Unanswered Questions
5,021 questions with no upvoted or accepted answers
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
3answers
19k 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:
$$
\frac{Y(s)}{U(s)}= \frac{\omega_{c}}...
9
votes
0answers
1k views
Help in Retraining a HOG Descriptor using SVMLight
I am currently trying to count cars using OpenCV 2.4.4 with a HOG descriptor. Because a model for car detection is not available in OpenCV, I am creating my own model using SVMLight and a dataset of ...
7
votes
0answers
119 views
Converting very short "motionless" video frames to single, better-resolved, images
I made a mistake with my newly bought compact camera, before a trip to Japan. Instead of taking single pictures, I ended up with a few short "MP4" video files (1 second, 2-3 frames). I could ...
7
votes
3answers
558 views
Efficient calculation of correlation function every $N^{\rm th}$ point
I would like to calculate a long correlation function of length say, 1e6 points.
I have a prior knowledge that the correlation peak will be in point k*1000.
Is there an efficient way to apply this ...
6
votes
2answers
208 views
Filter design to realize Cauchy product
I come from Computer Science so please pardon for my possibly wrong terminology.
I need to design a filter which has coefficients
$$h_0, h_1, \ldots, h_n, \ldots \quad\text{such that}\quad h_0 > ...
6
votes
1answer
333 views
Detect quasi-parallel lines with spurs in a binary image
I'm looking for a way to remove quasi-parallel curves from the net, as depicted in the figure. Not only the original nets (upper row in figure) contain many spurs, but also the curves to be detected ...
6
votes
1answer
323 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
0answers
2k views
Jacobian Matrix of a Quaternion $q$ respect to Angular Velocity $\omega$
In the context of visual tracking and video processing I need to estimate variations of the orientation related to the angular velocity. I am trying to calculate the Jacobian matrix of a quaternion $\...
6
votes
0answers
180 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}...
6
votes
1answer
1k views
How to choose a windowing function when performing a Chirp $\mathcal Z$-transform?
I've got some data sampled at 32 Hz. The only interesting stuff is happening between about 0-8 Hz and I've got to do real time batch processing and detect events with a delay of no more than a second. ...
5
votes
0answers
82 views
Find moments of a discrete process using $\mathcal{Z}$-Transform method
For a linear process relating a variable $Y_i$ to random, independent variables $X_i$ using the equation:
\begin{equation}
Y_i = aY_{i-1} + (1-a)X_i
\end{equation}
which has the solution:
\begin{...
5
votes
0answers
85 views
Is the Wiener filter operating at the Cramér–Rao bound?
I have been told (Wikipedia agrees) that the Wiener filter is optimal when signal and (additive) noise are WSS. Optimal in the sense that it minimizes the mean-square error.
The Cramér–Rao bound is ...
5
votes
0answers
111 views
Efficient Convolution Without I/O Delay (Gardner 1995) implementation
I am trying to perform real-time convolution on an audio stream using a fairly large FIR for convolutional reverb.
I found a great paper explaining how to do just that: Gardner, 1995. But, I'm new to ...
5
votes
0answers
175 views
Residual error when setting measurement matrix in compresssive sensing
I have an issue when implementing compressive sensing to recover sparse vector. Assume I have sparse vector $x$ of length, for example, $(256,1)$. $x = [x_1,x_2,.....x_{256}]$. This vector is ...
