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Questions tagged [downsampling]

In signal processing, downsampling (or "subsampling") is the process of reducing the sampling rate of a signal.

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Multirate systems - downsampling

As my teacher explained the process in class, I wanted to write a MATLAB code for learning purposes that downsamples a signal with a downsampling factor of L. Here's the code I wrote and the output ...
minghierid's user avatar
1 vote
1 answer
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call decimate function from matlab

I tried to call decimate function in Scipy from Matlab but met an error. Can somebody point me in a direction, please? Here is a code of Matlab ...
Jingdong Zhang's user avatar
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Pixel Shift when using Fourier Downsampling

I am working on a Super-Resolution network, and want to try to use Fourier downsampling, different from the normally used bicubic downsampling as it relates to MRI imaging. I have tried using this ...
Christoffer Overgaard's user avatar
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Downsampling of signal

I have two signals, for example, $x_1[n]$ and $x_2[n]$, which are the same for every $n$ except for $n_0$ and $n_1$. They are both bounded within a frequency range of $\pi/3$. I want to reconstruct $...
Moran Poco's user avatar
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2 answers
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Benefit of Anti-Aliasing for Wideband Finite Time Duration Signals prior to Sampling

Most literature about sampling explains the need for anti-alias filters in terms of periodic signals, preventing a periodic signal with frequency greater than half the sampling frequency from ...
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Effect of aliasing on time-domain SNR

I'm trying to reconcile the fact that decimation without low-pass filtering does not modify the ratio of signal to interference power in the time domain with the fact that, in the frequency domain, ...
Roger's user avatar
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Simulating 32x32 Radar Configuration from 64x64 FMCW Radar Data

I have gathered data using an FMCW Radar with a configuration of 64 chirps per frame and 64 samples per chirp. Now, I'm trying to simulate the data as if it were collected by a radar with a 32x32 ...
Eric's user avatar
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4 votes
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FIR filtering a limited subband of a signal

I have a full band audio signal (sampled at 48000Hz) and I want to process only the low frequencies with an FIR filter. The maximum frequency that I need to process with the FIR is 3000Hz, i.e., an ...
Florent's user avatar
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Is indexing of color independent from pixel sampling, or do they interact, and how?

My partner stitches, and uses sites like https://www.pixel-stitch.net/ in order to produce patterns. These sites do two things: they downsample an image in space to produce fewer pixels, but they also ...
Nikolas Skoufis's user avatar
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1 answer
81 views

What is the best method of describing the effects of downsampling on a chromatographic signal?

I am in the process of compressing a set of chromatograms to develop a preprocessing pipeline, that will end with DTW for peak alignment. During this process I have downsampled a signal from 0.4 ...
jstathakis's user avatar
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Is this proof valid?

Consider a discrete-time sequence, $y[n]$, defined as: $$y[n] = \frac 12 x[n] + \frac 12 (-1)^n\: x[n]$$ where $x[n]$ is another discrete-time sequence. The DTFT of $y[n]$ defined as $Y(e^{j\omega}) = ...
Ahsan Yousaf's user avatar
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Lowpass filter to downsample data

I have some data that is sampled at a certain rate (16384Hz). I am only interested in the 10-30Hz region, so I want to downsample the data. My idea to do this goes as follows: I apply some kind of ...
sancholp's user avatar
1 vote
1 answer
300 views

How does downsampling decrease the noise power?

I read one equation from a technical document, i.e., assuming the time-domain white Gaussian noise samples with variance $\sigma_{TD}^{2}$ in dB are sampled using ADC with sampling rate $f_{s}^{ADC}$, ...
Vic's user avatar
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Does SDR configured with low sample rate automatically averages samples?

This is probably a basic question but I didn't find any answer online. Suppose we configure a SDR (least say, with a maximum sample rate of 100 Msamples/s) with a low sample rate (e.g. 1 Msample/s). ...
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How to calculate phase rotation of I/Q reference samples for Bluetooth Angle of Arrival

I am trying to compensate phase rotation due to carrier frequency offset (CFO) for Bluetooth Low energy (BLE) Angle of Arrival (AoA). In BLE AoA the adv. packets carry a Constante tone extension @...
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2 answers
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Is downsampling LTI for bandlimited inputs?

This question stems from the discussion we had on a previous question of mine. The point of contention is whether the downsampling operator is time invariant or not. Which gives us a new condition to ...
Ahsan Yousaf's user avatar
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Is the following system LTI and what is its purpose?

Above is a block diagram of a discrete-time system $T\{x[n]\} = y[n]$. Here, $h[n]$ is the impulse response of an arbitrary LTI system. Firstly, is this overall system LTI? I don't think so because ...
Ahsan Yousaf's user avatar
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Can we do down sampling by taking fft, omitting samples on the ends of the spectrum, and then taking inverse fft?

Suppose that we have a signal with a length of 4096 and want to down sample it by a factor of 2 and obtain a signal with a length of 2048. Suppose that the the maximum frequency content of the signal ...
alireza's user avatar
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Is this how to show decimation in the frequency domain?

Let's say I have a discrete-time signal $y[n]$ that is passed through an Ideal Lowpass Filter (impulse response $h[n]$) to get $y_1[n]$. The filter has cutoff frequencies at $\pm \pi/N$ rad. Now this $...
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Summarization of audio in frequency domain?

I need to summarize a set of samples representing an audio to achieve a smooth zoom animation for a spectrogram in my app. In the time domain (waveform) I achieve this by resummarizing the samples ...
Baffo rasta's user avatar
4 votes
2 answers
797 views

How is the DFT involved in downsampling?

I recently had my first proper class of DSP and upon completing the review of Signals and Systems my professor started working on the concepts of upsampling and downsampling. Of course as is their ...
Ahsan Yousaf's user avatar
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0 votes
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274 views

Effect of FIR filter on the time resolution of the signal

Let's say I have a noisy raw signal with 1GS/s sampling rate (That means the time resolution is 1 ns). Now I apply a FIR lowpass filter (window filter) of 25 MHz on it. The length of Window filter ...
Ayir's user avatar
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Frequency constraints on a down-sampled signal

I am preparing for an examination and am confused about one of the questions on the study guide. The question given on the study guide is given below. We want to implement a change of sampling rate ...
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Observed Maximum Frequency Not Expected For Given Sample Rate

I'm downsampling a given .wav from 44100 to 22050 samples/second. When I play it back I'm looking at the signal with an EQ, and I would expect that I wouldn't see any content above ~11k. However, I ...
Valevalorin's user avatar
1 vote
1 answer
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Symmetric half band filter - redundant oversampling?

I'm making a basic symmetric decimating half band filter (M=2), with alternating 0 coefficients. The signal is oversampled by a factor of 2, at frequency $f$. I must be missing something simple, but ...
awjlogan's user avatar
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4 votes
1 answer
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The Effect of the Order of Downsampling and Smoothing on the Output

How do I prove or disprove: Smoothing an image with a 3x3 filter using full convolution and then downsampling an image by 2 produces the same result as downsampling an image by 2 and then applying ...
Kumar's user avatar
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6 votes
3 answers
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Moving average before downsampling: effect on Nyquist frequency?

First the simple questions: Is there an effect on the Nyquist frequency when I apply a moving average filter on the raw data before I downsample? And what does this do to aliased frequencies? ...
W_vH's user avatar
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2 answers
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Downsample (aggregate) raster by a non-integer factor, using a Gaussian filter kernel

The task is to downsample (aggregate) a raster from 100m pixel size to 460m. The aggregation should be performed using a Gaussian filter. To better understand the task, I am following the paper ‘The ...
Nikos's user avatar
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Why use sinc function to downsample an image in fourier domain?

I'm very confused about downsampling in image processing and the use of sinc function to do it. I read this post [1]: 2D Fourier downsampling some time ago that talked about my own doubt, that is to ...
overflow''s user avatar
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Downsampling a binary file

TEXBAT is a recorded dataset about spoofing scenarios for evaluating GPS signal authentication techniques. On this project, there are recorded GPS signals stored as complex 16- bit samples at a rate ...
Aldrich Taylor's user avatar
5 votes
1 answer
861 views

Polyphase Decimation Filter parallel inputs

I have an FPGA that's streaming in samples from a high speed ADC. The FPGA clock rate cannot run at the sample rate, so the samples are streamed in parallel (4 samples per clock cycle). I'd like to ...
Sittin Hawk's user avatar
7 votes
2 answers
2k views

Downsample a signal by a non-integer factor

I have a signal with a sample rate of 8.9286 MHz and I want to downsample it to 500 kHz. Since 8.9286 is not an integer multiple of 0.5 I can't simply decimate. Which downsample techniques are ...
Ivo Tebexreni's user avatar
1 vote
1 answer
249 views

Does downsampling an image twice result in a "worse" (or different) image than downsampling once

I am working on a project where the input is a large high quality image (2560 x 1440 pixels), which is eventually scaled down a lot (256 x 256) and used as input to an ML model. For reasons that I won'...
Gordon Bailey's user avatar
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1 answer
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reconstruct the low resolution signal before upsampling

When we upsampling a discrete 1d signal by 2x, we first interleave the signal by 0 and add zero padding, then pass through a low pass filter. low resolution signal [x1, x2, x3, x4] -> interleave 0 ...
Zongze Wu's user avatar
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1 answer
370 views

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 ...
Eric Johnson's user avatar
0 votes
1 answer
298 views

question about time delay of practical filter design with sampling frequency

most system have 48khz and if i have 40tap low pass fir filter that cutoff freuqency is 300hz, filter delay is 1/48000*20 = 0.0004s but the frequency resolution is very sparse and i think if the ...
gg h's user avatar
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3 votes
1 answer
486 views

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 ...
lightxbulb's user avatar
2 votes
1 answer
100 views

Noise from irregular sampling pattern

In this paper the author says By using an irregular sampling pattern and filtering the irregular samples to create the pixels, featureless noise is produced from such high frequencies rather than ...
a piece of something's user avatar
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1 answer
326 views

spectrogram of a (strongly) downsampled file

I downsampled an audio file to a very low sampling rate, 48hz. This is because I stored some information in the file, that are not really audio information but the audio format was convenient to use. ...
buscon's user avatar
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0 votes
2 answers
275 views

when is downsampling followed by upsampling shift invariant

i have a set of images that i need to send through an hourglass-type convolutional system. I understand convolutions are shift-invariant, so i will ignore them the question is then: If I downsample a ...
Anatoly's user avatar
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0 votes
1 answer
254 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 ...
yarin Cohen's user avatar
1 vote
1 answer
171 views

EEG peaks do not get identified at the correct frequencies

For my thesis I am re-analyzing a dataset where subjects were visually stimulated with 5.45, 8.57, 12 or 15 Hz. This well-known technique (steady state visual evoked potential) should elicit EEG peaks ...
Pelskens's user avatar
0 votes
1 answer
207 views

What's the correct way to align two signals downsampled at 10 Hz?

I'm trying to build a dataset where one of the features is a signal which has originally been sampled at 500 Hz, while another feature is a signal which was sampled at 100 Hz. I want to downsample ...
ИванКарамазов's user avatar
6 votes
1 answer
2k views

Appropriate Gaussian filter parameters when resizing image

When scaling an image down it is common to first convolve the image with a Gaussian filter. Given a scale factor $0 < s < 1,$ what is an appropriate $\sigma$ to use? For example, if $s = 0.5$ (...
wcochran's user avatar
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1 vote
1 answer
579 views

Downsampling( decimation) theory: additional frequency

I work on a simulation decimation filter: downsampling + filter. My test environment: low data rate receiver, BPSK, square root raised cosine filter with cutoff frequency =0.5, transition bandwidth = ...
LeeLeeYa's user avatar
2 votes
3 answers
452 views

Is there any deterministic downsampling algorithm for audio?

I was trying to use the scipy.decimate function provided in the library, but I had a question - I want a pre-processing algorithm to downsample audio in such a way ...
neel g's user avatar
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In repeated upsampleing and downsampling by 2, how do i calculate the output Y(z)?

For example, if X(z) -> {downsampled by 2} -> {upsampled by 2} -> Y(z) Given that: X(z) = 1+z^2+z^12+z^19 How do I compute the value of Y(z)?
roman numerals's user avatar
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574 views

Rate transition block in simulink

My model is operating at a sampling interval of $\frac{1}{f_0 \times N \times L_{maf}}$ s, (using a fixed point iterative method), now i want the output of my model to be at a sampling rate of $ f_0 \...
mka_07's user avatar
  • 15
3 votes
2 answers
159 views

Image downscaling methods

I am researching downscaling methods for image downscaling. I've both read and found area-averaging to work well in Python using CV2, but the settings in MATLAB allow for it's bicubic interpolation ...
Dalton's user avatar
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1 vote
0 answers
40 views

Dynamic sampling of thermal images

My master’s dissertation subject is to analyze and implement an algorithm that would sample (store) thermal images from camera with different frequency rates to optimize database size and processing ...
Andre's user avatar
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