# 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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I've recently asked a similar question aiming at the same problem on Math.SE, for which I've set a bounty. Problem. I have a radio calibration transmitter with known fixed location \langle t_x, t_y, ... 0 votes 0 answers 8 views ### image preprocessing(filtering) : before or after undistortion and stereo rectification I'm currently working on a stereo visual-slam program (using OpenCV). After I get the images, there are 2 preprocessing steps to be done : A) Undistort the images + stereo rectification B) Some ... 0 votes 0 answers 11 views ### Problem with "Topological Structural Analysis of Digitized Binary Images by Border Following" by Suzuki Abe I have a Problem with the Paper "Topological Structural Analysis of Digitized Binary Images by Border Following" by Suzuki and Abe. In the Chapter "Appendix I: The Formal Description of ... 0 votes 0 answers 9 views ### Finding rectangle corners by using point cloud I have a rectangle in the 3D scene, which I know its width and height. It is placed in the 3D scene like the image below. I can manually select all points on the rectangle by mouse click. Given the ... 11 votes 4 answers 14k views ### Programming a Vocoder I'm want to program my own vocoder synthesizer like "Songify" but I can't find a simple of vocoder algorithm. Maybe you can explain or tell where to look for information on how vocoder works. 5 votes 1 answer 11k views ### Understanding FFT: FFT size and bins I'm trying to implement an FFT to understand how it works. I'm using a random sound file (so i can't control the size of the signal), with a sampling frequency of 44,1Khz. I'm using this library ... 0 votes 1 answer 1k 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 ... 0 votes 1 answer 57 views ### convert from binary to hexadecimal according to the algorithm "keeloq" Good afternoon. I have the key to my gate. I received its recording in the form of a PWM pulse train. Instead, I converted the impulses into binary code. Now I should get the hex numbers but it doesn'... 11 votes 6 answers 7k views ### Kalman Filter - Implementation, Parameters and Tuning First of all, this is the first time I try to make a Kalman filter. I earlier posted the follwoing question Filter out noise and variations from speed values on StackOverflow which describes the ... 0 votes 1 answer 35 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 ... -1 votes 1 answer 181 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.... 3 votes 1 answer 349 views ### How to get a Standard Deviation weighted average in image? Now I'm trying to implement a SDLWGW algorithm by the MATLAB. currently I'm referencing from Automatic White Balancing Using Luminance Component and Standard Deviation of RGB Components The problem is ... 5 votes 2 answers 2k views ### Pisarenko Harmonic Decomposition I'm attempting to code Pisarenko's method for some time-series data that I have. I've had a look at a couple of papers, which explain in detail the theory behind it, but I'm having some trouble ... 0 votes 1 answer 589 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-... 1 vote 2 answers 55 views ### Which of an array's contiguous subarrays is an algorithm best applied to? A functionf$accepts two equally-long arrays$A$and$B$as input, and returns a real number$s$such that the root mean square of$A-sB$is minimal. I'm hoping to come up with a better-than-brute-... 0 votes 0 answers 31 views ### How to decided the score threshold in speaker recognition? I am new to speaker recognition and now starting from the GMM-UBM algorithm. Say I have a pre-trained UBM and speech from target speakers ... 1 vote 1 answer 193 views ### Separation of signals without loss of information about the signals themselves There is a signal that contains: Rectangular pulses on frequency of 1 kHz Rectangular pulses on frequency of 1.4 kHz Other noises. Required: Separate 1kHz pulses from everything else and measure ... -1 votes 1 answer 150 views ### How to automatically identify a surge in a periodic signal Say I have a periodic signal i.e. Sine wave, which sometimes can have spikes that are 100% larger than the peak value. These spikes can be periodic as well. I'm trying to find an algorithm that could ... 0 votes 1 answer 48 views ### What difference AoA algorithm between 4x4 URA and 12 elements square shaped? I'm reading a paper from Lund University. They show the measurement and compare the accuracy of 3 types of arrays. The interest and question I got are two types, 4x4 URA and 12 elements square-shaped. ... 1 vote 1 answer 118 views ### How do I implement a footstep recognition algorithm? One that recognizes the start and end points of each footstep? I have some time series data captured from a person's footsteps/strides (specifically, a person on rollerblades). It came from an IMU sensor placed on a person's boot. Each data point captures ... -1 votes 1 answer 174 views ### Approximating a Gaussian Process Suppose that$\theta_t$is an exogenous variable with known Gaussian process. Next, suppose that for any index$i\in [0,1]$, $$a_{i,t} = (1-\beta)\mathbb E[\theta_t|\mathcal I_{i,t}]+\beta \mathbb E[... 14 votes 2 answers 3k views ### What Is the Algorithm Behind Photoshop's "Black and White" Adjustment Layer? Can someone explain the algorithm behind the "Black and White" adjustment layer in photoshop? I have to reproduce it using C++ for an application that emphasizes non-red/magenta(ish) pixels ... 2 votes 1 answer 2k views ### Are there any signal processing libraries that implement TD-PSOLA? For such a popular and old algorithm, I've had surprisingly little luck finding implementations. I've got it working in MATLAB, but am curious if any other languages have libraries containing it (... 1 vote 0 answers 54 views ### Why some implementation of Wavelet transform use reconstruction filter instead of decomposition filter? I'm using MODWT (Maximal Overlap DWT) to extract features from a signal. Matlab implementation is using reconstruction filter instead of decomposition filter. In the first level of modwt decomposition,... 2 votes 2 answers 93 views ### Are there any efficient algorithm to detect circular shape of arbitrary size in an image? I have images that are 1278 by 1024. They are pictures of a certain product that is rectangular in shape and are about 25mm by 20mm. As a part of a quality inspection process using computer vision, ... 0 votes 1 answer 163 views ### Evaluation of incremental sensor Evaluating a volume flow incremental sensor does not deliver expected results. The pump of which the volume flow is to be measured has a hand-calculated flow rate of$$Q = \dfrac{n}{ 60 \;\mathrm{s/... 0 votes 0 answers 20 views ### Automatic frequency extraction from periodogram I'm measuring periodograms from quasiperiodic orbits in a 2D Hamiltonian system. I'm using the Welch filter, and a equally spaced time grid (+ simple FFT), see example figure below (bottom: signal - ... 0 votes 1 answer 3k 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: ... -1 votes 1 answer 63 views ### Convolution of a discrete continuous function for reconstruction From chapter 9 page 198 of https://github.com/t4world/Computer-Graphics/blob/master/Fundamentals-of-Computer-Graphics-Fourth-Edition.pdf I am confused as to what this book's description is saying ... 8 votes 2 answers 1k 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 votes 0 answers 21 views ### What is a good algorithm for filtering data from a sensor that occasionally malfunctioned? I was in a lab and recorded some data from 2 pressure sensors. One worked perfectly (red line), the other one would send random data occasionally (blue line.) All of my values are supposed to be ... 0 votes 0 answers 52 views ### How is the 'difference' of two audio tracks best computed, in order to maximise instrument isolation? I'm hoping to improve the results of a simple application I've been working on, which aims to isolate as fully as possible the electric guitar heard (along with drums/bass/vocals) on a single track of ... 0 votes 0 answers 22 views ### Algorithm for unique speaker detection I have some speech data and I would like to know approximately how many unique speakers are there in it. A very crude way is to do it manually by randomly selecting a small sample set and taking the ... 3 votes 2 answers 4k views ### Why do we need DFT when we already have DTFT/DTFS? 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 ... 1 vote 3 answers 715 views ### range-doppler map to range-velocity map conversion UPDATE 2.0 I think I've managed to produce the correct range-velocity map. I'm struggling with analytically calculating the range which I expect to see on the range-velocity map. Could someone please ... 24 votes 3 answers 11k views ### Fastest Algorithm for Distance Transform I am looking for the fastest available algorithm for distance transform. According to Image Processing Learning Resources - HIPR 2 (HYPERMEDIA IMAGE PROCESSING REFERENCE) - Morphology - Distance ... 1 vote 0 answers 1k views ### Radix-8 butterfly with Winograd and Cooley-Tukey algorithm I saw the Winograd radix-8 kernel algorithm below, shown in the image. Comparing to the mathematical formula of Cooley-Tukey, there is a multiplication by$\cos$and$\sin(\pi/8)$, which can't be ... 1 vote 0 answers 35 views ### Do CQT, FFT, and NNLS provide different "perspectives" on the original signal? From a bird's-eye perspective, do CQT, FFT, and NNLS algorithms provide different "perspectives" on the original signal? Does each preference some features of the original signal? I'm using ... 0 votes 1 answer 39 views ### 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 "... 1 vote 1 answer 133 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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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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### 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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### 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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### 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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### Why Is the Result of the Convolution of a Row and a Column a Two Dimensional Matrix?

I'm trying to understand a book chapter on "Algorithms For Efficient Computation of Convolution" (Also on Doc Droid or Scribd) and I know that when calculating the convolution of an image represented ...
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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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### How to Use the Walsh Hadamard Transform to Filter 24 bit RGB Color Values in a Localized Spatial Region?

After reading this Signal processing Stack Exchange article tonight, What Is the Walsh Hadamard Transform? How Could One Use It in Image Processing?, I became interested in applying the Walsh-Hadamard ...
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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 ...