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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Transmitting data with QPSK using an SDR
My question assumes that I want to transmit some data using QPSK using and SDR.
The SDR will be fed with IQ data and this will transmitted at a sample rate Fs and be up converted to a carrier ...
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LTE PSS Channel Estimation for coarse SSS Equalization
In LTE the Primary Synchronisation Signal (PSS) can be detected by taking a correlation with the known 3 zadoff chu sequences (roots: 25,29,34). Once the peak has been detected the receiver knows ...
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Estimating spectrum with regularly missing samples from data
Suppose:
$$
s(t) = \sin(2\pi{f_0}t)
$$
Suppose I'm sampling the signal with a sample frequency $f_s >2f_0$ .
However, every $M$ samples there is a dead-time of $L$ samples.
Traditionally, the (...
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On FFT, interpolating signal vs extending signal in time
When we interpolate, then FFT the output will have more bins.
When we extend the signal in time, Then FFT output will have more bins too but:
Interpolation increases max bin frequency but time ...
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Frequency spectrum of interpolated sine
When interpolating a sine wave in Python, it seems I get a lot of additional frequencies closely around the fundamental. Why is that the case? I would have expected a more or less similar spectrum, ...
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what degree of accuracy does quadratic interpolation add to fft cross-correlation?
I am not a dsp engineer, so I might be missing some obvious background, but I've been doing my best to educate myself. Let me know if there's more info needed.
I am using an fft cross-correlation ...
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Real time variable speed audio playback with interpolation
I'm trying to correctly implement the real-time variable speed playback of my buffer,
to achieve the pitch shifting.
I don't need to stretch to preserve the original length.
Buffer is calculated with ...
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How can I use interpolation to align audio [duplicate]
I notice that when I connect two audio clips, there is a jump at the junction.
How do I use interpolation to connect these two pieces of audio?
Thanks for the answers, I've got an answer from my ...
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Averaging a Signal with a delayed version of itself
I am working on a problem that requires interpolating between two music files. One music file is very similar to a delayed version of the other.
I would like the 'average' of the two signals to sound ...
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Sample rate change using Lagrange interpolator
I'm trying to understand how to make Sample rate change by a non integer factor say $K=1.0012$
In real hardware I will be using cubic polynomial but for now I have chosen a linear interpolator. I have ...
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Correct OFDM oversampling method
I need to oversample my OFDM signal, however I have issues understanding which OFDM oversampling method is the recommended one.
First method :
Before taking the IFFT, the OFDM subcarriers are padded ...
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DSP library for Software Defined Radio
Can anyone recommend a good C library for SDR? To be more specific I just need a function in C to compute coefficients for CIC compensation filter (I need to do it in real time, so Matlab is not an ...
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How can the DCT be used for bandlimited interpolation?
I know the discrete cosine transform (DCT) is used for compression, but can anyone give an example of how to use it for bandlimited interpolation?
One way might be zero-padding in the DCT domain and ...
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Why does interpolation with zeros introduce frequency artifacts?
Consider the original signal (just a sine) and the same signal interpolated with zeros:
The Fourier transform of them:
In this example I inserted only one zero between the samples, as if I sampled ...
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Upsampled signal values
My question is: after upsampling a signal, does the output signal contain the original signal values? The diagrams I saw so far (on wikipedia and different forums) have always shown the original ...
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Resampling in time
I have a huge dataset, way too much to be loaded into memory. I need to downsample the data to a new rate. Normally, this would consist of upsampling by N, applying FIR LPF, then decimating by M to ...
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Multiple questions about how to implement practical resampling
I am learning resampling theory, and for the time being I am specifically interested in downsampling. I have a textbook that is not a dsp textbook but has a section on resampling. The way they put it, ...
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How should I interpolate on a triangle mesh?
I have a triangular mesh (generated from a Lidar point cloud).
On this mesh I do point measurements using two instruments. One records M amplitudes of frequencies in the visible range and the other ...
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Does the combined pointsample+bilinear upscaling algorithm have a name?
I have been performing digital image upscaling of pixel art in one of my hobby projects, and the two simplest upscaling algorithms are point sampling or bilinear upscaling.
Point sampling exhibits ...
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Are there ways to reduce the smearing of zero-padding interpolated data?
Are there ways to reduce the smearing / spectral leakage of zero-padding interpolated data?
I learned that, given a small collection of samples, one can increase the frequency resolution of an FFT ...
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Reconstructing an undersampled signal by cutting off at the signal's maximum frequency
Assume a (continuous) band-limited signal $f$, that is, a signal for which $F(s) = 0$ for all $\lvert s \rvert > p / 2$.
If the signal is sampled with frequency $p$,
we can reconstruct it by ...
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Accurate frequency estimation with closely-spaced tones
I have a MIPs-limited DSP platform where I am taking an FFT of a streaming audio signal at regular intervals. I need to find the top 4 amplitude peaks and their corresponding frequency for every frame....
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Extract diagonal area from image
I have a gray scale image of fibres in different orientations. My goal is to mark the area where the fibres have a specific angle and neglect the rest. In the future it should be an automated process ...
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Spline interpolation of a binary mask
I have the following binary mask (If it helps you can assume that every it is always 1px wide).
I want to travel from one given point to another (from start to end in this case). You are given the ...
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Zero padding versus zero stuffing
Let's say I want to increase the sampling rate of my signal, $f_t$, from a sampling frequency $f_s$ to some multiple $Mf_s$. One way to do this is to add zeros between the samples of $f_t$. This ...
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Interpolation to create equally spaced value using Python
I am working on a project in which I am required to use Interpolation to create equally spaced position values as the position samples are not equally spaced due to varying train speed.
So, the total ...
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Applying Kaiser Window to sinc interpolation
I am trying to apply the kaiser window during sinc interpolation.
The following is my sinc interpolation code:
...
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16 point Sinc Interpolation Kernel
I have a signal that is sampled at Fs and wish to apply a "16-point Sinc interpolation kernel". However, I am not sure what the 16-point refers to. Does it refer to having a kernel that is ...
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Multirate Control System Transfer Functions
I'm interested in oversampling the inputs to a digital controller to increase the SNR of the input process variable signal. I've read on this site and in articles like the one below that it is not ...
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How to interpolate the peak amplitude of an fft output?
I want to find the peak amplitude of an audio signal in a given frequency area.
My problem is that if the signal has a strong resonating frequency between 2 fft bins, then both bins are way below the ...
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Odd artifacts after sinc interpolation
I am trying to upsample a signal using sinc interpolation. I have written a way to do this in python.
...
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Guided bilinear interpolation: is it a known algorithm?
I have a function that's sampled relatively coarsely along one direction, $x$, and much more finely along another, $y$. Sampling grid is regular. I need to interpolate between all these samples, with ...
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Basics of interpolation: is filter or upsample first?
I am studying interpolation filters. I'm under the impression that when talking about interpolating a signal, we filter and then upsample the signal.
BUT
In an article, Interpolation (Digital Filter ...
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Interpolate & sample period GNU Radio
I've a little question regarding interpolation in GNU Radio:
I'd like to do an interpolation (by a factor of 2) and be able to change the sampling period of the samples interpolated but im having a ...
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Fractional Frequency Shifting a Discrete Signal in the Frequency Domain
In our current hardware-based signal processing pipeline, we have a time-domain signal $x[n]$ that we want to frequency shift by $f_0$. To do this, we multiply the signal by a complex exponential in ...
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Plotting the Frequency Response of Zero-Order Hold
I'm trying to find the frequency response and the DC gain, then plot the response and find the cutoff frequency from the graph.
I start off with the impulse response
$$h(t)= 1 ; 0\leqslant t\leqslant ...
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Why is this Python implementation of trigonometric interpolation not working properly?
Consider a signal $u_j, j = 0, 1, \dots, N-1,$ sampled on an evenly-spaced grid of points, $x_j$. Define the discrete Fourier transform of $u_j$ by
$$U_k := \frac{1}{\sqrt{N}} \sum_{j=0}^{N-1}u_je^{-(...
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Performing Sample-Rate Conversion on Subchunks of an Audio Signal
I have implemented sample-rate conversion (SRC) from scratch in my hobby music player, and it worked fine. However, originally, the music player loaded entire audio files into memory and performed the ...
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Symbol Timing Recovery with Fractional Sample per Second
I'm trying to write symbol timing recovery loop and taking help from "Digital Communications A Discrete-Time Approach" by Miachel Rice. MATLAB communication toolbox has also implemented the ...
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How to implement interpolation by convolution for rotation of an image by an angle which is not a multiple of 90 degrees?
I know that the usual way to perform rotation of an image is to compute the new pixel coordinates by multiplying with a rotation matrix $ \begin{pmatrix}x_{rot} \\ y_{rot} \end{pmatrix} = \begin{...
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Why does upsampling and interpolation by convolution introduce a shift compared to imresize?
For purposes of understanding the process - not for any practical purpose for which I could use imresize - I wanted to show that 2x upsampling followed by convolution with an appropriate kernel (...
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Good interpolation functions for downscaling magnitude spectrums
I'm trying to downscale a 1D FFT (for displaying an audio spectrogram, like this:
My question is: assuming I have a 512 bands spectrum, what would be the recommended interpolation algorithm to ...
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Resample signal and start from a different point with numpy.interp
I am trying to resample a signal in Python, only by giving the new and the old step. My function works fine until here.
But now I want to start the resampled signal at a specific point other than the ...
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Interpolation FIR filter output spectrum
I've inherited some FPGA code implementing an interpolation by 2 with a FIR low pass filter. The code came with a cocotb test bench that also models a filter (scipy.signal.lfilter) and then compares ...
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Sinc Based Multi Dimension Signal Resampling on the Fourier Spectrum (DFT)
As a generalization of the following questions:
The Proper Way to Do Sinc Downsampling (DFT Downsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples.
The Proper Way to Do ...
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Applying 2D Sinc Interpolation for Downsampling in the Fourier Domain (DFT / FFT)
Related to The Proper Way to Do Sinc Downsampling (DFT Downsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples, how can one apply Sinc downsampling in the DFT / FFT domain ...
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How to Find the Kernel of the Convolution for Linear Interpolation?
I'm trying to solve the following exercise:
Image A was doubled by linear interpolation. The magnification was performed in two stages. In the first stage, add about zero pixel to the image between ...
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Applying 2D Sinc Interpolation for Upsampling in the Fourier Domain (DFT / FFT)
Related to The Proper Way to Do Sinc Upsampling (DFT Upsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples, how can one apply Sinc upsampling in the DFT / FFT domain for a ...
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Downsampling an image using sinc interpolation?
I have a discrete image of size $2^N \times 2^N$ which I would like to iteratively downsample to produce a pyramid with image sizes $2^k\times 2^k, \, k=0,\ldots,N$. That is, each subsequent image ...
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1D Interpolating subdivision for wavelet lifting schemes
I am looking into wavelet lifting methods first introduced by Swelden, and explained in this paper: Build your own wavelets at home.
In this paper (in chapter 2 specifically), they discuss ...
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