Questions tagged [interpolation]

Interpolation is a method of constructing new data points within the range of a discrete set of known data points.

Filter by
Sorted by
Tagged with
1
vote
0answers
129 views

How to shift with spline interpolation?

I have a sampled pulse shape: $ h = [1, 0.5]$ and I do not know what is its real underlying continuous-time pulse. I want to compute the samples of $h(t-\Delta t)$. If I write the continuous pulse ...
0
votes
0answers
520 views

Optimal signal sampling reduction method : Decimation, interpolation or both?

I have a function with an equation: \begin{equation} C(t)=1.6925\left(\exp^{-0.136t}- \exp^{-1.192t} \right) u(t) \end{equation} where u(t) is a unit-step function. Then, denoting the Fourier ...
1
vote
0answers
42 views

How to proceed with this convolution problem?

If $$\alpha_k = \sum_l a_l \ \ g((k-l)T-l\Delta T)$$ $$s_k = \sum_l \alpha_l \ \ q((k-l)T+k\Delta T)$$ where $a_l \in \pm1$ and $g(t) = \frac {\sin(\pi t/T)}{\pi t/T}$ and $q(t) = \frac {\sin(\pi t/(...
4
votes
1answer
1k views

How to apply a Butterworth filter to data of varying sample rate?

I am trying to apply a Butterworth bandpass filter to accelerometer data of my smartphone. However, the accelerometer samples I receive do not come at regular intervals. Sample frequency varies ...
2
votes
0answers
661 views

How do I interpolate between bins on an FFT in python?

I have four frequency peaks, which I have after applying FFT. Now I want to know precise values of these frequency peaks. there are different interpolation methods. How can I use this method of ...
-1
votes
1answer
237 views

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: ...
2
votes
4answers
756 views

How to compare the qualities of two interpolation (image resizing) algorithms?

I am implementing image resizing algorithms (Bilinear, Bicubic, Lanczos and a few others). How do I quantitatively compare them? I am thinking of considering a large sample of images and running ...
1
vote
2answers
1k views

Sinogram Fourier Analysis Doesn't Show Clear Bow Tie Shape

I'm working on finding the center of rotation of a set of test tomographic projections in order to perform 2D reconstruction. I'm trying to implement the algorithm to find center of rotation as ...
3
votes
0answers
443 views

How to subsample shift with sinc interpolation?

Does anybody know of a way to shift data by a fraction of a sample by using sinc interpolation? For example, shift an image to the right by 0.1 pixels. I'm struggling to find a formula or reference ...
4
votes
2answers
3k views

Difference between Sub Sampling and Down Scaling of Images

I know that there are many ways to upscale (interpolate) an image using bilinear, bicubic, sinc... Somehow, these same algorithms can also be used to downscale an image. But when it comes to ...
0
votes
1answer
1k views

What is the difference between Linear Interpolation factor and Sampling rate conversion factor?

I have come across sampling rate conversion factor, which is given by: S_factor = F_new/F_old If F_new > F_old, then s_factor > 1 ...
1
vote
2answers
141 views

Explanation relevant to the filter response ($\mathrm{sinc}$ interpolation) - Equation $(2)$ in my question

At present, I am learning the theory of operation of resampling for bandlimited periodic discrete signals using $\mathrm{sinc}$ interpolation. I am developing a design flow and having difficulty in ...
0
votes
1answer
80 views

How to determine best fit from two?

I'm studying some variances ($\sigma^2$), that in my case, they must depend by velocity squared $v^2$. So, in my experimental proofs, I have plotted a graph of $\sigma^2/v^2$, and I was hoping to ...
3
votes
1answer
586 views

Low order sinc interpolation vs. polynomial interpolation for variable fractional delay

I'm implementing a variable fractional delay element for use in online audio processing. Applications include ie. Karplus-Strong synthesis, flanger, chorus, echo, vibrato. I'm not oversampling, so ...
3
votes
2answers
16k views

What is the difference between cubic interpolation and cubic “Spline” interpolation?. How to use it for upsampling purpose?

After considering a couple of advices and suggestions for upsampling techniques here, I finally converged to use the cubic interpolation technique to estimate the voltage values corresponding to ...
1
vote
1answer
97 views

Derivative of signal with missing samples

I have software that tracks an object moving (in the x-dimension only) across a video shot from a stationary camera. I need to find the velocity and acceleration of the object as functions of time. ...
1
vote
0answers
3k views

Image super resolution algorithm in Matlab

I'm trying to implement a simple Image super resolution algorithm (DWT-Based Resolution Enhancement ) in the following paper http://www.ripublication.com/aeee/52_pp%20%20%20405-412.pdf I tried to ...
0
votes
1answer
67 views

Modeling multipath distortion and shifting by fractions of a sample

I am working on modelling some FM transmitted signals, and I'm trying to figure out how to model the effects of multipath channels. The most obvious method is to delay the signal by some integral ...
1
vote
0answers
203 views

MATLAB implementation Spline Fitting

Let $s(t)$ be a signal that can be approximated by a uniform spline function of order $K$ (say $K=2$): $$s(t)\approx\sum_{n\in \mathbb{Z}}c_n\beta_+^{(K)}(t-n) $$ Suppose that we know the ...
0
votes
1answer
1k views

PSNR of two images of different size in matlab

I performed bicubic interpolation on a 256*256 image(img) dest = interp2(img,'bicubic') and i got a 511 * 511 image.I want to compute PSNR of a 512 * 512 image(...
4
votes
1answer
9k views

Bicubic Interpolation

I'm trying to do bicubic interpolation on an 8*8 matrix(image) shown below. ...
3
votes
2answers
191 views

upsampling by huge factor

Assume i have a discrete signal, which i want to up-sample by factor 100. Up-sampling using poly-phase algorithm sounds like a bad idea, in terms of cache low-efficiency due to low space-locality of ...
1
vote
0answers
72 views

Interpolation methods for radar and acoustic imaging and potential pitfalls

A) What are the most common methods used to remap data for current generation imaging radars and acoustic sensors? B) What are some of the pitfalls in these methods? For example, in the past, at ...
3
votes
0answers
536 views

Phase noise estimation and compensation schemes

Brief background There is a known problem that high order modulation schemes suffers from phase noise of reference generator. It's very important issue for e.g. line-of-sight (LOS) modems exploiting ...
6
votes
2answers
1k views

Artifact in Bicubic interpolation

I wrote an algorithm to do bicubic interpolation of an image. I used the method desribed in the wikipedia page. On simple images, the result looks good, but on more complex ones, I got strange ...
1
vote
1answer
1k views

Variable sample rate interpolation

I have a set of data over which I would like to interpolate, with a sampling rate say about $f_0$ Hz with a significant uniform random sampling jitter, such that it's more or less: $$f_0 - \frac{1}{4}...
1
vote
0answers
62 views

Interpolation methods for radar and acoustic imaging [duplicate]

-----------------deleted by author to merge with valid account
1
vote
1answer
1k views

How to downscale an image with interpolation by a factor larger than interpolation kernel size?

I'm experimenting with image resizing techniques and algorithms. Specifically, I'm significantly downsizing images, e. g. from 2048x1536 to 64x48 - 32 times. Now, say I'm using a 4x4 kernel. Right now ...
5
votes
2answers
791 views

How to deal with signal not equally spaced in time when performing FFT?

I wonder to know what is the best way to handle not equally spaced in time signal when performing FFT ? I guess it depends on the signal itself. I work with signal with about 1000 - 5000 samples and ...
0
votes
1answer
266 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 ...
7
votes
2answers
13k views

Savitzky-Golay filter parameters

I am trying to smooth a series of data in order to obtain a continuous function that could represent that given data set. It came out that the Savitzky-Golay method could be a good way. Now, I don't ...
3
votes
0answers
609 views

Interpolating on the borders of differently-resolved images

I'm creating a three-dimensional model of the earth based on SRTM height data. The data set is pretty huge, so only a small fraction of the data is available at any given time. The height data is ...
2
votes
3answers
3k views

Trying to understand downsampling and then upsampling

I am trying to understand how this works, specifically, what the DTFT of each step looks like in each step of the chain (for understanding). I am not looking for an answer like because the input ...
1
vote
3answers
3k views

filter and resample or resample and smooth?

Currently doing some signal analysis in python for a major project in my physics degree which is due really soon. I need some help! Say I have two signals, f(t) and g(t) which are recorded over the ...
1
vote
1answer
731 views

Upsampling signal for cross correlation

I am recording a 17khz signal at a sample freq of 44.1khz. I want to perform cross-correlation between the received and transmitted signals for calculating TDOA. But when I do xcorr, the results are ...
3
votes
2answers
6k views

How do you interpolate between points in an image (2D), e.g. using splines?

I can understand just fine how to use 1-dimensional interpolation on data points where one coordinate is a function of the other: y = f(x). However, when we have an ...
1
vote
0answers
145 views

Extend linear spline interpolation to cubic spline interpolation - how calculate derivative

I'm trying implement in Java cubic spline interpolation based on this document: http://www.geos.ed.ac.uk/~yliu23/docs/lect_spline.pdf At first they show how to do linear spline and it's pretty easy. ...
7
votes
3answers
4k views

Why Is Bi Quadratic Interpolation for Image Resampling / Interpolation Rarely Done?

Related question: What are the practically relevant differences between various image resampling methods? Bilinear and bicubic interpolation for image resampling seem to be fairly common, but ...
8
votes
4answers
7k views

Higher order spline interpolation

I noticed that spline interpolation with a degree higher than 3 (everything beyond cubic splines) have a very high interpolation error, hence the prediction is mostly awful. I've come across various ...
1
vote
0answers
84 views

interpolation of filter coefficients

i've read that it is possible to interpolate between two sets of filter coefficients (if they are close of course), but how to interpolate between two sets of coefficients which are of different ...
2
votes
0answers
139 views

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 ...
3
votes
2answers
1k views

polyphase sample rate conversion with non-integer factor

I want to do sample rate conversion by subsequently upsampling with factor I=5, and then downsampling with factor D=9. I have designed a nyquist sample rate conversion filter h() of length M, with ...
2
votes
1answer
2k views

Convolution Based Image Interpolation

From a book, I learned that image interpolation (or upsampling) can be written as a convolution like this: $$g(i,j) = \sum_{(x,y)}f(x,y)h(i-rx,j-ry)$$ while $r$ is the upsampling rate. But I have a ...
0
votes
1answer
763 views

What are the effects on filtering upsampled data without interpolation?

I have an application that displays several signals from different sensors at various sample rates. In order to display the data, I "stretch" the signal by repeating samples to match the highest ...
3
votes
2answers
4k views

Is interpolation (interp1) better than FIR filtering when rational integers are close to 1?

Question I've been attempting to resample a GPS signal in MATLAB. I've built a few FIR filters using fvatool and from handmade transfer functions (punched out with ...
1
vote
1answer
92 views

Is there a need of Point interpolation before proceeding for gaussian smoothing of an incomplete distribution?

Suppose there is a distribution that has values sampled on the interval 1-25 with corresponding sample values that have to be smoothed. For example: ...
3
votes
1answer
1k views

Interpolated FIR filter

I am confused about this Q&A : Interpolation by factor of 2 If my input signal $$ x[n]= x0,x1,x2,x3 $$ then according to the threads explaination my $v[n]$ will be $$ v[n]=x0,0,x1,0,x2,0,x3,0 ...
4
votes
3answers
2k views

Interpolation by factor of 2

I want to up-sample my input signal by a factor of $2$. I saw zero padding followed by low pass filter method being used in few cases. But still I need some help in this. Say I have $10$ input ...
1
vote
2answers
774 views

Interpolation vs Interpolation Filter?

Hi guys, I've been reading some papers on - how to remove ghosting artefacts from the Fourier Slice theorem applied to a 3D discrete image volume. The papers mention that in order to remove ghosting ...
0
votes
2answers
414 views

Calculate interbeat intervals

I'm currently reading a paper and I can't seem to make sense of a certain part. A link to the paper: removed The part I don't quite get is on page 286 (after the part where they explain their filters)...