Questions tagged [reconstruction]
The reconstruction tag has no usage guidance.
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Computing sine phase and amplitude
I need to compute the DC offset, amplitude, and phase of a sine wave and I would like some help validating that my current technique is correct and get some tips to improve my technique. I am a DSP ...
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Does Zero Padding Work as Advertised?
I have trouble accepting the merits of zero padding in the frequency domain to give more points in FFT. Wonder if anyone else has similar thoughts.
The mathematical 'proof'for the validity of zero ...
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Simulating noise in computed tomography reconstruction
In the research of the computed tomography (CT) reconstruction, one needs to simulate the noise during CT projection and capturing. Then, my questions are:
How about the proper noise type?
How to ...
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Signal values we will 'miss' between sampling instances during sampling of band limited signals
According to the Nyquist–Shannon sampling theorem, any continuous time signal with a bandwidth $B$ smaller than Nyquist frequency $f_N=f_s/2$ (with $f_s$ the sampling frequency), which is sampled at ...
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Question about MRI signal construction
As I understand it, in MRI, a line in k-space is usually acquired while the readout gradient is applied. So during the application of this gradient the protons spin at different frequencies along the ...
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MRI reconstruction using windowing based apodization
I am trying to apply windowing to do MRI reconstruction. I have a 256 point one dimensional k-space samples which look as follows:
Here, the real part(green) is flat around 0 and the blue curve is ...
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Random sampling vs uniform sampling
In this paper of Lustig, he speaks about a something which appears unintuitive: sampling at random may exhibit better performance than sampling uniformly. I tried to understand this starting from page ...
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Complex numbers in $\tt ifft$ of an MMSE amplitude estimator
I am trying to reconstruct a signal from a noisy speech using an MMSE algorithm proposed long time ago by Ephraim and Malah (1984). After going through the algorithm, I got a matrix A which represents ...
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Method of reconstructing a band-limited signal from discrete samples
I understand current cell phones use digital communications. Given that this industry brings in billions of dollars each year, there is much incentive to get the best performance possible. So what ...
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Reconstruction of voice from distorted recordings
I would like to know how much of the sound of my voice getting through various types of walls can be reconstructed with easily obtainable software and algorithms.
My plan is to place a microphone on ...
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Upsampling and zero order hold
Maybe to someone this question may seem quite easy but I have a problem grasping it. Namely, assume that we have two systems A and B with sampling rates $f_A$ and $f_B$ where $f_A>f_B$ and $R=\frac{...
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How can a signal have two maximum frequency components?
$x(t)$ can be exactly reconstructed from its samples at $\omega_s = 10 \textrm{ rad/sec}$. My conclusion is that the maximum frequency component in $x(t)$ is $5\textrm{ rad/sec}$. But I'm being told ...
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image type after an ifft reconstruction
I reconstruct images from MRI k-space using ifft and root-sum-of-squares method.
...
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How to reconstruct 2D flat image from a series of pictures of a tube
I have pictures of an oesophagus (ie a tube) taken under standard white light looking down the tube. I have about 10 images taken over 20cm in series. The image looks forward down into the tube and ...
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How to reduce reconstruction noise from a filtered back-projection reconstruction of a circularly symmetric image?
I need to perform tomographic reconstruction of an axially symmetric object. Because of the axial symmetry only one projection of the object (one angle) was taken. I implemented the filtered back-...
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Sample and reconstruct a real exponential (just one period)
I have a function with an equation:
$$C = 1.6925\left( e^{-0.136t}-e^{-1.192t}\right) $$
Where $C$ is real and $t$ represents time in hours. Beneath is the representation of my function.
I am ...
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Ideal reconstruction after down sampling
The signal $x_a(t) = \cos(2\pi450t)$ is sampled.
F = 450
Fs = 1000 Hz
f = F/Fs = 450/1000 // Sampling theorem is fulfilled
x(n) = cos(2*pi*(450/1000))
The ...
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linear interpolator replacement for the sinc function
How to find an optimum linear interpolator replacement for the ideal sinc function? The reason is for the hardware implementation ease.
For example when I use sinc interpolation:
...
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optimization of Image Reconstruction Algorithm using Genetic Algorithm in Matlab
I'm trying to optimize an image reconstruction algorithm using genetic algorithm.I took initial population size as 10.I have an input image an 10 reconstructed image.fitness function is the difference ...
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What is done to minimize distortion due to the hold operation?
A hold operation can be modeled using a step function over one sampling period i.e.
$R(t) = 1/T * (h(t) - h(t-T))$, $h(t)$ the step function
In frequency domain this is equivalent to
$R(jw) = e^{-...
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Reconstructing time domain signal with Hanning window
I am currently working on a frequency domain real-time application on a digital signal processor. Currently for one time frame of my algorithm I read in time domain data into a buffer, perform a ...
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What are the frequency components of a sampled signal after low-pass filtering?
A continuous signal $x_a(t)$ is a linear combination of sinusoids of frequency 250 Hz, 450 Hz, 1 kHz, 2.75 kHz and 4.05 kHz. The signal $x_a(t)$ is sampled at $f_s=$1.5 kHz, and the resulting digital ...
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Ideal Reconstruction of Upsampled Signal
Problem: The signal $cos(2\pi14100t)$ is sampled at $F_s = 400 Hz$. It is then upsampled with a factor 3 and then reconstructed ideally with a new frequency $F = 500 Hz$.
I now want to find the new ...
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Are reconstruction filter always needed?
in mixed (digital and analogue application) where you have to convert a signal from continuous to digital time domain and then back again to continuous time an anti-aliasing LPF is needed and in ...
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Beyond cross-eyed 3D (VR application)
Making static 3D image is very simple - we just take image pair with something like this:
then we can see 3D image by putting the left and right eye image side by side and crossing eyes or ...
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Incoherence: Compressed Sensing (CS) vs Matrix Completion (MC)
I am seeking a clarification of the concept of Incoherence within the MC framework.
Specifically,
1) the literature mentions the application of a "strong incoherence" given a set of assumptions. ...
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Computing shifted signal without first reconstructing
Looking for a solution to the following problem:
A signal $x(t)$ is band limited to $B$ Hz, and sampled above the
Nyquist rate, with corresponding $f_s = 1/T$. If the sampled signal is
given by
...
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reconstruction of time series in SSA
i am trying to reconstruct time series from SSA ,because according to this link
http://en.wikipedia.org/wiki/Singular_spectrum_analysis
there is procedure
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Stochastic process inference from partial observations
Consider a set $U$. My signal is a piece-wise constant "function"
$Sig: t \mapsto s$, i.e. the signal at time $t$ equals to some subset
$s \subset U$. One can see $Sig(t)$ as a stochastic process.
...
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Gradient Domain Reconstruction - Scaling Problem
I am implementing reconstruction of image from gradient domain. This requires solving the following partial differential equation (a Poisson equation) on a 2D grid:
$$\nabla^{2}I=\mathbb{div} G$$
$\...
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Sampled signal reconstruction using matlab
I have a wav file recorded from my smartphone's mic, and I want to reconstruct the sampled signal and plot the reconstructed signal. After some research and search, I was able to get the following ...
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Reconstruct DWT for each cD1,cD2,cD3 and cA3 signals
This question must be basic for this forum, but I'm only start working with DWT recently, and I was working with CWT before.
I ...
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Upsampling Methods for Computed-Tomography
I have two sets of data of given Field of view, one of them only covers a subset of the FOV of the other. I therefore want to upsample the one with the larger FOV to combine it with the other one.
So ...
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Reconstructing a partially deleted image through wavelets
I am trying to form an approximation of the wavelet transform from a partially sampled image.
Reconstruction in the 1D case is easy. We have $w = h x$, with $w$ as the wavelet coefficients, $h$ as ...
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Explanation of LidarBoost Algorithm?
I am trying to understand the LidarBoost algorithm as explained in this paper (PDF warning).
I don't understand how they take the original depth-images $Y_k$ and transform them into the up-sampled ...
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Texture mapping on a 3D face from 2D face image
I have 3D points (xyz) of a face image and I have 2D face image of the same person.
The 3D points of the face are such that If I project the points to 2D plane, it matches with the 2D face image.
I ...
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Radon Transform reducing the number of parallel beams (MATLAB)
I am trying to understand different filters' and other things' effects on Radon Transform by using MATLAB. First I upload an image, then take its Radon transform with radon function and then ...
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Remove noise on edge (compression deffects)
I have the images of cartoons, that were compressed. The example:
They have such noise, that is not easy to delete.
Even though the pixels are on the gray background, the noise pixels can be of ...
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what is the effect of variation of duty cycle of sampling frequency on a reconstructed signal
I have been asked to study an experiment which says "what is the effect of variation of duty cycle of sampling frequency on a reconstructed signal"
I am not an electronics/electrical engineer I am ...
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What is the procedure to obtain a 3D face dataset? Can anyone suggest a good 3D face dataset?
Project Description:
Input:
Frontal Face Image
Expression
Angle
Size
Details:
I have to convert the input frontal face image into 3D face and simulate the ...
