# 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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### implement gradient descent with sparsification algorithm

I am trying to implement the algorithm in this paper for finding a sparse vector x that minimizes the square error $\lVert y − \Phi x\rVert_2^2$ where $\Phi$ need to satisfy the restricted isometry ...
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### Optimized ANSI C libraries for DSP

I am new to DSP. Are there good open source ANSI C implementations of DSP algorithms? MATLAB is great at prototyping but once we move to coding in C, it takes time and we end up making too many ...
1 vote
49 views

### Is fft always the best choice?

I hope this is the right place to ask this question since it is partially a note which might help others. Until recently, I always used the fft-algorithm ...
1 vote
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### Steering Vectors and Bluetooth Low Energy for computing Angle of Arrival

I am new to signal processing, but I have background in mathematics. I am trying to use Bluetooth Low Energy (BLE) on three mobile devices, where one device is being tracked and the other two act as ...
284 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 ...
3k views

### Books/resources for implementing various mathematical functions in fixed point arithmetic for DSP purposes

I'm looking for books or resources that cover the following in detail: implementing mathematical functions (e.g., logarithm, exponential, sine, cosine, inverse) in fixed point arithmetic for DSP ...
9k 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 multiplications per output sample. And by &...
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### 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 ...
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### What is the name of a low-pass filter that tracks rate of change?

When applying a low-pass filter to a constantly changing signal, there will be a lag between the actual value and the filtered value. For example, if f(x) = x, the ...
409 views

### 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 ...
71 views

### Cfar Algorithm Implementation

I am trying to implementation Cfar algorithm to our radar signal processing algorithm. I obtained some output but I want to be sure that is right. Cfar algorithm's output below like, I'm interpreting ...
713 views

### One Too Many Non-Zero Eigenvalues in MUSIC DF Algorithm

I'm working on simulating the MUSIC algorithm in MATLAB to determine the azimuth angle of arrival of a simulated signal. My virtual antenna array consists of 4 antennas arranged in a plane. While I ...
44 views

### How to detect known audio samples within a stream of audio

If I've got a bunch of short .wav files, 16 bit linear pcm, and an incoming stream of audio that's been run through a voice codec (g.722, g.711, or others) and then converted back to pcm, what's the ...
109 views

### Which is faster: image segmentation or line detection?

Some papers use image segmentation techniques and others use edge detection. I need to know which one is faster. update: I need to do semantic segmentation for outdoor sense and the data is optical ...
1k views

### HOG descriptor algorithm

I would like to implement a HOG descriptor in C++. I found an implementation of this code in Open Pattern Recognition Project - Histograms of Oriented Gradients (HOG) Feature Extraction. An extract of ...
1 vote
201 views

### How to use MUltiple SIgnal Classification (MUSIC) algorithm to detect the wavenumber of a received signal at array of sensors?

I am working on analyzing data obtained from Fiber Optic - Distributed Acoustic Sensor (DAS) to estimate the properties of acoustic waves that impinge FO cable, such as velocity of acoustic waves. FO-...
3k views

### Estimate Sine Frequency under White Noise — simple and effective method

Given a sinusoidal signal in white noise, how can one efficiently determine its frequency?
714 views

### 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 ...
298 views

### What is the equation I can use to create the inverse expoential graph?

I am seeking an equation I can apply to provide a score based on a measurable ability rating. It would be great to understand how the equation works so I can alter the curvature of this flexibly based ...
1 vote
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### Measure of how well sounds fit together in a composition

Are there any approaches to gauge how well a sound may sit together with other sounds in a mix? I’m thinking about something similar to picking instruments that might go well together in a band. ...
6k views

### 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 ...
116 views

### Algorithm for finding best matching sin wave to input signal

Question Suppose I take a signal $y(t) = \cos(2\pi \cdot 4.1t + 2)$ and I sample it uniformly up to 2 seconds. Given only these time samples, how would I design an algorithm that finds the pair of ...
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### Is there an algorithm to compute the phase for a single frequecy?

If you have a function $f(t)=A \cdot \sin(\omega t+\phi)$, and reference sin wave $\sin(\omega x)$ what would be a fast algorithm to compute $\phi$? I was looking at Goertzel algorithm, but it doesn'...
1 vote
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### How should I go about calculating sines or cosines without the errors introduced solely by the transcendence of pi?

This may be irrelevant for many people but I'm asking this question because I don't need to do these things in real time, I don't care if modifying a 1-minute sound recording takes 5 minutes to ...
171 views

### How to detect signal in spectrum without empirical data

Let's say, I have got a spectrum of a signal with noise using fft: For a human it's pretty obvious that there is a signal with a frequency of about 51Hz. But what is the mathematical apparatus behind ...
1 vote
754 views

### 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 ...
194 views

### Matching 2 Undirected Weighted Graph in MATLAB

Consider 2 undirected weighted graph as shown in figure. Consider first graph as $G_1$ and second graph as $G_2$. Graph $G_1$ consist of vertices $V=\{F_1,F_2,F_3,F_4,F_5\}$ and graph $G_2$ consist of ...
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### How to Reduce the Overfitting of a Linear Classifier

I am working in linear classification such as $$y=ax+b.$$ where $x=[x_1...x_n]$. But the method has weakness that is overfitting problem. Could you suggest to me one method or one way to reduce ...
183 views

### MUltiple SIgnal Classification (MUSIC) for Frequency Estimation

I am trying to use MUSIC algorithm to detect individual frequencies of an incident signal. I read the original paper and some interesting books that explain the algorithm. I used the following ...
302 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 ...
8k views

### Using the Kalman filter given acceleration to estimate position and velocity

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 acceleration to read this data, and as confirmed by ...
80 views

### Ways to parallelize Sifting in EMD (Empirical Mode Decomposition)

Sifting process, which is recursive in nature, is used in EMD (Empirical Mode Decomposition) to decompose the signal (x(t)) into Intrinsic Mode Functions (IMFs) and residue, which is a monotonic ...
168 views

### MUSIC Algorithm for 2D Power Spectrum

I am trying to use Frequency-wavenumber analysis for estimating speed of sound using two-dimensional data obtained via channel of arrays. The traditional technique is to use FFT to transform the data ...
22 views

### Model validation- comparing signals

Let's say I am trying to validate a model. I have a signal from measurement and a signal from the simulation of the model. Simulation was done with the same initial and boundary conditions as ...
1 vote
167 views

### DSP function used by musical distortion plugins

In short: what kind of mathematical function was applied to this sine WAVE? I am trying to implement my own distortion plugins. Amongst other things I have read several chapters of Will Pirkle's book (...
780 views

### How to measure aliasing?

Aliasing is bad, and we want good filters when downsampling. While what qualifies as aliasing is well-defined mathematically, and we can manually design filters with various tradeoffs, how do we ...
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### model of a quasi static block fading channel in MIMO system

can I know what is the model of a quasi static block fading channel in a MIMO system, in function of angle of departure and arrival?
175 views

### How do I do a point response FMCW SAR simulation?

I am trying to simulate and focus the point response for an FMCW stripmap SAR system. I have specified my target coordinates as targets = [100,100,0;400,100,0] and ...
779 views

### Identify abrupt changes in an audio waveform

I have an audio file which was created by substituting multiple speech segments into an original utterance. I want to find the timestamps where such substitutions happened, so I guess that one thing I ...
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### Is there any method to incorporate boundary periodic conditions into the kernel summation over unstructured data points?

Supposing that there are $N$ particles distributed inside a periodic cubic box of volume $V=L^3$, I want to divide the cube into a regular mesh and calculate the following summation at each grid point ...
1 vote
138 views

### Measures of "coincidence"?

Assuming I have two sensor feeds, is there an algorithm that gives an estimate of how likely it is that they point at/derive data from the same scene (possibly from different angles, with different ...
1 vote
1k views

### What are the step by step actions taken in order to convert PDM data to PCM data?

I would like to convert PDM (Pulse Density Modulation) microphone data into PCM (Pulse Code Modulation) data. I understand that ...
1 vote
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### Different kinds of beeps and tones

I have heard many different types of beeps, chimes, and other tones. Audacity allows me to generate simple waveforms like sine waves and square waves, as well as DTMF tones. But I want to generate ...
101 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 ...
113 views

### Finding start point of a curve

I'm currently working on a project where I have to measure the latency of a given system. Below you can see a exemplary image which shows the input pulse (green) and the response (blue). In order to ...
19k 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: Fft....
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 ...