Questions tagged [downsampling]
In signal processing, downsampling (or "subsampling") is the process of reducing the sampling rate of a signal.
188
questions
1
vote
1answer
48 views
number of multiplications per second required by the system
Consider a system implementing a rational sampling rate change by 5/7: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency π/7 and a downsampler by 7. The lowpass filter is a ...
0
votes
1answer
30 views
Can you downsample unevenly with even distribution?
Could I downsample a series of length 10 to length 7, with even distribution?
i.e. Numbers get split across two (neighbouring) resultant numbers, as opposed to one result being a combination of 1 ...
0
votes
1answer
81 views
the number of multiplications per second required by the system
Q1. Consider a system implementing a rational sampling rate change by 5/7: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency π/7 and a downsampler by 7. The lowpass filter is ...
0
votes
1answer
39 views
The impact on the frequency of adding zero samples and non zero samples
Can someone give me a brief explanation of what is going on in here? I struggle to understand the full differences between the impact on the frequency of added zero samples and adding samples which ...
0
votes
0answers
22 views
Adding zeroes in between the samples of a discrete frequency domain leads to both zero padding and scaling
I won’t show ALL the calculations, but I’ll describe the problem fairly enough to understand.
We’ve been taught that upsampling on one domain leads to padding zeroes or added time period which is zero ...
2
votes
1answer
164 views
Downsampling and low pass filtering in one step?
Image pyramids are created by applying a lowpass filter (Gaussian) and then decimating the image (keeping only every n'th sample).
In The Pyramid as a Structure for Efficient Computation the start ...
-1
votes
1answer
104 views
How do I generate a smaller DFT result?
I have a very large input that I'm Fourier-transforming. Currently, I transform the entire signal and then downsample the result. Although the transform of the large input is expensive, my results ...
0
votes
0answers
19 views
Bandpass filter is not working as expected
The sampling rate that I have currently is at 384kHz and I want to downsample it down to 44.1kHz. I want to use a bandpass from 5kHz to 200kHz but I am only able to bandpass up to 192kHz for some ...
0
votes
0answers
34 views
Can largest-triangle-three-buckets downsampling method used with fourier transformed signal?
I've been reading on the largest-triangle-three-buckets downsampling method for downsampling. Though it was originally published in the thesis "Downsampling Time Series for
Visual Representation&...
1
vote
1answer
28 views
DTFT and a Downsampled Sinc Function
I found the answers to this question and this question to be extremely helpful in understanding the derivation of the downsampling or decimation property of the DTFT. Thank you! I am now struggling ...
1
vote
2answers
72 views
Decimation Question about using a low pass filter before downsampling
I have a bunch of audio files that have a sample rate of 380kHz, however I would like to reduce this sampling rate to 44.1kHz. From doing some research online, it seems like I will have to use a low ...
0
votes
0answers
9 views
How to choose the appropriate number of samples for discrete wavelet transform denoising?
I want to make sure I am understanding the filter bank frequencies correctly in DWT decomposition.
If my sampling frequency is 30kHz, then would I need to input data with 30k samples which later will ...
0
votes
1answer
30 views
Understanding index transformation in derivation of Fourier transform for sampling rate reduction
Was going over some notes regarding deriving fourier transform equation for Sampling Rate Reduction. Reference to Notes from below link https://ocw.mit.edu/courses/electrical-engineering-and-computer-...
1
vote
1answer
39 views
Oversampling a signal
I’ve built a circuit with an analogue sensor (70 Hz bandwidth) connected to a 24 bit ADC, which is oversampling the signal at 10 kHz. Nyquist sampling theorem implies I should sample by at least 140 ...
1
vote
2answers
29 views
How mic setting will affect audio classification model?
I have audio samples with three classes :
100 audio samples : class 'A'
100 audio samples : class 'B'
100 audio samples : class 'C'
...
0
votes
1answer
36 views
Downsampling - how many extra samples to include
I want to downsample a finite section of an equidistant time-series
$$x_i, \qquad i=0\dots n-1$$
by doing an FFT and dropping the upper part of the spectrum. Since the FFT looks at $x_i$ as a cyclic ...
0
votes
3answers
41 views
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 ...
0
votes
2answers
40 views
Relationship between sampling and number of pixels?
In case of digital images, what is the relationship between sampling and number of pixels? For upsampling, the number of pixels increass, and for down sampling, the number of pixels decrease??
0
votes
0answers
12 views
How do you change an instance of dsp.DigitalDownConverter object in MATLAB to work with filters other than the ones it is originally defined with?
If you look at this website:
https://www.mathworks.com/help/dsp/ref/dsp.digitaldownconverter-system-object.html
you will see an example (with code) that attempts to up convert and down convert a ...
0
votes
3answers
43 views
How and why does downsampling reduces resolution in time
in my Course we talked about filter banks and the prof said that we get reduced resolution in time because of the downsampling after the band-pass filters. Is this because we now have fewer sample ...
0
votes
2answers
52 views
Downsampling issues
I have this data that need to be downsampled so that it can be fed into a classifier. The issue is that I need to downsample from 1000Hz into 20Hz. If you see the graph below, the blue line is the ...
0
votes
1answer
36 views
How is downsampling and low-pass filtering done in MS-SSIM?
I am just studying the Multiscale Strutural Similarity measure for image quality and going through the original paper [1].
I think I understood the basic ides and "regular" structural similarity, but ...
0
votes
3answers
119 views
Can Carrier Offset cause Image Problems
The main reason why we use the Direct conversion receiver with zero IF is that we don't have to deal with the problem of images. For achieving zero IF we need to ensure that the receiver Local ...
0
votes
1answer
77 views
2D Fourier downsampling
How can one correctly downsample a Fourier 2D matrix of complex numbers ? More precisely, if I have a 2D DFT of an image:
x=phantom
X=fft2(x)
How should I do to ...
0
votes
1answer
39 views
How do wavelet levels depend on one another?
I am working with wavelets for my thesis, and I would like to know if there is an intuitive dependency between the levels of a DWT.
To make it clear: The DWT performs a convolution, and then the ...
0
votes
1answer
43 views
How should I downsample my sensor?
I have 2 sensors, sensor A is sampling a signal at 1kHz, and sensor B is sampling the a signal at 100Hz.
Every timestamp that sensor B takes a measurement at is contained in sensor A. That is, ...
-1
votes
1answer
36 views
std::cosf fluctuation: Results are off in low frequencies [closed]
I attempted to generate a continuous wave signal by using the C++ cos/sin functions. It's partly successful, meaning high frequencies seems ok, but very low frequencies give unexpected results. The ...
0
votes
0answers
33 views
Pandas resample.mean()
I have a question to all you filter experts out there. I have some engine data sampling irregularly at about 50Hz. Recently I've been downsampling via the Pandas resample().mean() method. Basically ...
0
votes
1answer
76 views
Decimation with IIR filter altering amplitude of signal
I'm downsampling a signal through decimate (scipy implementation), but the result has a different amplitude than the original signal, which if I understood correctly, shouldn't happen. The original ...
1
vote
1answer
62 views
Confused about filter's cutoff frequency in rational sampling rate converter
A interpolator which increase sampling rate by L times is followed by an anti-imaging filter, the filter is said to have a cutoff frequency of Fs/2L. Is Fs here is the frequency before or after ...
0
votes
1answer
69 views
ADC sampling rate implications Matlab/Simulink M-PSK modulation
I am trying to find a way to evaluate what would be the minimum sampling rate used in a modulated waveform using matlab / Simulink.
The real scenario would be let say a M-PSK waveform of Y bandwidth ...
0
votes
0answers
65 views
How to improve interpolation for chroma upsampling (4:2:0 to 4:4:4)?
I am trying to perform the best possible interpolation in order to perform proper chroma upsampling from 4:2:0 YCbCr to 4:4:4 YCbCr. I have implemented the improved interpolation proposed at this ...
2
votes
2answers
98 views
What is the right way to downsample using Fourier method?
I want to know what is the right way to downsample a sampled signal using Fourier transform as the implementation in scipy.signal.resample confuses me.
Reading ...
1
vote
2answers
326 views
What is the impulse response used in an interpolation filter when upsampling?
I need to downsample a single period waveform from $M$ samples to $L$ samples. If that matters, in my particular case, $L=M-1$.
I read about downsampling and came to the conclusion I need:
expand ...
0
votes
0answers
55 views
Nyquist sampling theorem / Nyquist - Shannon theorem evaluation over M-PSK
I am trying to simulate an M-PSK Tx-Rx System on Simulink and analyse what the effect of sampling rate reduction would have on it. More, particular I am trying to prove what Nyquist sampling theorem ...
2
votes
4answers
179 views
How to Downsample The Chrominance Components
So I am doing an image compression project for college and am trying to create a visual demonstration of how downsampling chrominance components can reduce the amount of digital information while ...
1
vote
3answers
2k views
downsample signal to a specific number of samples in Python
The Python Scipy library provides several functions to downsample signals, but they all have limitations:
The resample function is based on Fourier method, which means it assumes periodic signals.
...
4
votes
2answers
445 views
Downsample: resample vs antialias fitlering + decimation
I have a discrete signal sampled @Fs. I need to downsample it to Fs/k. Main reason is to reduce signal bandwidth and speed up computation : I'm only interested in a reduced bandwidth < Fs/2k. Some ...
1
vote
1answer
62 views
Improving spectral response with lost downsampled data
I have a project that is resource constrained and must maintain a specific FFT length and small FFT bin width, down at baseband. My sampling rate is very high and needs to be downsampled to anywhere ...
0
votes
0answers
37 views
How to downsample my data readings from 0.5hz to 0.001667hz. Do I filter and downsample?
I have a device that, in the lab, takes voltage readings every 2 seconds. However in real-life application the device would only wake every 10 minutes and then take a 100 readings whilst awake. How do ...
0
votes
1answer
24 views
Clarification regarding discrete wavelet transform
One of the books on "Conceptual Wavelets" by Fugal explains some major differences between the undecimated discrete wavelet transform (UDWT) vs. discrete wavelet transform (DWT). In UDWT the scale of ...
0
votes
0answers
70 views
Analog-to-Information Converters?
In Analog-to-Digital Converters(ADC), the signal is first sampled at a rate higher than or equal to the Nyquist, then quantized and encoded. In Analog-to-Informations (AIC), the sampling and ...
2
votes
1answer
111 views
FFT of white noise with different sampling rate
I have a question on how I should interpret the white noise power level (noise floor) obtain from FFT for different hardware sampling rates. I realized if I sample the same noise at different rates (...
1
vote
0answers
22 views
Bandpass Experiment: Weird graph! amplitude mismatch?
Why is this generic BP filter seem to magnifying amplitudes when I run it at lower sample rates? The bass range seems to 32 times louder at 1275 Hz (44.1 kHz / 32) than at 44.1kHz?
Here is a graph of ...
1
vote
0answers
97 views
RSP1A sample rate vs if bandwidth
I'm using the RSP1A SDR and I want to understand how to choose the best configuration for receiving a signal of 125 khz bandwidth.
I would like to know if when choosing the option 200 KHz IF ...
0
votes
1answer
231 views
How to prevent distortion after down-sampling?
I am new to audio signal processing, but in one of my machine learning projects that I am working on, I need to down-sample my audio somewhere in the middle of my neural network. Therefore, I need a ...
0
votes
1answer
124 views
Better understanding of downsampling (decimation) and upsampling (interpolation)
Although some questions were asked about this topic, I have not seen any that answers all the basic questions, that is why I took the liberty to ask more about this.
I suggest to limit, (or at lest ...
0
votes
1answer
34 views
Polyphase components Spectrum formula in Discrete time
I am trying to understand the meaning behind some of the components of the formula for polyphase components in discrete time. Note that $\Omega$ indicates discrete in this notation and the formula is ...
0
votes
1answer
56 views
How to sketch this multirate system spectrum?
In the following system:
The signal x(n) is upsampled by 2 and then filtered. The signal and the filter have the following spectrum:
After upsampling the spectrum of X would look the same except ...
1
vote
2answers
104 views
Image downsampling with Haar DWT?
How can the resolution of an image in matlab be reduced by using 2D haar wavelet by downsampling-decimation? Is there any predefined code or tool within wavemenu? thanks in advance
