
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What is the input dimension for LMS update algorithm

I just realized this forum existed, posted my question on the wrong forum. Sorry about the formatting, please don't hesitate to ask if any part of this post is unclear. This is my first post. I'm ...
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How do you map indices to twiddle factors in FFT

I am kinda lost on how to map my indices for each stage to my look up array of precomputed twiddle factors. For an $N=8$ point FFT i have $N/2$ twiddle factors in total: ${ [0] = W_8^0, [1] = W_8^1, [...
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image processing, edge enhancement

*Hello I used k mean method to detect edges and that’s my results as shown in the pic but I want to get more accurate results so I need to enhance my edge detection more what methods would you suggest ...
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Effectively extracting “real” data from a noisy dataset

This question was originally posed to Math SE. It was suggested that DSP SE would be more suitable. Background & Motivation: I have three lists of timestamps (UNIX timestamps, plus a subsecond ...
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FFT seems more accurate than MUSIC algorithm?

I created a signal with two sinusoids and added increasing amounts of random noise to it. The results of running the FFT and MUSIC on this signal are shown in the image below. Ignoring the fact that ...
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How can I implement a phase detection algorithm with my amplitude detection?

I have been recently working on a signal detection problem in Matlab. At the minute I am detecting signals based on their amplitude, using an m-of-n detector. I am interested in improving the false ...
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If a function has slowly varying amplitude and phase what is the bandwidth of the amplitude and phase individually?

I am dealing with time histories that are narrow band with slowly varying amplitude and phase. I wish to extract the amplitude and phase but there is noise on the time history. An example of the type ...
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Why use both packet detection and symbol timing offset in WLAN 802.11?

In IEEE 802.11 Wlan, at the receiver side, we first use packets detection algorithm to detect the start of the packets, and then uses fine symbol timing estimation algorithm to find the start of the ...
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Why do we need DFT when we already have DTFT?

We already have DTFT so why do we need DFT? Please don't write DTFT is used for discrete, aperiodic signal which transfers in the frequency domain to periodic and continuous, but in DFT is discrete ...
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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 ...
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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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103 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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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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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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105 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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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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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 ...
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1answer
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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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1answer
172 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
129 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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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 ...
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118 views

Upsampling implementation

I have problem with upsampling implementation in the following way: My code: ...
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705 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 ...
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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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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 ...
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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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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 ...
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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 ...
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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 ...
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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 ...
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How CDMA receiver extract it's corresponding data from the receiving modulated & superposition-ed signal?

I have difficulty understanding CDMA. I have read all those PN/walsh code things, and understand orthogonality very well. But none of the resources I found demonstrate how a receiver end extract ...

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