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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22 views

The Proper Way to Do Sinc Upsampling (DFT Upsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples

Given a signal $ \left\{ x [ 0 ], x [ 1 ], ..., x [ N - 1 ] \right\} $ what would be the correct way to upsample it in the frequency domain (Sinc interpolation)? Note: Added as a request by the answer ...
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1answer
89 views

How to change the samplimg rate with interpolation and decimation?

I have a wav file at a 44.1KHz. I'm trying to change the sampling frequency to 1.26MHz. For that, I need to use interpolation and decimation, and so I did, but I'm getting odd results back. It seems ...
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24 views

3D interpolation of a volume with irregular upsampling

Given a collection of 2D slices which as a whole corresponds to a 3D volume (medical image of an organ), I only take specific slices (i.e. I replace the ones I dont want with zeros) and so, I end up ...
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49 views

Interpolation of complex signal

I'm struggling with particular (corner) case of interpolation of complex signal, in connection with OFDM modulation. While I assume that guard sub-carriers are always used, I'm studying a case when ...
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1answer
25 views

Constrained interpolation/smoothing of multi-dimensional time series

Consider an $N$ dimensional time series $x_i(t),~i\in\{0,1,\cdots, N-1\}$ where $x_i(t)$ is smooth. It turns out that for all $t$: $x_i(t)>x_{i-1}(t)$. The multi-dimensional series is sampled at ...
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31 views

Role of oversampling within resampling / pitch modification

I'm working on a pitch modification plugin involving resampling, and want the quality to be as high as possible. I currently use windowed sinc interpolation and lowpass filter where required. I ...
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1answer
48 views

How do I confirm that range cell migration correction was done correctly? Is there a way to check this graphically without looking at the signal data?

I am implementing the Range Doppler Algorithm for a Synthetic Aperture Radar project and I am at the step where I must perform Range Cell Migration Correction. This step involves creating a sinc ...
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1answer
57 views

oQPSK/QPSK conversion with fractional interpolation

I once used a GNU Radio QPSK receiver for oQPSK demodulation. All I did was to "forcefully" delay the Q channel by half the symbol time. At the time, I was using a discrete number of samples ...
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2answers
74 views

Frequency response of discrete time system involving interpolation and resampling

I am working on a problem towards calculating frequency response of discrete time system(does interpolation followed by resampling) which looks like: x(n) is fed to linear interpolator(h(t) = ...
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2answers
127 views

Impulse response of linear interpolation in discrete time

I'm trying to understand interpolation in discrete time. We know that for linear interpolation we use h(t)=triangle waveform. When we talk about linear interpolation in discrete time, I'm using ...
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1answer
72 views

How does upsampling/interpolation/oversampling help with noise shaping?

That's all, Why does upsampling improve the resolution and signal-to-noise ratio? What makes it so good for noise-shaping
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A basic question about bilinear interpolation

I have a basic question about "Bilinear Interpolation". How to derive the bilinear interpolation formula of 4 pixels arranged as follows: And if the bilinear interpolation is applied to ...
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0answers
68 views

Symbol timing recovery: Polyphase vs piecewise linear interpolation

A symbol timing recovery scheme shown below has been successfully implemented in C++. Different TEDs (Mueller & Mueller, Early-Late, Maximum Likelihood, Gardner, Zero-Crossing, etc) are included ...
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65 views

Software implementation of Gardner Loop

My objective is to create a Gardner loop to remove the timing offset present in my signal. To achieve best timing SNR, I downsample my signal to 2 samples per symbol. It is depicted below: where blue ...
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3answers
566 views

Seamless looping of a signal without pops

I'm trying to seamlessly loop an audio signal. When I loop the current audio signal I have, I hear audible clicks or pops right as it loops back to the beginning. I want to be able to loop the audio ...
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3answers
218 views

How to find peak value of an analog signal efficiently after sampling in the digital domain?

I have a bandlimited analog signal for which I want to find the peak value in real time. The signal is sampled and processed digitally at just enough sampling rate. Since the peak of the analog signal ...
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58 views

Eliminating drift generated from double integration of acceleration signal using Envelope Method

I'm trying to remove the drift generated upon the double integration of a noisy acceleration signal. But this question discusses only removing the drift upon single integration to generate velocity ...
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2answers
66 views

Difficulty absorbing Idea of interpolation?

I am trying to develop my understand of interpolation and signal reconstruction and uptill now i have understood that there are 3 commonly studied types of interpolation 1)Zero order hold ...
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1answer
53 views

piecewise-quadratic vs piecewise-cubic vs higher order polynomial interpolation?

There is a question available on DSP SE that mentions types of interpolation used for signal reconstruction but there isn't any mention about the difference between piecewise-quadratic,piecewise-cubic ...
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1answer
198 views

Zero order hold interpolation and Nearest-neighbor interpolation?

Is there any difference between Zero order hold interpolation and Nearest-neighbor interpolation I want to perform zero order hold interpolation in MATLAB,but there isn't any information about zero ...
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1answer
103 views

Streaming windowed sinc interpolation/resampling: trying to understand a Rust implementation

I'm working on a fork of the Rust dasp library, which is intended to be a DSP toolkit that abstracts over samples/frames/signals, and contains a number of functions ...
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58 views

Efficient Method for Interpolating between bins in FFTW

I'm working on some oscillator classes right now and perform FFT around 100 times per second. The issue I'm running into is interpolating between the bins so there is not a noticeable change from each ...
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1answer
30 views

Can multi-rate operations of decimation and interpolation can be used to implement a rate change by a factor an irrational number?

I know that common rates are integer values like 2 or 3, but can multi-rate operations of decimation and interpolation can be used to implement a rate change by a factor of an irrational number? ...
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24 views

Bilinear Interpolation Algorithm for up-sampling 2D images

In keras it is possible to use UpSampling2D layer to up-sample an image. You can use Bilinear Interpolation. Given an image ${h\times w}$ it is possible to increase its size in ${h*k\times w*l}$, ...
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1answer
64 views

Spectral peak location estimation using complex DFT

In this paper a simple method to estimate a spectral peak is proposed, by using quadratic interpolation between three samples of the DFT of the signal. Namely, the position of the peak relative to the ...
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2answers
103 views

Is there a way to use decimation or linear interpolation to shrink or stretch an audio signal in the time domain?

I am able to shrink/stretch an audio signal using Python code for a phase vocoder, as well as the stretchAudio function from Matlab's Audio Toolbox. Although both methods do indeed alter the audio ...
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1answer
47 views

Direct and Transpose Polyphase Multirate Processing

Polyphase implementations of upsampling/ interpolation and downsampling/ decimation, after having invoked the Noble identities, are presented as follows (taken from Proakis): (Three-Channel Polyphase ...
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1answer
82 views

What are some really accurate ways to get the value of a peak (local maximum) given some points around it? (To be used for autocorrelation peaks.)

I have looked everywhere on the internet for this and, surprisingly, haven't found much useful information. Given 3 or more points closest to a peak (local maximum) what are some of the most accurate ...
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1answer
764 views

How to correctly use sinc interpolation in Matlab?

What is the right way to use sinc interpolation for a given discrete signal $x[n]$? Following is the sinc interpolation formula: $$x(t) = \sum_{n=-\infty}^\infty x[n] \mathrm{sinc}\left(\frac{t-nT}{T}\...
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2answers
156 views

HRIR interpolation using VBAP

1) Problem description I am trying to implement a 3D audio simulator in Python. I am using the HUTUBS dataset as HRIR database (more informations here: https://depositonce.tu-berlin.de/handle/11303/...
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1answer
444 views

The Proper Way to Do Sinc Downsampling (DFT Downsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples

Given a signal $ \left\{ x [ 0 ], x [ 1 ], ..., x [ N - 1 ] \right\} $ what would be the correct way to downsample it in the frequency domain (Sinc interpolation)?
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1answer
85 views

Interpolated FIR filter (from Oppenheim and Schafer's Discrete-Time Signal Processing, 3rd ed)

[from Discrete-time Signal Processing by Oppenheim and Schafer, 3rd ed., p.196] Two questions: In this context, the filter with system function represented by Eq. (103) is called an interpolated FIR ...
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After upscaling a signal what noise metric to use for noise qualification

If I have a 2d signal (like image) and interpolate (linear) it to get an upsampled signal, how can I qualify the noise, with which metric? STD changes between the signal and its'upsampled counterpart ...
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30 views

standard deviation of two constant noised signals related through interpolation

Let us say say we have a noised constant signal and want to evaluate the standard deviation (std) of the noise. We calculate the std of the said noised signal and call it $\sigma_1$. Now we process ...
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35 views

Showing that filtering a signal with bandwidth B with a brickwall filter of bandwidth W>B has no effect in time domain

The time-domain representation of $G(f) H(f)$, where $H(f)$ is an ideal brickwall filter of bandwidth $1/(2T)$ is: $$ \int g(\tau) \operatorname{sinc}\left(\frac{t-\tau}{T}\right) d\tau $$ I want to ...
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115 views

minimum oversampling factor for D/A converter

Consider a D/A converter for audio signals consisiting of a zero-order-hold interpolator followed by a continuous-time lowpass filter with positive passband between 0 and 20KHz and stopband starting ...
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2answers
179 views

A cubic interpolation function: folkloric copypasta or clever trade-off?

I've been reading on interpolation methods recently and I have come across an implementation of cubic interpolation that is leaving my head scratching. Every other variant and example of cubic ...
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63 views

Wasn't Wikipedia errata on DFT/Trigonometric interpolation polynomial

https://en.wikipedia.org/wiki/Discrete_Fourier_transform "Trigonometric interpolation polynomial" Section. Shouldn't the middle term in the second line be? $$ \cdots + X_{[(N-1)/2]} e^{i\ ( ...
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2answers
148 views

Efficient double upsampling of a pure real tone

Has anyone seen this trick before? Let's say I'm working with a real pure tone signal that's dangerously close to Nyquist. So, I want to upsample it by a factor of two to move it near the four ...
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3answers
189 views

Why is my time domain interpolation via zero-padding in frequency domain wrong?

Since the process can be applied in either domain to increase the sampling rate in the other domain, I am trying to apply zero-padding in frequency space to recover a 'cleaner' interpolated signal in ...
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1answer
168 views

Frequency response and sampling theorem for triangular function

The triangular function is defined as follows: $h_l(x) = \begin{cases}1-|x|,&|x|<1;\\0&\text{otherwise}.\end{cases}$ According to ccrma.stanford.edu: "If the output of the interpolator ...
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1answer
87 views

Find continuous signal given a condition on its samples

Let $x(t)$ be band-limited with $B = \omega_m$. Sampling gives us $$x(nT_s) = \begin{cases} 1, & n = 0 \\ 0, & n \not = 0 \end{cases}$$ And $\omega_s = 2\omega_m = \frac{2\pi}{T_s}$. Find ...
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2answers
196 views

Why the plots of spline and cubic interpolation are exactly same? [closed]

I am trying to watch difference between cubic interpolation and spline interpolation using matlab plot but i am getting same plots in both cases using interp1 ...
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1answer
39 views

How to transform a signal to go through specific points?

I have a 1d signal obtained using a Fourier based resample method (TDIFDZP) for which the resampled points don't necessarily go through the original samples. I want to transform the upsampled signal ...
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2answers
1k views

Using a low pass filter to interpolate signal

In my DSP university textbook, the interpolation process is described as follows: In order to represent a baseband signal $x[k]$ at an increased sampling rate with the same shapes of its time-...
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0answers
88 views

Zero-padding or Interpolation in 3D FFT

I'm trying to perform a FFT of a 3D regular grid and then compute the bin average (in spherical shell bins) of the Fourier transformed grid. The problem is that the resulted vector is very noisy as I'...
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1answer
88 views

Sinc Interpolation Artifacts

I have written a program that uses sinc interpolation to resample some data. The general algorithm is a that I compute the previous N values and the next N values to get a new sample at a non-integer ...
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1answer
187 views

Determine impulse resonse of First Order Hold (FOH)

Question, how can I determine the impulse response function of a first order hold? On Wikipedia it is simply stated as: $$ h_{\mathrm{FOH}}(t)\,= \frac{1}{h} \mathrm{tri} \left(\frac{t}{h} \right) =...
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3answers
56 views

what are some possible reasons of having duplicates in sensor signal? resulting in stair-step signal?

I am using an cellphone application to record cellphone gyroscope signal. I put the sampling rate to "fastest" which means the highest sampling rate the cellphone is able to do. What is strange is ...
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1answer
106 views

Reconstruction using sinc

The signal that I produce above. What is the reason for it to slide to the right? In oversampling at Nyquist rate can I make like below picture ? do you think the signal i produced at nyquist rate is ...

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