In signal processing, downsampling (or "subsampling") is the process of reducing the sampling rate of a signal.
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Oversampling then filtering and downsampling
Currently I'm working on a project to record ELF (Extremely Low Frequency) signals from a receiver. The highest frequency of interest is about 30 Hz and the system should have a flat frequency ...
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1answer
80 views
Downsampling and Gradient filtering
Are the following sequence of operations the same -
Down-sampling filtering followed by gradient filtering with kernel [-1 0 1]
Gradient filtering with kernel [-1 0 1] followed by down-sampling
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4answers
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How can I resample a signal with an arbitrary factor (e.g. 128000Hz to 16000.1Hz) in Matlab?
I need to simulate the sampling of a continuous (fsCtu = 128000Hz), acoustic signal with two microphones that have a slight offset in sampling rate (fsMic1 = 16000, fsMic2 = 16000.1) in Matlab. What ...
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Sample keypoint found in multi-scale to one scale (scale space with O octaves)
For a multi-scale keypoints detector, local extremas are found between the scales at EACH octave.
The scale-space is implemented as follows:
Each octave is downsampled by half from the first image in ...
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3answers
1k views
Practical Applications of upsampling and downsampling
I'm a complete novice to digital signal processing, and I've started reading a few books on it. In particular, I've run across the concept of upsampling and downsampling. As I understand it, given a ...
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Z-transform of a downsampler
In this paper or multirate filtering, the author establishes the following mathematical relationship. Let $y_D$ be the output of a downsampler such that
$$y_D[n] = x[Mn]$$
where $M$ is the ...
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2answers
244 views
Downsample Equiripple FIR filter
I am designing some Downsampling filters using the remez exchange algorithm (Matlab FDAtool). I see that some times i get a spike at the first and last coefficients. does anybody knows why is that? my ...
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1answer
212 views
Converting from stereo to mono by averaging
Hi I'm doing a past exam question about converting from stereo to mono. The scenario is below:
The first question is: Explain why would this result in a noisy encoding. How is the noise ...
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1answer
179 views
Reference for Supersampling
I want to downsample images to arbitrary sizes using supersampling to avoid aliasing effect.
The only two good explanations I found were on Wikipedia and everything2.com, but there are still gaps. ...
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2answers
832 views
How to extract vocal part from stereo audio signal?
I'm now processing MP3 file and encounter this problem. My MP3 is stereo encoded. What I want to do is extract vocal part for further processing(whatever mode of output signals, mono or stereo are ...
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2answers
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Downsampling lowpass filter for audio: FIR or IIR?
I'm working on a real-time audio processing project in which I have to downsample a 44.1 kHz to a yet-to-be-determined lower sampling rate essentially for reducing computational complexity. I'm ...
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3answers
704 views
What is anti-alias pre-filter for preventing aliasing after under-sampling?
We know that the under-sampling results in aliasing and frequencies higher than half of the Nyquist rate is not distinguishable. I've a base band signal that I want to use the higher frequencies which ...
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3answers
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What is the effect of aliasing on the magnitude of the autocorrelation?
I've a question about the effect of aliasing on the magnitude of autocorrelations. From a simulation in MATLAB, I don't see any effect of aliasing or any need to anti-alias filter when I take the ...
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538 views
Why would I leave a signal oversampled?
I can't think of a better way for asking this question so I will start with an example. Suppose that I have an input signal with a max frequency of 50Hz (sampled at 100Hz). Now the signals of interest ...
