# All Questions

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### Transforming FFT to Detect Baud Rate

I've seen in practice taking an FFT of a signal, then transforming it by the 2nd, 4th, etc. power (depending on signal type) to determine the baud rate. I'm trying to implement this in my code, but am ...
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### Is there a better Fourier Transform algorithm to use in Image recognition

I have been trying to use the Fourier transform in recognizing images of the same size 200X400. I have tried many different ways to do that such as: 1 - performing the Fourier on the full image and ...
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### Square signal: from a period histogram to a frequency analysis

I have a dataset of square waves (with periods slightly varying from the nominal one) and I read the times between edges with a PIC microcontroler, so I can obtain a histogram of periods. The data ...
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### Claim: Given sampling time T, the hold operator is approximated at low frequency by a time delay of T/2

Can someone verify this statement? The hold operator is assumed to be a zero order hold Then the laplace transform of this hold operator has a well known form $(1-e^{-sT})/s$ Let w approach 0, we ...
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### Find impulse response and frequency response through given filter

I cannot find anything truly helpful in my book, and I find mostly theoretical answers and not practical. So I am posting the exact exercise I want to solve, and through it I hope I'll work some ...
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I am trying to wrap my head around the original wavelet shrinkage papers of Donoho and others from the mid-90s. There are a couple of curious things that confuse me, and I'd appreciate some input: ...
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### Signal Sampling

I am new in this field (junior year) and I have a question may a little lazy for the majority of the forum. I have a speech signal $x(t)=0.4\cos(100πt)+0.3\cos(1800πt)+0.2\cos(980πt)$ and I know ...
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### Combine multiple FFT

I have been acquiring data through ADC and into memory, the input signal are square waves that step down in frequency as time goes by. Due to memory, I have a fixed maximum number of samples per FFT. ...
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### How I can optimize the DFT become the FFT?

As title, I am trying to understand fast Fourier transform, but I have a little trouble, that is: The DFT said that we must multiply the matrix 2n x 2n with ...
30 views

### Velocity estimation knowing acceleration and displacement from measurements using Kalman filter

I am having a hard time in trying to use a Kalman filter to obtain velocity from acceleration and position measurements. I think the main reason is that I am not familiar with Kalman filters (I had ...
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### regarding autocorrelation and derivation of original signal

$$r_x(t)=\begin{cases} 2-2t ,& 0 \le t \le 1\\ 2+2t ,& -1 \le t \le 0 \end{cases}$$ So how do I get original $x(t)$ from this? I tried integrating the equations, and the value I got was ...
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### What is the ideal type of barcode for paper tickets?

I can use the following type of barcodes in my project: Code 39 Code 128 QR Code Data Matrix PDF-417 They will be printed with standard office printers and with boca printers. It should also be ...
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### Discrete or continuous Kalman filter?

I have position and acceleration measurements and I would like to apply a Kalman filter to estimate the velocity of the system. I am not sure yet about how to procede, but I will check the already ...
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### Determine Frequency Resolution samples

Can someone tell me if the way I solved this problem is right? Suppose I have a signal $X_a(t)= 0.5cos(700πt)+0.6cos(720πt)+0.1cos(780πt)$ where $F_s=8000Hz$ I want to determine the minimum samples ...
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### Energy calculation in frequency domain

I was just wondering... The formula I learned to calculate the energy of the signal is expressed in the time domain: $E_x^{\text{time}} = \sum_{n=-\infty}^{\infty} |x[n]|^2$ Then, what does the ...
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### Interact with the brain

I am purely looking for some advice, and, may be some on line academic reading into the subject, whether it's been proven or whether it's just a hypothesis I still want to investigate it. So far: I ...
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### Deriviation of the “Twiddle Sum” property

I can't seem to understand how to derive the "twiddle sum" property: $$\sum_{n=0}^{N-1}W_{N}^{kn}=N \ \delta[k\bmod N]$$ where $$W_{N} \triangleq e^{\frac{j 2 \pi }{N}}$$ and  \delta[n] ...
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### How can I find this image's end points using morphological operations

I'm trying to solve a question that practises the concepts behind morphological operations. Given the following image, how can I produce a new image with only the original image's end points. Input ...
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### Implementing capons spectral estimator in python

I am trying to implement capons high resolution frequency-wavenumber spectral estimator (mvdr) for use with data from an isotropic array. My results were unstable so I use diagonal loading. I am a bit ...
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### Features for audio levels imbalance in films between speeh/music/effects

What would be the key features of an audio track or set of tracks (like 5.1) for identifying film audio tracks that have a clear unbalance between speech levels and sound effects levels (apart from ...
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### perform linear regression by taking a batch of sample from an acoustic signal

I have an acoustic signal of a machining operation sampled at .1Mhz. I need to continously acquire a batch of n samples from this acoustic data and make a linear fit for the sample. Can anyone help me ...
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### Signal onset difference between 2 audio signals

I have 2 signals recorded in the same conditions although one was further away from the microphone than the other. I am attempted to find the difference between the time of the signals hitting the ...
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To obtain the gradient from an image, one can use a linear filter that for example is derrived from the derrivative of a gaussian. Then convolving the image with this linear filter gives you the ...
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### Given an image how should I detect this is a day picture or night picture?

I have a 2D image which contains R G and B values. I think this should be purely based on averaging of pixels and selecting the threshold to decided whether this is day picture or night one. Can you ...
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### Histogram equalization - to increase “punch” and to limit local gain?

The exercise 3.6 (Histogram Equalization) in Szeliski's Computer Vision - Algorithms and Applications asks: Convert the color image to luminance (Section 3.1.2). Compute the histogram, the ...
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### Good way to detect pulse with known width with background noise?

I'm dealing with a light sensor tracking a bursting LED. Unfortunately signal is weak and there are other light sources in environment. I've used optical filters on sensor but there is still some ...
23 views

### what are moments?

Hello all I'm using opencv after using findcontours I apply moments here is the vague wiki definition - http://en.wikipedia.org/wiki/Image_moment Can someone please explain in simpler words - ...
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### When sampling theory condition fails, what should I do?

I met with a problem: if I sample audio data at 11kHz (yes, that is slow!) for 10 seconds and apply a Fourier Transform to the data, at what frequency will a 15 kHz tone appear? So the original ...
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### How do we find the SNRseg if I have a block with 2D in time domain

I always get the answer -.0017 and it suppose to have some negative number around 30. I get the average for the plane voice then the average for the difference between plain and the encrypted voice ...
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### Equalizing 1/f noise

I am recently acquiring data through ADC on signals ranging from 0.1 Hz to 50 KHz (Fs = 128 KHz). I noticed that apart from the white noise, I have something similar 1/f noise with a cutoff near 1 Hz. ...
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### What does it mean for an image to be “Markovian”?

I've been following the recent lectures on Coursera for image processing. In the lecture on the use of the discrete cosine transform (DCT) for image compression, he says that for images that are ...
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### Question regarding filter implementation - Audio EQ Cookbook

Some of you may know the infamous Audio EQ Cookbook. You can take a look here. We tried to implement the functions there to achieve a implementation for a Lowpassfilter. However, when we try to ...
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### making video of wheel after sampling in MATLAB

Write a Matlab function named wheel.m to create a movie showing the spokes image rotate clockwise at a constant speed. The function should take parameters to change the frame rate and the speed of the ...
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### How I repeat single camshift to tracking multiple targets automatically?

I understand how the camshift for single object works.. In the paper I read for multiple targets, they do camshift tracker (single tracker) for each object, but I don't understand how they repeat the ...
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### time domain data into FFT using Matlab

I do like to generate the FFT from time domain history data (experimental lab) using MATLAB. I am not so sure if my coding is right? Can someone verify the coding. My code is as follow: ...
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### Unable to calculate the CRLB for Gaussian mixture model

I am unable to follow the steps needed to derive the Fisher Information matrix and the CRLB of an autoregressive model from the observations $x$. The AR process is excited by non-Gaussain sequence, ...
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### What are the works done till now in Video Event Detection?

I am doing a final year project on Video Event Detection. I know that there is a lot of work already done in Human Action Recognition. But instead of only human action, I want to work on event,scene ...
33 views

### System Properties; Linear, Causal, Time-Invariant, Stable?

I know the answers of the below question but I dont know why, except linear, could you explain the rest? Small tick: correct, small tick with dash incorrect answer.
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### Is DCT basicly a filter?

I am reading about audio processing for my university project and I found out that DCT basicly filters out some frequencies. I wanted to use for example high-pass filter and then DCT for compression, ...
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### Discrete Time Fourier Transform to Frequency Domain

I failed to do this question on the exam and finding it very difficult, I would be glad if you can help me solve it. How shall I start?
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### LTI system output

I compute the output of a LTI system, can someone tell me if my answer is right..? and help me with my others questions? The impulse response is: $h(n) = \left(\frac{1}{2}\right)^nu(n)$ , entry is ...
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### How to properly save an image as an eps file in GNU Octave? [on hold]

I'm trying to save an image with the eps format on GNU/Octave, but something is wrong. Here's a screenshot of what it should look like: and here is what i get: i have no idea what is happening ...
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### Least squares and auto and cross correlation

I am trying to understand why auto and cross correlation helps find the best fit line in least squares. I have an equation as stated here: $Ax=b$ -- I have not exact solution, so I use the least ...
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### Concept of combining multiple FIR Filters into 1 FIR filter

I try to combine my 7 band FIR filters into 1 FIR in order to process an audio signal. I use convolution to combine their coefficients but the effective is not the same as I apply 7 different FIR ...
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### How to plot magnitude response on MATLAB Gui [on hold]

I have a FIR digital filter with some impulse response, I would like to graph the magnitude response on Fs = 44.1kHz on MATLAB Gui - axes I tried to use fft but it has two-sided look, linear scale, ...
236 views

### Difference between Digital signal and Discrete signal

I have just started studying Digital Signal Processing. Can someone explain what is the difference between a Discrete Signal and a Digital Signal in simple words? Thanks in advance !
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### removing vocal from audio file

I want to create a program in matlab that could act like karaoke software. At this moment i have following lines of code: ...
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### Splitting of signal into different components for calculation of PSD

In BCI competition 3 dataset 5, It has been stated that we have to take 8-30 Hz frequency and break it with resolution of 2 Hz then it will result in 12 components but I am finding out only 11 ...
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### (python+opencv) haar cascade training using cloud computing

I will train my own cascade, using python and opencv. I want it to be as precise as possible, so as I read it is common that training takes one or two weeks to compile. I want to use cloud computing ...

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