# Questions tagged [reconstruction]

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166 views

### 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 ...
128 views

### Calculate the intersample peak of a periodic sequence?

Similar to Calculating the PDF of a waveform from its samples, but for periodic sampled signals, and I just want the peak. Is there a way to calculate the highest inter-sample peak of the ...
101 views

### What algorithms can automatically determine a 3D scene from one or a few 2D images?

For a project I'm doing, I'm trying to model a scene based on a phone camera's video input, and then insert arrows into it that indicate direction in three dimensions. I've looked around, and this ...
188 views

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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 ...
444 views

### 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 ...
647 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 ...
589 views

### 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 ...
199 views

### 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 ...
215 views

### 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 ...
87 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 ...
61 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 ...
53 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 ...
176 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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### 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: ...
105 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 ...
613 views

### 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 ...
2k views

### 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 ...
7k views

### 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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### 2D IFFT implementation

I have a problem where I need to obtain 2D IFFT of a $81\times64$ signal. However, if we denote the reconstructed image $I_{m,n}$, its coordinates will be $M\times N$ but the k-space signal is sampled ...
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: ...
57 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 ...
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 ...
14 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 ...
12 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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### 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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### 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 ...
375 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 ...
280 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 ...
55 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 ...
429 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 ...
782 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 ...
108 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 ...
715 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 ...
403 views

### 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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### 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 ...
847 views

### 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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### 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 ...
68 views

### 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 ...