# Questions tagged [downsampling]

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

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### 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'...
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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 ...
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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 ...
57 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 ...
90 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 ...
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### 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 ...
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### 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. ...
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### 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 ...
101 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 ...
63 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 ...
67 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 ...
371 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 $s = 0.5$ (...
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### 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 = ...
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### 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 ...
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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)?
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### Loosing information in decimation - without aliasing

We sample each other sample (01010101). Now say we have a signal - that is inside the original sample which has the pattern of (010-1). Decimation gives us 000 for this sub-signal. How to prove this ...
1 vote