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Questions tagged [reconstruction]

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Image reconstruction from k-space data

I have k-space data related to an image. k-space data is made of Kx, Ky, signal arrays of 4100x1. What I have done for image reconstruction is: $$I_{m,n}=\sum_i Signal_i \space e^{2\pi j(\frac{K_{x}^...
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2answers
38 views

Complex signal sine reconstruction

Noob here, I read that any signal can be made by putting together sines and cosines, it always shows some kind of basic harmonic wave with constant amplitude such as square wave. I understand that ...
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1answer
56 views

Reconstruction of sampled band-pass signal

I am pretty new to signal processing. I am currently trying to reconstruct a sampled band-pass signal created with the filtfilt and ...
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0answers
8 views

Visual Slam, relative magnitude of translations from 3 images?

given a image sequence with 3 RGB images img1,img2,img3 , each shot the same scene with slightly different pose. I can compute two essential matrices E1 and E2 using openCV, where: ...
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2answers
884 views

What Is the MATLAB `imreconstruct()` Useful For?

Could some one tell reasons to use the MATLAB imreconstruct function when processing images? I already have studied the topic and what the function actually does to ...
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0answers
47 views

A Different Reconstruction Operation

I want to understand what is happening in below operation: Here, x(nT) is sampled signal (say oversampled) and h(t) is its ideal reconstruction filter. As highlighted in the expression, amount of ...
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1answer
412 views

Signal Resampling by a non integer factor with convolution

to start I am a newbie in signal processing, I just started a month ago so please be as detailed as possible. From what I understood to resample a signal by a non integer factor you can do an ...
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1answer
11k views

Discrete Wavelet Transform - Visualizing Relation between Decomposed Detail Coefficients and Signal

I'm trying to directly visualize the relation between discrete wavelet transform (DWT) detail coefficients and the original signal/its reconstruction. The goal is to show their relation in an ...
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0answers
28 views

What is the best way to separate data using compressive sensing?

In the book Compressed Sensing by Kutyniok et al, the author talks about data separation using sparse representation. In summary, if we have a signal vector $x = x_1 + x_2$ Then, it would be ...
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1answer
125 views

How can you 'perfectly' reconstruct phase for transients in a modified audio absolute spectrogram?

I am currently working on the absolute spectrogram of an input audio signal. I am using non-negative matrix factorization to separate out the rhythmic components (bass drum, snare drum and hi-hat) of ...
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0answers
13 views

How to get NMF sparse component factors

In the NMF framework, whenever I want to get a sparse component, I set the rank to 1 (lowest possible) and get the W and H matrices of the low-rank component by doing a multiplication of the resulting ...
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4answers
903 views

reconstruction filter - How does it actually work?

I'm trying to form my own understanding on the religious war around using 192kHz as a sampling rate for playback (the Internet seems to have a wealth of material on both sides). I'm struggling to ...
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0answers
29 views

Recreating an image from random samples?

Assume that I have samples from an image, but the samples aren't on a grid, but instead there are multiple lowres versions of the original where the sampling locations are slightly jittered, so the ...
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1answer
27 views

MRI image reconstruction - reduced scan pecentage

I have an MRI kspace from a siemens 1.5 T scanner with reduced scan percentage ( sampled truncation by not acquiring the most peripheral lines in kspace). The kspace plot in matlab look like below. I ...
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0answers
10 views

Pascal Voc 2012 Annotaions for 6D viewpoint(pose) estimation

Everyone, I am working on 6D pose estimation and I have to predict a rotation matrix (Euler angle) and translation. Now In Pascal Voc annotations are in the form of azimuth, elevation and distance ...
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0answers
18 views

How to choose $\lambda$ is compressed sensing

I am trying to reconstruct a signal using basis pursuit denoising of the compressed sensing framework (which is basically lasso), $\min\limits_{x} \frac{1}{2} || y − Ax||_2^2 + \lambda ||x||_1$. Here, ...
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1answer
84 views

How to extract a smooth contour from a set of points in 3D?

I am trying to segment a 3D volume. The outcome of all my volume segmentation algorithms is a set of candidate points in 3D space. Now I need to smooth this point cloud and fit a closed surface it. My ...
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0answers
36 views

What are the constraints in design of discrete orthogonal wavelets?

Can anyone point me to literature that explains a quote from here : Why is a wavelet transform implemented as a filter bank? So not all wavelets can be implemeted perfectly (invertible) with ...
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0answers
354 views

Recover Audio from Spectrogram Image

I have applied transformation(Constant Q Transformation) to my audio time domain signal, this gives me Frequency vs Time representation. Now, the CQT values consists of complex values(84*260), but ...
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1answer
60 views

What's wrong with this Whittaker-Shannon-Kotel’nikov interpolation implementation?

I tried to implement Whittaker-Shannon-Kotel’nikov interpolation formula but I get unexpected results: the reconstructed signal lags with respect to the original. I know that I can not expect a ...
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0answers
65 views

Proving Nyquist Sampling theorem for strictly bandlimited signals

I understand that the Nyquist sampling theorem dictates that the minimum sampling frequency, $f_s$, be s.t. $f_s > 2B$, where $ B $, is the bandwidth of the signal. I have read the explanation for ...
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1answer
48 views

Very basic question about filters in signal reconstruction

I am studying digital signal processing and I would like to ask a question about sampled signal -> original signal reconstruction filters. Most textbooks use a box filter or a tent filter to show how ...
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1answer
254 views

What is Finite Rate of Innovation Signal?

I have read about Finite Rate of Innovation signal by Martin Vetterli in here. But i do not understand several basic things The paper said that finite rate of innovation is the number of degree of ...
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1answer
204 views

Multiple-image dense point cloud reconstruction with camera extrinsics/intrinsics

I have the following data available: Images from different angles X, Y, Z, pitch, yaw, and roll for each camera/image, together with the timestamp Lens distortion parameters and intrinsic camera ...
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1answer
171 views

Is it possible to generate depth map from graycode sequence without using printed calibration patterns?

In a camera-projector system, if only the camera's intrinsics are known, is it possible to generate the depthmap fully automatically through a graycode sequence without any manual calibration process (...
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1answer
267 views

signal reconstruction [closed]

I'm new to DSP so the question might seem a little bit stupid: When using a low pass filter (say Butterworth filter) with Python, I came across an algorithm with which I can reconstruct my signal ...
1
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1answer
268 views

What Are the Types of Deconvolution?

I am totally new to image processing and wanted to ask you if you could confirm what I understood. It is about deconvolution: From what I read we find 2 main types of deconvolution: 1. Analytical <...
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1answer
134 views

image reconstruction using a set of kernels

I try to be brief. For what I understood Convolutional Neural Network CNN for style-transfer extract/learn the main features of source Image. I think these features basically are Kernels (of different ...
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0answers
54 views

Construct a signal that is multiplied by a white noise?

Can we reconstructs a signal after it is being multiplied (not added) by a random noise (not with the normal distribution)? Lets say I have S=10*sin(2*pi*5*t) for t=[0:.001:1] and I have a random ...
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2answers
258 views

Confused on application of Anti-Aliasing Filter

I have a question about the use of anti-aliasing filters prior to sampling a finite time signal and if they actually help anything. The point of the anti-aliasing filter is to remove high-frequency ...
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0answers
175 views

Reconstruct signal from its Spectrogram only

The spectrogram of a signal throws away the phase information, but it is said to be possible to reconstruct the signal only from the spectrogram [1] via $$s(t) = \frac{1}{2\pi s^*(0)}\int_{-\infty}^{\...
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1answer
246 views

Interpolation formula for two dimensional signal reconstruction in the frequency domain from polar samples

In the book, Advanced Topics in Shannon Sampling and Interpolation Theory by Robert J. Marks II, one may find an interpolation formula for reconstructing a two dimensional signal from regular polar ...
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0answers
128 views

Perfect reconstruction of 2 channel filter bank

I am studying Perfect reconstruction of 2 channel filter bank for using Biorthogonal Spline wavelet for decomposing ECG signal. I am using Wavelets and Filter Banks By Gilbert Strang, Truong Nguyen to ...
1
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1answer
224 views

Reconstruction of a signal using an ideal DAC

I think I was able to do part (a) correctly, but now am stuck on part (b). I don't know how to approach this part or what is the theory behind it. My MATLAB code is shown below. Please let me know if ...
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2answers
893 views

Is magnitude information enough to reconstruct an audio signal

I have used an MMSE STSA estimator to obtain the magnitude of an audio signal. The original signal is combined with white noise and I used an algorithm given in an old research paper by Ephraim and ...
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2answers
753 views

Signal reconstructed using IFFT: amplitude scale larger than input

I am trying to test reconstruction of signal from IFFT. Below is the python program. I break the signal into overlapping windows and do FFT after multiplication with window function. Then I apply IFFT ...
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2answers
636 views

Reconstruction of bandpass filtered signal from decimated version of itself

I know how to up-sample a discrete, real signal (by an integer factor n) that is band-limited to frequencies between $f_1 = 0 \mathrm{Hz}$ and and $f_2$: Just insert $n-1$ zeros between every original ...
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1answer
249 views

Inverse wavelet transform on wavelet coefficients

I have a data set which consists of Morlet coefficients for 7 channels in 18 bands. When I try to use inverse DWT in Matlab to get the raw data in time, using this code: ...
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2answers
104 views

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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1answer
91 views

What is the general formula for radon back projection for a javascript implementation?

I'm aiming to implement a simulation of computed tomography back projection in javascript/HTML5 canvas. Trying to figure the correct approach for doing a back projections and I have been studying the ...
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2answers
280 views

Random (Over) Sampling signal and perfect Reconstruction in Nyquist form?

Imagine we have band limited signal with bandwidth of $B$, so the required Nyquist rate would be $f_{nyq}>2B$ that is oversampled with rates $f_s$ where $f_s = M*f_{nyq}$ and $M$ is random and $M&...
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1answer
193 views

Minimization of Essential matrix

A problem in computer vision and 3d reconstruction is getting the camera's intrinsics parameters. A common solution is to use an object in which one knows the measurements of the shape before hand, ...
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2answers
1k views

What is the difference between image restoration and image reconstruction?

I am new to image processing. I don't know whether this is the right place to ask, but what is the difference between image restoration and image reconstruction?
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1answer
65 views

Hybrid Sampling Scheme Idea?

I am facing a problem which I could not find any robust solution for . Assume we have a signal, $x$, composed of sum of a few sinusoidal. e.g. $$x=A_1\sin(\omega_1t+\phi_1)+A_2\sin(\omega_2t+\phi_2)+...
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1answer
334 views

Reconstructing Signal From Its Cyclic Autocorrelation

Can a signal be reconstructed from its cyclic autocorrelation? Specifically, if we know $$ R^{\alpha}(\tau) = \int{x(t)x^{\ast}(t-\tau)e^{-j2\pi\alpha t}\mathrm{d}t}, $$ can we reconstruct $x(t)\in\...
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1answer
473 views

Shannon interpolation formula for downsampled data with an “almost ideal” low pass filter

Let $x[n]$ be a discrete time signal with DFT given by $X(f)=\sum_n x[n]e^{-2\pi inf}$ supported on $[-1/2M,1/2M]$ with $f\in[-1/2,1/2]$. I can then down-sample to get $y[n]:=x[nM]$. Then, let $$\...
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0answers
804 views

Sinc interpolation formula for signal reconstruction in frequency domain from bipolar samples

As per the title, I was wondering if there was a $\operatorname{sinc}$ based interoplation formula for reconstructing a signal in the frequency domain which has been sampled with respect the bipolar ...
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1answer
107 views

How to choose an interpolation method for seismic ground motion signals

I am working with seismic ground motion records from the PEER database. They are acceleration measurements that are band limited to 50 Hz and sampled at 200 Hz. I use these records to drive an ...
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1answer
708 views

Two-View 3D reconstruction using the sparse Levenberg–Marquardt algorithm

I have trouble implementing the Levenberg-Marguardt algorithm as described in the book Multi View Geometry in Computer Vision. To be more specific I have trouble calculating the partial derivatives ...
1
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1answer
31 views

How to sample $f:=f_{1}\cdot f_{2}\cdot…\cdot f_{K}$?

Let $f_{k}$ be $\sigma_{k}$-bandlimited, $k=1,2,...,K$ and define $f:=f_{1}\cdot f_{2}\cdot...\cdot f_{K}$; then how should I choose $T>0$ such that we can recover $f$ from samples $f(nT)$? ...