# All Questions

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### How we decide sample rate and number of samples while doing dsicrete Fourier transform

I solved a differential equation numerically and I want to find the frequencies present in the solution but I am not able to figure out sample rate/frequency and no. of samples that I should take.can ...
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### 20 dB bandwidth in matlab

I have IQ values of a 8 MHz signal stored in a vector in matlab. Can someone please explain how to find the 20 dB bandwidth of this signal in matlab?
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### What is a good way to process image of our skin? [on hold]

Supposing a picture of the skin of my hand taken with a smartphone. What would be a good technology (framework/language) to process/manipulate it with a high degree of precision?
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### Computer vision, Coupon code detection, sugested algorithms

The telecommunication operator in my country has coupons that used to recharge the balance I want to develop an Android application, that with the camera can take the scratched number and recognize ...
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### Can somebody help me with some very basic questions about the fundamentals of information theory?

I just started to study information content of the source and there are some very fundamental topics I am not really clear on. These might be a long question or a series of questions. Please help me. ...
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### Mathematical model of a signal

Currently I am reading a paper on Compressive Sampling, and trying to understand each and every parts of it. When I came across the mathematical model of the signal in paper, I got confused. I have ...
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### depth values at shadow regions in images

When we take photos using flash, shadows appear at silhouettes. I was wondering if I have a Kinect like camera which can also capture a depth image along with flash image, what will be the depth value ...
16 views

### How to measure the time dependent correlation of two signals

I have two signals (time series) shown in the plot below. Just by looking at the figure, we can see that the two main peaks of both signals are very closely aligned (correlated), however the red ...
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### How to handle multiple instances of events to get trained HMM

I am trying to create algorithm that would detect some sounds like coughs, sneezes, barking. I chose MFCCs for acoustic features. Some of them could be noisy so I am thinking if MFCC is correct for ...
24 views

### Converting blobs to circles

I have this binary image with some blobs of random sizes. I would like to convert the blobs into circles of uniform diameter. it doesn't really matter what diameter but they need to be circles and ...
21 views

### How to reduce / filter out the overshot of the signal

I am very New to DSP. I would like to damp the overshoot part of the signal which is shown below. With my limited knowledge I tried to use a LPF to filter the noise. But I am getting a envelop of the ...
51 views

### Proof for determining Fourier coefficients

While determining Fourier coefficients we have this equation $$\int^{T}_{0} x(t) e^{-jn\omega_0t} dt = \sum^{+\infty}_{k\ =\ -\infty} a_k [\int^{T}_{0} e^{j(k-n)\omega_0t}dt]$$ I want to ask that how ...
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### BER Analysis of Dual hop Decode and Forward Relay

I want to perform fair BER analysis between Two-hop Decode and Forward relay communication (S-->R-->D) and Direct Transmission from S-->D. The links have Rayleigh fading. Now for fair analysis 1) ...
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### Reference : Blind equalizers for CDMA communication

I would like to know which equalizers are commonly used in practice for Direct sequence CDMA communication. For a project, I need to simulate CDMA communication with a blind equalizer and was ...
34 views

### Derive velocity and acceleration from position

I generate random spike data that represent the ouput from a rotary encoder. Here the output of my algorithm: The first plot is position, then velocity and then acceleration. Even though I downsample ...
30 views

### Baseband vs. Passband

I am a bit confused if the following signal is baseband or passband: $f(t) = x(t) \cos(2 \pi f_c t) - j \: y(t) \sin(2 \pi f_c t),$ where $j = \sqrt{-1}$. Since it is clearly not real, I cannot say ...
18 views

### Why is this projection wrong?

I am trying to figure out why a 3D cube doesn't project in the right place in the image. I start with the camera at origin and the cube centered at (0,0,1) world ...
27 views

### Signal to noise ratio (SNR) calculation in an OFDM system

I'm trying to simulate the bit error rate (BER) of a modified 802.11 OFDM system where only $\%80$ of the power budget is allocated for transmission and the rest is allocated for other purposes. Let ...
22 views

### Why is my filtered signal offset from 0?

I have some random noise which is recorded from an accelerometer. This particular axis has been preprocessed by decomposing the data into frames which are then detrended to ...
23 views

### MFCC coefficients

I have read this, this, this, this and this as a reference for computing the MFCC for a given wave file. Although, I am sure the values look wrong. In short I followed the procedure in link 5. ...
57 views

### At what amplitude does spectral leakage start to be noticeable in the phase spectrum?

I understand that discontinuities at the boundaries of a finite signal may introduce spectral leakage, that alter both the amplitude and phase spectra of the FFT, specially at low amplitudes. That is ...
23 views

### Sketching a tri signal with horizontal shift

I'm unsure how to sketch a tri signal with horizontal shift. Eg , let's say we want to sketch tri((t-4)/4). Can I reduce it to tri( (t/4) - 1 )? This would mean sketching a tri(t/4) signal and ...
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### Filling hatched areas in image

I'm trying to extract / fill the walls in a floor plan, the walls are filled with a (cross-)hatch pattern at a more or less fixed angle. I've managed to remove most of the "noise" by masking the DFT ...
17 views

### Comparison of Shapes in Plots

Recently, I asked a question: Comparison/Difference between two distinct plots (DSP StackExchange), where I wanted to find a good metric to compare two plots. Then, from the answers, I would try to ...
16 views

### Artificial Neural Network Example Problem

I was looking at an example of a NN but I dont understand in the Answer i where the .68 come from or .6637 This is the link of the tutorial
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### Guard Interval Correlation for a given Impulse Response in OFDM system

I've been given a channel response of $$h(n) = \delta(n) + A \delta(n -D)$$ where A and D are arbitrary constants. What would be the output of Guard Interval Correlation (GIC) symbol ...
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### Baseband vs Passband modulation

I am taking a graduate level course in Networking theory and applications and I am still a bit shaky on the difference between baseband and pass band scheming. The book I am using is Computer Networks ...
49 views

### Signal reconstruction in compressed sensing with a simple vector signal as an example

While going through the different types of reconstruction algorithm as mentioned in lecture notes in Compressed Sensing by Richard G. Baraniuk, I came to know that minimum $l_1$ norm reconstruction is ...
28 views

### What is the Fourier tranform of $x(t) = \mathrm{sinc} ^2 (t)$ using duality properties?

Is it $\mathrm{tri}(t)$ or $\mathrm{tri}(-t)$? Duality properties states that $X(t) = x(-f)$ My answer is $\mathrm{tri}(-t)$? Is it correct?
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### Why pulse length can define axial resolution?

One book about ultrasonic imaging process says,spatial pulse length=wavelength*number of cycles in pulse.And axial resolution=1/2*SPL. Why there are several cycles in pulse? Through FFT, indeed we ...
20 views

### comparing audio file

I have a question about comparing two files there is a database of music files I want to divide a music file to some parts and then distinguish that which portion belongs to which music file. I want ...
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### How does the Magnitude of an FFT relate back to the Time Series wave it was created from?

Alright, to start out I am a mechanical engineer with very little circuits and digital signal processing background. So please excuse my ignorance as this is far out of my usual territory. When ...
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### What is a good book reference on the definition of “subharmonic frequency”?

Is there a good book reference on the definition of "subharmonic frequency" as integer fractions of the highest available frequency?
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### Wavelet decomposition

For the following code, X=[2 2 3 100 4 0 98 100 90 2 3 67 98 0 6 6 89 9 21 78] [C,L]=wavedec(X,N,'db1'); where N is the ...
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### Modification of Accelerometer Data for Feature Extraction

I have accelerometer [x,y,z] data recorded from various activities. I am not looking at any filtering techniques (which I have seen within this forum) because I ...
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### hdr compression using adaptive-learning codebook

I've implemented the following adaptive-learning algorithm for hdr image compression. paper can be found here I intend to work with grayscale images only. I get bad results, so I'm trying to find ...
13 views

### System Identification with periodic signal confusion

I want to find the ETFE (Empirical Transfer Function Estimate) of the system $G(e^{j\omega})$: Where $H(e^{j\omega})$ is some filter that zero-mean white Gaussian noise $e(k)$ passes through. Let's ...
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### Could anyone help me write a code for compressed sensing of an audio signal? [on hold]

Initially the audios signal is divided into frames and compressed sensing is used and after that it is reconstructed using the Basis Pursuit and Orthogonal Matching pursuit reconstruction algorithm.I ...
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### Fourier transforms of random processes

In the Wikipedia article on Brownian noise, the Fourier transform of Brownian noise is determined. How is that Fourier transform defined? It seems it is a non-random quantity there, so it is not ...
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### Question on sketching the amplitude spectrum of signals

I can't seem to understand the sketches of the amplitude spectrums provided in my tutorial solutions. For this part , I understand that X(f) is basically sampling (T/Tp)sinc(Tf). But from what I ...
34 views

### Working out integration of basic signal functions

As the title suggests , I'm having problems working out the integration of some basic signal functions. Shown below are the questions and my workings. For some reason I'm just unable to get the ...
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### Finding Distance between Cameras in Stereo Vision

We know how to create disparity map from stereo vision with OpenCV. My question is How can we find/estimate distance between cameras from two image taken from these cameras in OpenCV?