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1500 questions
8
votes
3 answers
baffled by fft phase spectrum!
A very simple MATLAB experiment:
f = 200;
fs = 1000;
t = 0: 1/fs : 1;
x = cos(2*pi*f*t);
plot(angle(fftshift(fft(x))));
And here's the output:
Now, made a minor change to the above code snippet; reducing the time duration by just 1 sample,…
user4673
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8
votes
4 answers
What are Chunks when recording a voice signal
I am having trouble understanding the example program for audio recording ,
it comes with PyAudio module.
I am using an external Audio Card to record the sound , obviously, the voice should be converted into the digital form to be presented to the…
Sufiyan Ghori
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8
votes
3 answers
Object detection versus object recognition
I have a slight confusion differentiating between object recognition and object detection. Some people say object detection is a sub-topic of object recognition? Can someone clarify the the difference between these two topics?
To the best of my…
user2867655
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8
votes
4 answers
How to determine the "variability" in a frequency range?
This is a continuation of a previous question.
I'm trying to analyze breathing and snoring sounds, and while I can fairly well detect snoring now, breathing is a bigger challenge.
I've learned that if I break the analyzed frequency range (about…
Daniel R Hicks
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8
votes
1 answer
Prerequisites for audio signal processing
I started a DSP course online and quickly discovered that as much as some people say that it is possible to avoid the more advanced mathematics of signal processing, this didn't seem the case.
It seems like a solid understanding of Calculus and…
some_id
- 679
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8
votes
2 answers
Calculating the SNR of a blurred image
I have a blurred and noisy image $X$, I want to apply the Wiener filter on it and get a deblurred and denoised image $Y$ (i.e apply inverse of blurring filter while at the same time reducing some noise, if not accentuating it). I'd like to measure…
meta_warrior
- 617
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8
votes
4 answers
Preprocessing to improve Harris corner tracking between video frames?
In our unmanned aerial vehicle grayscale video image stabilization application, we're having difficulty finding the "good" Harris corners in frame N+1 selected from frame N. The source of the difficulty appears to be radical nonuniform pixel…
David Pointer
- 183
- 7
8
votes
3 answers
Simple, streaming, lossless image compression
Does anyone know of any image compression techniques with the following characteristics:
lossless
streaming - I want to compress on the fly, pixel-by-pixel.
low-memory overhead - I can afford to buffer a single line, but ideally not even that.
no…
Martin Thompson
- 1,432
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- 17
8
votes
1 answer
How to avoid denormalized numbers?
The same floating-point AMD X86-64 digital signal processing system mentioned in my previous question has a problem where it sometimes slows down substantially when signals attain values very near (but not exactly) zero.
The problem is that…
nibot
- 3,803
- 5
- 29
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8
votes
4 answers
Differences between Python and MATLAB filtfilt function
I'm trying to port some MATLAB code to Python and am running into some strange behaviour. I am implementing a 5th order Butterworth bandpass filter. The sampling rate is 30 Hz.
Running MATLAB R2012b, Spyder 2.2.0 with Python 2.7, SciPy 0.12.0 on…
limi44
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8
votes
2 answers
main direction in 2D map of data
It may be a very simple question. We would appreciate any comments, guide or complete solution. We prefer however incomplete solutions but novel practical ideas.
- How to find the main direction of variation i.e., main diagonal in the following…
Developer
- 1,129
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- 15
8
votes
1 answer
Why should one use windowing functions for FFT?
So I just revised my pitch calculation algorithm using a harmonic product spectrum algorithm. I was just curious about why this explanation of Harmonic Product Spectrum states that you need to implement a Hanning Window to the data set. What would…
Skylion
- 291
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- 12
8
votes
1 answer
Realtime fixed point IIR filter implementation in C
I would like to implement a fourth order fixed point low-pass IIR filter in C (with Q15 arithmetic), and I will prepare this filter by using two stages cascaded direct form-II bi-quad filters.
I have found countless C implementations and example…
albin
- 183
- 1
- 3
8
votes
1 answer
How to compute 2D displacement vector for binary image registration?
My inputs are several binary images like:
They have globally the same content but may be unregistered as they are produced from a hand camera. What I would like to compute is the 2D displacement vector from the first image to the second. I use…
Stéphane Péchard
- 1,039
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- 23
8
votes
2 answers
Confirmation on how to calculate phase differences at every frequency point between two wideband signals?
I have a problem that I thought was going to be simple, but it has become surprisingly stubborn and I question my method...
I have used the method (described below), but I wanted to confirm that this was the right approach, and see if there was…
Spacey
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