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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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 ...
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Is sparsity induced penalty in source separation "Entrywise matrix norms"?
I am reading this paper where they introduce norm penalties for source separation. In table 1, the $\log/ l_1$ type is $\sum_{g} log(\epsilon + \lVert H_{g} \rVert_1)$. I wonder this $\lVert H_{g} \...
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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: Fft....
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Method for finding the best non-increasing approximation function of a given signal
I have a discrete-time signal (with noise) and I want to determine the best non-increasing function that represents it.
Of course it would be useful if the obtained function were defined in terms of ...
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Doubts on LMS derivation
I have been trying to follow the Least Mean Square(LMS) algorithm derivation given by Wikipedia here and have the following questions.
Here I expected $y(n)$ is to be computed by convolving $x(n)$ ...
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Computational Complexity of Polyphase Resampling
does someone know the approximate computational complexity of a polyphase resampling algorithm?
I am trying to find a good argument to prefer a polyphase resampling of Scipy over the FFT resampling ...
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Selection of transforms, windows, wavelets for current signal analysis
I am new to this topic but I already read about the propperties of different signal analysis methods. I am stuck with the obvious advantages of FFT, STFT and Wavelet transforms but can't find good ...
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Clustering algorithm [closed]
I am looking for some suggestions regarding clustering.
Lets say
I have 5 subjects (1, 2, 3, 4 and 5)
...
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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[...
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recognize unwanted sounds, noises, and deleting them algorithm
I have a function that I need to use denoise algorithm on.
What I thought is to divide it to smaller parts and then use Fourier Transform on each one of the parts, but I am not sure what to do next.
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Accelerometer to track Potholes
So I am trying to make an application to track potholes in a road. I am using accelerometer readings for that. Assuming that the phone is mounted in a car and our orientation doesn't change. After ...
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How to label sound events in noisy .wav files
I'm trying to find a way of automatically identifying birdsong in phone-recorded sound files (1min long). Currently the algorithm I'm using doesn't label all of the events I want it to. (it is ...
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Finding good feedback coefficients for basic reverb
I'm currently working on some reverb algorithm code for the Gamebody Advance to get a bit of that ambient feeling for the music instead of having plain dull sound. A few challanging restrictions are ...
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Engine for Google / Browsers to detect manipulated images? [closed]
Would it be possible for Google and web browsers to scan images and detect doctored photos?
For example, a web browser could check for abnormal color gradients and signals that indicate if a photo ...
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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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Introduction to fast algorithms for time–frequency analysis
I had preliminary knowledge of digital signal processing from Oppenheim's Discrete-Time Signal Processing and is studying time-frequency analysis now. May someone suggest introductory reference (...
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Combining different Likelihoods - Particle Filter
I am new to particle filters and have a problem when it comes to the weightening (using SIR to be precise).
The problem is that my different state-variables are subject to different noise-...
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Finding notes played in an audio clip
I am working on a program that will be able to tell when a musical note is played in audio and what that note is (ie. guitar or piano). You can assume can assume any audio used for the program will be ...
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Fast way to calculate a few points in convolution?
Say I have two 1000-point sequences. I can compute the entire convolution fairly efficiently using FFTs (keeping in mind that zeroes have to be padded on to avoid doing a circular convolution).
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Filter Implementation
I am rather new to the world of signal processing, and am struggling to understand a fundamental concept: How are filters actually implemented?
I have read a significant portion of this online book, ...
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In filtered back-projection, what does the $z$-axis in the reconstructed cross-sections represent?
The MATLAB code below is used for filtered backprojection (for $x$-rays). In this example program, it reconstructs an image of a simulated checker board, generated by the program. It uses Fourier ...
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Determining the pattern direction of a bitmap image
How can I obtain average direction of the pattern shown in the figure below. It is the direction of the red arrow relative to the yellow (horizontal) line. Any ideas for an approach? I couldn't figure ...
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How can I start learning about pitch detection?
readers.
I'm working on a project where my goal is to implement a pitch-detection algorithm (PDA) in a piece of open-source software.
I have very little knowledge of pitch detection at the moment ...
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Digital filter for sharp impulse in data
I am looking for an algorithm or a filter to remove sharp peaks from my data. I am collecting raw data after every 1 second from an sensor through an ADC. The ADC has an internal FIR filter. I use ...
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Creating a Phantom Sound through 5.1.2 Speaker Configuration
I am trying to use a 5.1.2 speaker configuration (left front, center, right front, left rear, right rear, left front height, right front height and Low-Frequency) to create a phantom sound at a ...
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Name of peak finding algorithm
I've been using this implementation of a peak finding algorithm and it works pretty well. I'm wondering if this particular algorithm has a name?
Python code:
...
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Convex Hull Area in Pixels
I am calculating different attributes for connected regions of the image, with the final goal of classification. One of the attributes I am working with is a sparsity measure, calculated as the ratio ...
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Career Question: As a person who likes math is signal processing a career that's worth it?
I like high level math and I love deep theory based math.
In industry will I use high level math and theory to implement my own algorithms?
I love high level math but I do not love probability (...
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How is Point Spread Function (PSF) related to Image Priors in Blind Deconvolution?
We are researching for our thesis about enhancements in Blind Deconvolution Image Deblurring Algorithm Applied in Image Restoration.
What really is PSF? Is it one kind of image prior? What do these ...
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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 ...
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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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Why isn't the Hartley Transform more widely used?
I was doing a bit of research on FFT and I came across this paper. According to it, computing the Fourier Transform using FHT is significantly faster than other methods, even for complex data. Yet, ...
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What are some of the differences between DFT and FFT that make FFT so fast?
I'm trying to understand FFTs, here's what I have so far:
In order to find the magnitude of frequencies in a waveform, one must probe for them by multiplying the wave by the frequency they are ...
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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 (...
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How to triangulate 2 sources on a 2d plane formed by 4 sensors?
I have 4 sensors capturing signal data. Signal distribution speed is constant and known. I have sensors positions in 3d space.
Also, I have an amplitude/frequency decomposition for data received by ...
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Dot or point pattern recognition for Braille Paper
we are very new to image processing field.
We are gonna do a study about braille to text conversion, by the way braille is a method of writing for blind.
!(https://fryemuseum.org/images/...
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Video stabilization using Lucas-Kanade method
I got an assignment in a video processing course - to stabilize a video using the Lucas-Kanade method. Assuming the matlab code I wrote for performing LK on 2 images works (i.e, I can get the optical ...
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Frequency identification as a convex problem
Suppose I have two time series, $x(t)$ and $y(t)$: $x$ is the output of a sine wave generator, and $y$ is the generator's frequency setting. Given a training set of $(x, y)$ pairs, Is it possible to ...
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Need help implementing DCT Type 4 algorithm
I'm trying to implement Algorithm 2 from this paper:
Xuancheng Shao and Steven G. Johnson: Type-IV DCT, DST, and MDCT algorithms
with reduced numbers of arithmetic operations, https://arxiv.org/...
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FFT starting at zero
signal processing is not my domain of expertise , but I need to make use of it, to do an HRV analysis. These are steps I do starting from my raw ECG signal.
ECG signal -> RR peak detection -> find RR ...
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FFT subset output yields computational efficiency
The traditional FFT gives $N=2^k$ outputs for $N=2^k$ inputs (generally complex.) The time effort is $O(N \cdot \log(N))$. If all I want is a compact subset of $M \ll N$ output frequency points, is ...
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Formulating a function on Matlab for the Shannon interpolation formula
I am trying to formulate an algorithm for applying to Shannon interpolation formula to the discrete signal
$$x[n]=\frac{c^2}{4}\int\limits_{0}^{n T}y\left(\tfrac{c}{2}s\right)\,ds,$$
where $c$ is ...
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Understanding equal power crossfades
I'm trying to implement an equal power crossfade between two uncorrelated signals ($A$ and $B$). From what I understand I need to setup the crossfade in the following way
Come up with a function $f(x)...
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Help understanding constant q output
I'm trying to visualise and understand the output of constant q transform. Based on my experience with FFT and the articles I've read so far, I would expect that each output bin would represent one ...
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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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How to get the values for C1 and C2 in Chan-Vese Model?
This question will consider the widely accepted segmentation algorithm of Chan-Vese, given in the following publications:
T.F. Chan, L.A. Vese, An active contour model without edges, Lecture
...
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Algorithm for 1d spline interpolation suitable for 8 bit microcontroler
What is a concise, fast, down to earth algorithm for doing (or closely approximating) spline interpolation on a 1d continuous stream of data?
(Edit1: The paragraph below equates to saying "the ...
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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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DFT algorithm for FPGA without phase
For my FPGA programming lab final project, I want to implement an audio spectrum analyzer. Since I won't be recreating any signals, I only need the frequency magnitude, and not the phase. I'm hoping ...
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Trying to write a signal "unsmoothing" algorithm
Up front: I'm just a hobbyist, and I know zero about signal processing; I'm trying to write a simple(?) javascript algorithm and hoping I don't need a PhD in DSP to make progress on it.
I have an ...
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