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Questions tagged [interpolation]

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

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difficulties implementing windowed sinc interpolation (C++)

I'm currently trying to implement a windowed sinc interpolation. I've already written some code for that, but it only seems to work for cases where phaseInc <= 1.0 (phaseInc = outSampleRate / ...
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2answers
69 views

Frequency response of numerical differentiation by polynomial interpolation / finite difference

One can use polynomial interpolation (or finite difference) to do numerical differentiation. However, there seems to be a surprising lack of interest in obtaining frequency response of this numerical ...
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25 views

Isosurfaces from three dimensional column data: methods

I have just been asked the following question, and I somehow felt short of smart answers. You are given a series of $N$ triplets of values ($P_1$, $P_2$, $P_3$), pertaining to physical measurements. ...
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Interpolation of audio for new frames

I am trying to upsample a video by existing frame interpolation techniques. In the process, I realize that I also need to interpolate the audio signal for the new frames so that the audio signal is in ...
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57 views

Upsampling signal using convolution-based interpolation filters

I am currently reading this paper which discusses several image interpolation methods, such as nearest neighbor and linear interpolation, using convolution filters. I first want to do this in 1D with ...
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1answer
27 views

Having Glitches trying to use a Sinc Function Interpolation on a Signal, by chunks of 1024 samples

I am trying to interpolate a signal using a third party lib that performs Sinc Function Interpolation on a signal. It works well if I input all the samples at once but introduce phase distortion if I ...
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Efficient computation by interpolation for CLAHE algorithm

I'm trying to understand how CLAHE algorithm works and i am stuck in the interpolation part of the algorithm. This link: https://en.wikipedia.org/wiki/Adaptive_histogram_equalization tries to explain ...
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1answer
32 views

Why is interpolation a time varying system

I was reading about interpolation (Interpolation and Decimation of Digital Signals - A tutorial Review, Ronald E. Crochiere) and found that Interpolation filter is a time varying system. Can someone ...
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27 views

Interpolation of missing audio signal in a video sequence

Suppose there is a video sequence and there are some frames for which the audio data is missing. I want to interpolate the missing audio data on the basis of the correlation of the audio signal with ...
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1answer
51 views

Bilinear interpolation implemented by convolution

I read the paper Deep Feature Flow for Video Recognition https://arxiv.org/abs/1611.07715. In Sec.3, the author implements bilinear interpolation like this: $$f_i^c(p)=\sum\limits_{q}G(q,p+\delta p)...
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89 views

Low pass filtering of an upsampled(zero inserted) signal

I have been working on interpolation in python from quite some time. The input signal is a sinusoid signal sampled at 933KHz. I am upsampling the signal by a factor of 5 and later using an FIR ...
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1answer
136 views

Implementation of a Variable Fractional Delay with Lagrange Interpolation using Farrow Structure

I am writing a C++ simulation software working in time domain. I generate regularly sampled data, and need them to be delayed, in "real-time", by a variable fractional delay. This is a pretty common ...
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Correlation between elements of a video

Should there be an expected correlation between the audio signal and the frame pixel data, considering the frames of a video? If so, what is the reason for such correlation? Pondering over the topic ...
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Wiener Filter: spacing of the data

I read in an article that for the discrete version of Wiener filter as proposed by Levinson, the data can be arbitrarily spaced. What is implied by this? I believe that the spacing does matter to ...
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1answer
30 views

Question on Levinson's proposed discrete form of Wiener filter

The whole foundation of Levinson's discrete version of Wiener filter is based on the assumption of stationarity of a time series, and aims to predict a value based on the past observed values. Now, if ...
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54 views

Difference between 2D image resampling and 1D signal resampling

I implemented a rational resampler for 2D bitmap images by the following steps: Zero-stuff to interpolate Low-pass filter to remove high frequencies introduced by zero-stuffing Low-pass filter to ...
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Question on stationarity of a time series

The whole foundation of discrete Wiener theory for estimation of signals, leading to the Yule-Walker equations assumes stationarity of the time series. But, financial data, in general, may not be ...
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47 views

Resampling or interpolating non-uniform 2D measurements

I am not sure what I should call what I am looking for, but I have some measurements that have 2 independent variables and I would like to get an interpolated value at a specified x,y coordinate. My ...
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Exploiting coefficients symmetry of a FIR interpolation filter in a polyphase implementation

I'm trying to figure out whether there is a way to exploit a symmetry of a FIR interpolation filter in a polyphase implementation. I know for a fact that we can exploit the symmetry in a normal FIR ...
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1answer
31 views

What is the right way to interpolate a 2D grid?

Let's say I have a 2D grid of temperature measurements in some area and I want to estimate the temperature at some point between the samples. Or at every point, which would basically amount to ...
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31 views

Simultaneously interpolating and smoothing a 1D signal

I have an array of $(x,y)$ coordinates which represents the trajectory of an object in time. The coordinate values are, in general, quite well-behaved in the sense that there aren't many outliers, but ...
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2answers
55 views

Image Interpolation Using the Yule Walker Equations

I have been studying about the Yule-Walker equations for prediction of a time series data from knowledge of past values of the series. Is there any way I can use the same in an image to exploit the ...
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1answer
58 views

interpolate 1D signal depending on 3D parameter space

I have a 1D array of data d(x,p) in which a number of "bumps" or "dips" appear and/or move in the spacial dimension x, depending ...
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2answers
81 views

Radix2 fft - zero padding output size

With zeros padding the FFT radix2 has different input size than output. How to deal with that? I see two solutions but not sure which one is better/appropriate. Maybe you know some other and better ...
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Implementation of halfband pass filter

I need to interpolate a complex valued bandlimited periodic function using local interpolation. I can have the signal sampled at any frequency I want over at equispace intervals. I am aware that for ...
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1answer
191 views

Interpolated FIR filter group delay

I'm trying to design a digital low pass filter with a narrow transition band. My sampling rate is 25 kHz, the cut off frequency is 60 Hz & the transition band width is 4 Hz. I'm looking for about ...
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1answer
65 views

Online interpolation of temporal signal

I have a signal generated from an accelerometer, what I want to do is to receive the incoming signal and check if it is in a certain interval, if it is then I can apply interpolation on it(but ...
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2answers
596 views

How does nearest neighbour, bilinear and cubic interpolation work in images?

More math is appreciated for each of the methods and references are appreciated. I have tried understanding from Wiki and matlab link but don't understand how the translation matrix is being used ...
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1answer
208 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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3answers
102 views

Detect the beginning of an increasing signal

After denoising and cleaning, I get amplitude signals like this (y-axis: dB): On bottom left of each of these 3 graphs, you can see a noise floor (nearly "horizontal line"). This noise floor ...
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1answer
83 views

Relationship between interpolation accuracy, impulse response and frequency response

Global interpolation or sinc interpolation is an ideal filter since its frequency response is a rect function. The impulse response of this filter is the sinc function (same as the coefficients of the ...
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Resampling nonuniform data by linear interpolation [duplicate]

Let's assume that we have data that has nonuniform samplerate. 13,2 22,3 47,8 Above we have values 2, 3 and 8 at time 13, 22 and 47. We want to have samplerate ...
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53 views

Oscillator resynthesis with interpolated phase in sinusoidal model

I'm implementing a sinusoidal model based on the STFT of an input signal: Analysis occurs at evenly spaced hops of S samples; spectral peaks are tracked and the peaks of analysis frame m are matched ...
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1answer
274 views

Sample Rate Conversion between 32K and 44.1K

I would like to know what are possible/typical efficient implementations (preferably in fixed-point DSP) of synchronous sample rate conversion between 32KHz and 44.1KHz (audio applications). Also, I'd ...
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2answers
263 views

Interpolation and decimation

I have a sinusoid in continuous time, with a frequency of 18kHz, it is sampled ideally with a continuous to discrete convertor, with a frequency of 27kHz. After that, we change the sampling speed in ...
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FFT max values interpolation

I'm pretty new in signal processing and need you support. I'm trying try to understand and to find a possibility in Octave or Python how to interpolate or just plot a curves of FFT max values(see pic ...
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1answer
196 views

How to smooth (or interpolate) phase of FFT and reduce data points

I am writing some code for audio analysis, and have currently got two signals with FFT performed on them. I get the phase of my complex array by using: ...
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1answer
46 views

Most natural interpolation to simulate increasing distance?

Background: I'm generating multiple datasets with varying scales of resolution to simulate taking pictures from varying distances and then comparing image classification performances. For example ...
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0answers
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Impact of Interpolation Types in Image Filtering(SOLVED)

I am trying to construct Laplacian pyramids with different interpolation schemes such as bilinear, nearest neighbor, cubic and spline to observe the effect of interpolation types. I wrote a code in ...
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Is the higher order spline interpolation better than the cubic spline interpolation? [duplicate]

i am so confused with the accuracy of the spline interpolation. if higher order spline is better, then please do mention the examples. thank you!
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Playrate change based on sinc interpolation generating phase shift?

I want to simulate the play-rate change function of a modern digital sampler. For the purpose I have constructed a sinc-resampling based algorithm of my own which changes the play-rate of a digital ...
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1answer
92 views

Spectral density interpolation: Applications?

Let $\Phi_1$ and $\Phi_2$ be two matrix-valued power spectral densities. I wonder whether the problem of interpolating $\Phi_1$ and $\Phi_2$ has been studied in the literature and/or applied in ...
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2answers
134 views

Interpolation techniques for extremely limited hardware

I am trying to playback samples on a retro-computer. The hardware is extremely limited, so I am forced to use software PWM as my main method of playback. The limitations of the platform mean that I ...
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2answers
410 views

Interpolating the peak of a cross-correlation using a centroid

Forgive me if this question is poorly worded, I'm not sure if centroid is the word to use here. Say I want to interpolate the peak of a cross-correlation function in order to get sub-sample delays. I ...
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1answer
77 views

Advantage of complex filtering in multirate applications

I've seen it mentioned in passing in various papers on signal processing and filter design that complex FOR filters can be more efficient when it comes to multirate applications. However I cannot ...
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0answers
124 views

Software based synchronizing of multiple data streams/sensors with slightly differing sampling rates

Situation: I try to synchronize the data streams of multiple sensors (ADXL372) of the same type but with different data output rates. The data sheet states all sensors should have the same sampling ...
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0answers
2k views

Design of a Butterworth lowpass filter in MATLAB

I'm using the Signal Processing Toolbox in MATLAB to design a Butterworth low-pass filter. I'm told that my filter has been giving some unexpected results. In particular, when the values from this ...
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5answers
2k views

Effects of linear interpolation of a time series on its frequency spectrum

Situation In order to synchonisize different time series i have to apply linear interpolation on them. After the interpolation and synchronization the signal is transferred into its frequency domain ...
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88 views

STFT Gaussian Window LQIFFT method

I'm trying to learn more about STFT in a analysis perspective. In order to get a good frequency estimation of a signal, it seems that interpolating the magnitude of adjacent bin is a good way. ...
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79 views

How to reconstruct/resample/interpolate a 3D signal using convolution

Assuming we have a sampled 1D signal and we want to upsample/resample, then we add 0 values inbetween the existing samples and then do convolution with a reconstruction filter e.g. $H(s) = [0.5, 1, 0....