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1500 questions
22
votes
1 answer
How to Extract High Frequency and Low Frequency Component Using Bilateral Filter?
What does High frequency and low frequency component signify in an image.
How to separate out the high frequency as well as low frequency component of an image using Bilateral filter.
Deepak kumar Jha
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22
votes
5 answers
Fast Cosine Transform via FFT
I want to implement the Fast Cosine Transform. I read on wikipedia, that there is a fast version of the DCT which is similarly computed to the FFT. I tried to read the cited Makhoul* paper, for the FTPACK and FFTW implementations that are also used…
Framester
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22
votes
2 answers
Inverse Short Time Fourier Transform algorithm described in words
I'm trying to conceptually understand what is happening when the forward and inverse Short Time Fourier Transforms (STFT) are applied to a discrete time-domain signal. I've found the classic paper by Allen and Rabiner (1977), as well as a Wikipedia…
Nicholas Kinar
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22
votes
3 answers
How did they color old black and white movies?
This question is on dsp.SE as I'm mostly interested in the signal processing part.
There is an Indian movie Mughal-e-Azam which was released in 1960 in black & white which has been reproduced in color in 2004.
How did they color each pixel…
Sufiyan Ghori
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22
votes
2 answers
Power spectral density vs. FFT bin magnitude
What's the difference between these? Both are measurements of some form of signal power, but surely there's some difference between the power they are measuring?
mavavilj
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22
votes
2 answers
What's the difference between the Gabor and Morlet wavelets?
The Gabor wavelet is a kind of the Gaussian modulated sinusoidal wave (source)
Gabor wavelets are formed from two components, a complex sinusoidal carrier and a Gaussian envelope. (source)
and
In fact, the wavelet shown in Figure 2a…
endolith
- 15,759
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22
votes
4 answers
Fast / Efficient Way to Decompose a Separable integer 2D Filter Coefficients without the SVD
I would like to be able to quickly determine whether a given 2D kernel of integer coefficients is separable into two 1D kernels with integer coefficients. E.g.
2 3 2
4 6 4
2 3 2
is separable into
2 3 2
and
1
2
1
The actual…
Paul R
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22
votes
4 answers
How to distinguish voice from snoring?
Background: I'm working on an iPhone application (alluded to in several other posts) that "listens to" snoring/breathing while one is asleep and determines if there are signs of sleep apnea (as a pre-screen for "sleep lab" testing). The…
Daniel R Hicks
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22
votes
5 answers
What are the audio equivalents of images like "Lena", "Mandrill", and "Cameraman"?
I don't know what to call these images, but they're very often used in the image processing world as standard examples to show the output of a particular operation. Here's a link to the page describing Lena as a "standard test image". Are there…
aardvarkk
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22
votes
3 answers
What is the Gabor filter? And what are its main uses?
I'm doing research on the Gabor filter. When I Googled it, I found very long and complicated articles. Can anyone help me to find a simple explanation about it, or recommend a website or article to read?
I want to understand this filter in order to…
toto
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22
votes
2 answers
Improving spectrogram resolution in Python?
I'm using the specgram() function in matplotlib to generate spectrograms of speech wave files in Python, but the output is always of vastly inferior quality to what my normal transcription software, Praat, can generate. For example, the following…
Alek Storm
- 323
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22
votes
1 answer
Difference Between Correlation and Convolution in the Context of Image Processing
Could you please clearly explain what is the difference between correlation and convolution that is done by a filter on an image?
I mean in terms of signal processing definition I know that convolution describes the output of an LTI system, that is…
the_naive
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22
votes
2 answers
Examples of Independent and uncorrelated data in real-life, and ways to measure/detect them
We always hear about this vector of data VS this other vector of data being independent from each other, or uncorrelated, etc, and while it is easy to come across the math regarding those two concepts, I want to tie them into examples from…
Spacey
- 9,817
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22
votes
2 answers
Why do we use keypoint descriptors?
I just studied about SURF and I'm going for its implementation, but I still didn't understand why we use descriptors.
I understand what keypoints are and their purpose, but when we extract the keypoints than why do we need to use descriptors ? What…
ARG
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22
votes
2 answers
What is cross-spectral density- CSD?
I asked a question earlier but I didn't get any answer for it. So now I am simplifying it: what are Cross-Spectral Density (CSD) and Power-Spectral Sensity (PSD)? What is their application? How can I get them in…
SAH
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