Unanswered Questions
4,379 questions with no upvoted or accepted answers
14
votes
2answers
502 views
When does the laugh track kick in?
One of my weekend projects has brought me into the deep waters of signal processing. As with all my code projects that require some heavy-duty math, I'm more than happy to tinker my way to a solution ...
11
votes
0answers
668 views
Will an Unscented Kalman Filter Be “As Good” as Other Optimization Algorithms for This Problem?
I want to calibrate a tri-axis magnetometer when a tri-axis gyroscope is also available.
I am fairly certain I can solve this problem using various optimisation algorithms, but I would prefer to use ...
10
votes
0answers
1k views
Ensemble learning, multiple classifier system
I am trying to use a MCS (Multi classifier system) to do some better work on limited data i.e become more accurate.
I am using K-means clustering at the moment but may choose to go with FCM (Fuzzy c-...
9
votes
0answers
1k views
Help in Retraining a HOG Descriptor using SVMLight
I am currently trying to count cars using OpenCV 2.4.4 with a HOG descriptor. Because a model for car detection is not available in OpenCV, I am creating my own model using SVMLight and a dataset of ...
9
votes
1answer
271 views
What is the normalization factor for the quincunx lattice wavelet transform, and how do you find it?
On pages 57-60 (preview was available last I checked, images here in case), there is a quincunx lattice transform described.
Lattice:
...
8
votes
3answers
13k views
First order low pass filter
I am trying to better understand the first-order low pass filter:
Summary:
Per wikipedia, a first order low pass filter yields the following in discrete time:
$$
\frac{Y(s)}{U(s)}= \frac{\omega_{c}}...
7
votes
2answers
798 views
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 ...
7
votes
0answers
250 views
What's the similarities and differences between Wigner transform and wavelet transform?
Wigner transform and continuous wavelet transform are both some kind of time-frequency representation of a signal. What are the similarities and differences between them? Could you give some ...
6
votes
0answers
82 views
Converting very short “motionless” video frames to single, better-resolved, images
I made a mistake with my newly bought compact camera, before a trip to Japan. Instead of taking single pictures, I ended up with a few short "MP4" video files (1 second, 2-3 frames). I could ...
6
votes
1answer
1k views
Issues with the smoothing operator in coherence estimation using the complex Morlet (Gabor) wavelet
The goal
I wish to compute the coherence estimate using the continuous wavelet transform (CWT) of a real-valued signal with the complex Morlet (a.k.a. Gabor) wavelet. I compute the cwt of the signal ...
6
votes
2answers
477 views
Efficient calculation of correlation function every $N^{\rm th}$ point
I would like to calculate a long correlation function of length say, 1e6 points.
I have a prior knowledge that the correlation peak will be in point k*1000.
Is there an efficient way to apply this ...
6
votes
1answer
276 views
Analytical Expression for Convolution of Two 2D DFTs
I am trying to do an image analysis problem on some images, and I want to calculate some things in the frequency domain which are giving me problems. Say I have an (discrete) image $I(x,y)$ of size $...
6
votes
2answers
3k views
Filter size vs. FFT size and Overlap add
First of all I would like to say that :
I'm new to DSP and in a "learning curve" hence the "basicness" of my questions.
I've read as many posts/articles as possible on the ...
6
votes
1answer
386 views
Deconvolution Question on Article “Deriving Intrinsic Images from Image Sequences” by Yair Weiss
there are n derivative filters: $f_i$, and denote $f_i^r$ as $f_i$'s reverse filter such that
$$f_i(x,y)=f_i^r(-x, -y)$$
$r_i, f_i$ given, to find $r$ from the equations:
$$f_i * r = r_i, (1 \leq i \...
6
votes
0answers
177 views
EWMA based differential that is strictly positive on strictly increasing irregular time series?
Let's say I have a time series $ \{t_i, x_i\} $ where the $x_i$ are strictly increasing and the $t_i$ are not regularly spaced. I can define a differential operator as
$$ \Delta_i = \frac{x_i-x_{i-1}...
