8 votes
Accepted

Suggested Preprocessing methods for OCR on Circular Images

Here is what I did for a client (What you are asking is the same). Assuming that you have access to certain type of a pattern on the image (or the center of the hole), you could always detect the ...
  • 5,255
7 votes

Should I Use a High Pass Filter (HPF) or Low Pass Filter (LPF) to Enhance the Features for Image Splicing Detection?

Since you're after a filter which emphasizes abrupt changes you should use High Pass Filter. The issue is you'd be also sensitive to noise. Hence one way to do it is to apply High Pass Filter on ...
  • 42.5k
6 votes

What Is the Best Color Space to Work with for Hand Detection: RGB, HSV, or YCrCb?

Intuitively, HSV is the place to easily define Skin Color Hues. Yet there is a broad work on that and even articles about the optimal Color Space for Skin Detection. Yet, you should have a look at ...
  • 42.5k
6 votes

Detect a Frequency Change in a Step Wise Frequency Chirp

There are many way to tackle this: Time - Frequency Analysis Classic choice would be a spectrogram but probably a Fourier Synchrosqueezed Transform would do a better job (Have a look at even more ...
  • 42.5k
5 votes

Radar signal processing flow chart

Part of your misunderstanding comes from the fact that there are many ways in which the radar signal processing chain is implemented. Depending on the type of radar, targets of interest, hardware, etc....
  • 1,841
5 votes
Accepted

Absolute value based AM envelope detection viewed in the frequency domain

$\DeclareMathOperator{\sgn}{sgn}$ The modulating signal in AM is $$s(t) = C + a(t)\text,$$ where $a(t)$ is the (audio) amplitude, and $C$ is a constant so that $s(t) \ge 0 \;\forall t$. (Otherwise, ...
5 votes

Slicing an Image into Tiles According to Content

Under the following assumptions (Written for the vertical lines, same for the horizontal): The background is uniform. There at least a gap of 2 background pixels between the closest objects on ...
  • 42.5k
4 votes

Pulse duration detection

That looks a lot like an exponentially decaying sinusoid. What you are primarily interested in is the decay rate. Where it ends would then have to be defined as when it reached some threshold level. ...
  • 6,911
3 votes

Best DSP algoritms for ultrasonic background noise cancellation

One way to do this is to look at modeling your signal: $$ x[n] = x_h[n] + x_n[n] $$ where $x_h$ is the hissing sound and $x_n$ is the noise. If you can say that $x_n$ is modeled as: $$ x_n[n] = \sum_{...
  • 23.1k
3 votes

Probability of False Alarm versus SNR

Hi: In statistics we call that the probability of type I error ( rejecting when true ) and type II error ( accepting when false ). The way it's done there is that, once you make an assumption about ...
  • 1,082
3 votes

How detect signal from noise?

I have dealt with similar problems before. Probably the first you need to know is how does the noise spectrum look like. First approach (mostly empirical): I see your signal of interest (SoI) is a ...
3 votes

CFAR Detectors and Interference

The "best" detector is a highly subjective subject, and there is (in my opinion) not a definitive answer here. I work in radar processing and I've used everything that you've mentioned in one form or ...
3 votes
Accepted

Detect low power DSSS-BPSK signal

Without disagreement to Dilip's valid comments, this is to show the corner case as to when you can detect the presence of DSSS. This is not demodulating the data but detecting the presence of a ...
  • 38.4k
3 votes
Accepted

where we use estimation and detection in communication system?

Don't worry too much about defining these terms too precisely, because they are used in many contexts with slightly different meanings. In very general terms, "estimation" is the calculation ...
  • 13.9k
2 votes
Accepted

Efficient Marker Detection for Images

This is a saddle point. I would suggest using derivative operators to spot such discontinuities. In fact, Haralick presents a broad overview of these methods in his Topographic Primal Sketch. The use ...
  • 5,255
2 votes

Note Recognition Software

This is an old question, but one that comes up often enough that I thought I'd add this resource that I just ran across: open source software (in Swift) that might be useful to others interested in ...
  • 121
2 votes

Ship detection from aerial image

I have used Laplacian of a gaussian filtered image with sigma value of 3. I have thresholded the LoG image with a high-pass filter. I have used gray closing morphologic operator. I have filtered the ...
  • 180
2 votes

Key detection Dance Music inaccuracies - matlab

A 12-dimensional chromagram may not estimate pitch very well, given synthesized semi-tonal sounds that include lots of energy at multiple odd harmonics, as those harmonics will often end up in the ...
  • 34.1k
2 votes

how to detect short pause in a speech with noise?

You can use Voice Activity Detector(VAD) for detecting the pauses in speech and there location(and duration). if your input signal is not very noisy and noise is not varying much you can use a fixed ...
2 votes

Are radar resolution and detection capabilities not very tightly related?

I'll provide a slightly different perspective. Detection is usually measured against the noise and/or clutter statistics, so you end up with a detection probability which is a function of Signal to ...
  • 2,761
2 votes

Are radar resolution and detection capabilities not very tightly related?

If you can detect the target separately , you have resolved the targets. If you resolved two targets, you have detected them too. In general you are totally right, radar can detect targets and in ...
  • 388
2 votes

Are radar resolution and detection capabilities not very tightly related?

Resolution is (usually) referred to as the ability to distinguish two closely separated returns, not targets. The distinction is how far along the processing chain of the radar you are, resolution, ...
  • 185
2 votes
Accepted

Face Recognition: Simplistic Explanation on PCA Eigenface Algorithm

The step-to-step explanation in Eigenface seems quite clear to me. A covariance matrix is like an high-dimensional extension of the variance, which is computed by removing the average from your only ...
2 votes

How to determine the symbol rate of a 2-FSK signal?

One approach could be to perform an FM-detection step (e.g. an atan2() operation followed by a first-order difference) to transform the waveform to measurements of ...
  • 23.8k
2 votes

How does the PASCAL VOC challenge evaluate the task of object detection?

The detection task is: Given an image $I$, does it contain a sub-image $S$ (or an object $S$)? There are several things that can happen: $I$ contains $S$ and the detector says $I$ contains $S$ This ...
  • 23.1k
2 votes

How to reliably detect the state (opened or closed) of sliding doors from a statically-positioned video stream

To better deal with occlusions, my idea would be to separate this problem into detecting if: the 1st door is in position fully opened (1) the 1st door is in position fully closed (2) the 2nd door is ...
2 votes

If I line in the sound from a video game console, can I detect when a sound is played?

Theoretically you could separate your desired sound by ICA method or other blind source separation methods from the background music, then design a matched filter by your separated sound. The matched ...
  • 1,306
2 votes
Accepted

AWGN continous time channel + colored noise

To solve this problem, it is necessary to understand what exactly is meant by $\langle R, \psi_1 \rangle$ and $\langle R, \psi_2 \rangle$. These are the outputs of correlators or matched filters and ...
2 votes

Interpolating Filter for Quadrature Detector with one ADC

Q1: Which Matlab calculation is right The interpolation filter is done after the zero stuffing as that process of inserting zeros creates images in the resulting spectrum, so this filter would be at ...
  • 38.4k

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