# Questions tagged [downsampling]

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

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### How can I extract the 2 polyphase components of a signal after sampling at the half of sampling rate

Suppose I have a continuous signal x(t), which was sampled using sampling function s(t) whose sampling rate is Ts.How can I sample the continuous signal by Ts/2 instead of Ts in order to get two ...
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### Are oversampling and downsampling the same thing?

According the books I have on DSP, is oversampling, sampling a signal at a much higher samplingrate then normally required, so to reduce the sample-rate (and increase the resolution of the signal) ...
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### Can we sample the signal with any period as long as the Nyquist rate is respected

I have a question regarding the sampling rate. Suppose that we transmitted a signal $m(t)$ then at receiver side, we received the continuous signal $x(t)$, which is time varying and sampled with a ...
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### How can I synchronize signal from an LED and TTL pulses better?

I would like to synchronize my video and voltage data using Python. (I obtain these data using Bonsai and Open Ephys for an open field exploration experiment.) I sent $150\text{ ms}$ long TTL pulses ...
543 views

### Decreasing Sample Rate in DFT (FFT) for Audio Analysis

I'm working with audio data analysis through FFT algorithm. My example audio is a sine wave at 440 Hz and 44100 Hz sampling rate. FFT methods in programming, like ...
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### Downsampling from 100Hz to 60 Hz

I have two sensors measuring a single time varying signal . The first sensor (reference sensor) is sampling the data at 60 Hz and the second sensor (test sensor) is sampling the data at 60 Hz. I ...
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### Downsampling in MATLAB - why scaling filter coefficients?

Trying to undertsand how MATLAB does resampling, looking at toolbox/signal/resample.m. This is the part where (downsampling) filter coefficients are calculated: <...
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### 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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### Downsampling audio for use in Machine Learning

I'm trying to use the work (Neural Networks) done in this repo: https://github.com/jtkim-kaist/VAD It says this: Note: To apply this toolkit to other speech data, the speech data should be ...
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### Multirate Signal processing for matching DAC of the SDR

I have been breaking my head for a long time. Please help with this..any input would be helpful! I am trying to implement a OFDM system using SDR (USRPN210 for Transmitter and USRP2 for receiver) ...
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### What is the effect of the natural logarithm in the frequency domain?

I have read that taking the natural logarithm of a signal $x$ in the time domain will introduce a spectral broadening and hence "up-sampling" process before the logarithm is required. I tried to test ...
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### Downsampling a high pass filter

If I have an ideal high pass filter as the one in the picture: And I downsample it by 2, e.g. $h_{new}[n] = h[2n]$, is my understanding correct that the resulting filter would look like this in the ...
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### Python's $\tt resample$ vs $\tt resample\_poly$ vs $\tt decimate$

I have multiple signals each measured with a sampling rate 300Hz. They are mostly periodic, although there are some parts of some of the signals, that seem to be random and do not follow the rest of ...
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### Explaining a statement regarding aliasing in a document

I am reading this document and in the section "Aliasing and Anti-Aliasing", the author make the following statement: Consider a signal with two frequency components: $f_1 = 10\,\text{Hz}$ which is ...
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### Downsampling and upsampling of a signal in Python

If I want to downsample a signal in Python, is it better to use method resample from SciPy Signal Processing module or method decimate from the same module? What is the difference between these two ...
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### How left out down-sampling in 3D-DWT just on the Z direction

I am working on image processing by a 3D wavelet transform. I have a problem with the classification size of the wavelet coefficients. As you know, when we apply 3D_DWT on the image (for example: ...
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### Image zoom out using Gaussian blur and downsampling

I am trying to implement a simple zoom out algorithm using two steps: The image is blurred using gaussian convolution of standard deviation $0.8\sqrt{{\tt zoomfactor}^2-1}$ as we saw in class. The ...
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### How Is the Bandwidth of an Image Reduced by an Octave in Gaussian Pyramid Procedure?

Reference paper 1. For arguments sake, let's say that the maximum and minimum frequency in an image are 256Hz and 1024Hz. When I perform filtering using the gaussian function, the "bandlimit" reduces ...
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### Downsampling and Convolution: When Can one Swap Between Them?

(Code snippet with example below). In MATLAB, assume I have a long signal vector y (length N) that I wish to convolve with a ...
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### Down sample incoming stream of data to plot a dynamic graph

I am working on a module where I need to plot ECG streaming data on a graph. This graph has configurable speed i.e. plot 1 heartbeat data sample within say 50mm,25mm, etc. For this, I am required to ...
699 views

### Synchronizing signals with different sample rates

I am relatively new to signal processing, so I am still missing some basic knowledge, but I am trying to improve as much as I can. I am trying to synchronize two signals with matlab using cross-...
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### Downsampling: Mathematical derivation

The problem I am having is related to sample rate conversion and more precise to sample rate reduction. I have been working on the paper Interpolation and Decimation of Digital Signals Tutorial Review ...
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### Is FIR decimation the fastest possible method for integer downsampling?

For a digital music synthesizer I am developing, I have a stream of incoming samples $x_i$ and would like to downsample by $M$ to obtain a stream of samples $y_{Mi}$. I am currently bandpassing the ...
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### Downsampling in Matlab simple example

I'm trying to visualise downsampling in the frequency domain in matlab I take a simple sinusoid, perform an fft and plot a two sided spectrum. Then I downsample the time domain signal (...
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### Cut-off frequencies for fractional sample rate adjustment

We have a signal sampled att 22 kHz that we want to interpolate to 40 kHz. So we can do this by upsampling by a factor 20, then downsampling by a factor 11. My question regards the choice of cut-off ...