Greatest Hits

86 votes
4 answers

What is meant by a system's "impulse response" and "frequency response?"

Can anyone state the difference between frequency response and impulse response in simple English?
Ant's's user avatar
  • 1,062
15 votes
6 answers

What Are Linear and Circular Convolution?

I have some basic understanding of signals and convolution. As far as I know it shows the similarities of two signals. Could I get some explanation in plain English of: what are the linear and ...
Sturm's user avatar
  • 336
146 votes
8 answers

Why is the Fourier transform so important?

Everyone discusses the Fourier transform when discussing signal processing. Why is it so important to signal processing and what does it tell us about the signal? Does it only apply to digital signal ...
jcolebrand's user avatar
  • 1,579
64 votes
17 answers

What is the physical meaning of the convolution of two signals?

If we convolve 2 signals we get a third signal. What does this third signal represent in relation to the input signals?
Parag's user avatar
  • 743
43 votes
5 answers

Difference between Discrete Time Fourier Transform and Discrete Fourier Transform

I have read many articles about DTFT and DFT but am not able to discern the difference between the two except for a few visible things like DTFT goes till infinity while DFT is only till $N-1$. Can ...
BaluRaman's user avatar
  • 689
10 votes
2 answers

What is the difference between Lumped and Distributed systems?

What are the salient differences between Lumped and Distributed systems? In what contexts are distributed systems the appropriate model and in what are lumped systems the appropriate model? Also, ...
Gowtham's user avatar
  • 237
119 votes
12 answers

What is the physical significance of negative frequencies?

This has been one of the holes in my cheddar cheese block of understanding DSP, so what is the physical interpretation of having a negative frequency? If you have a physical tone at some frequency ...
Spacey's user avatar
  • 9,837
101 votes
6 answers

Why should I zero-pad a signal before taking the discrete Fourier transform?

In an answer to a previous question, it was stated that one should zero-pad the input signals (add zeros to the end so that at least half of the wave is "blank") What's the reason for this?...
Jonas's user avatar
  • 3,081
8 votes
4 answers

How to check if a signal is power signal or energy signal?

What is the procedure to check the signal type? example: $ x(t) = A \sin (\omega t) $ $ y(t) = A e^ {-\lambda |t|} $
Giannis Foulidis's user avatar
12 votes
4 answers

Difference between Digital signal and Discrete signal

I have just started studying Digital Signal Processing. Can someone explain what is the difference between a Discrete Signal and a Digital Signal in simple words? Thanks in advance !
praghu's user avatar
  • 121
12 votes
2 answers

Filtering 50Hz using a notch filter in MATLAB

I've read up a lot about this, but haven't been able to piece everything together successfully, so I'm looking for some help. I need to filter 50 Hz from a signal. It looks like the best options are ...
Dororo's user avatar
  • 293
21 votes
4 answers

How to mimic/copy/fake someone's voice?

Is there any existing application to sample someone's voice and use it to modulate any other voice or synthesize a text to resemble the original one? For example, this Text-to-Speech Demo by AT&...
clapas's user avatar
  • 313
78 votes
9 answers

Why do we use the HSV colour space so often in vision and image processing?

I see the HSV colour space used all over the place: for tracking, human detection, etc... I'm wondering, why? What is it about this colour space that makes it better than using RGB?
porridge's user avatar
  • 781
15 votes
6 answers

What is the first derivative of Dirac delta function?

Could you please help me in a simple way, what is the first derivative of a Dirac delta function? I found this answer: The informal answer is a positive Delta function immediately followed by a ...
Amro Goneim's user avatar
186 votes
5 answers

"River" detection in text

Over on the TeX stackexchange, we have been discussing how to detect "rivers" in paragraphs in this question. In this context, rivers are bands of white space that result from accidental alignment ...
Lev Bishop's user avatar
  • 1,633
72 votes
8 answers

How do I implement cross-correlation to prove two audio files are similar?

I have to do cross correlation of two audio file to prove they are similar. I have taken the FFT of the two audio files and have their power spectrum values in separate arrays. How should I proceed ...
user avatar
131 votes
5 answers

What does frequency domain denote in case of images?

I was just learning about the frequency domain in images. I can understand the frequency spectrum in case of waves. It denotes what frequencies are present in a wave. If we draw the frequency ...
Abid Rahman K's user avatar
107 votes
4 answers

What is the difference between a Fourier transform and a cosine transform?

In speech recognition, the front end generally does signal processing to allow feature extraction from the audio stream. A discrete Fourier transform (DFT) is applied twice in this process. The first ...
Nate Glenn's user avatar
  • 1,187
64 votes
6 answers

What is the distinction between ergodic and stationary?

I have trouble distinguishing between these two concepts. This is my understanding so far. A stationary process is a stochastic process whose statistical properties do not change with time. For a ...
Matt's user avatar
  • 913
53 votes
6 answers

The difference between convolution and cross-correlation from a signal-analysis point of view

I am trying to understand the difference between convolution to cross-correlation. I have read an understood This answer. I also understand the picture below. But, in terms of signal processing, (a ...
MathBgu's user avatar
  • 633
55 votes
5 answers

What is the difference between phase delay and group delay?

I'm studying some DSP and I'm having trouble understanding the difference between phase delay and group delay. It seems to me that they both measure the delay time of sinusoids passed through a ...
dB''s user avatar
  • 1,045
26 votes
6 answers

What is a frequency bin?

I'm doing a research on the FFT method, and a term that always comes up is "frequency bin". From what I understand, this has something to do with the band created around the frequency of a given ...
JonTrav1's user avatar
  • 261
50 votes
3 answers

Why is the FFT "mirrored"?

If you do an FFT plot of a simple signal, like: t = 0:0.01:1 ; N = max(size(t)); x = 1 + sin( 2*pi*t ) ; y = abs( fft( x ) ) ; stem( N*t, y ) 1Hz sinusoid + DC ...
bobobobo's user avatar
  • 945
20 votes
3 answers

What is the difference between linear and non-linear filters?

How a mean filter is called as linear filter and a median filter is called as non linear filter? I understand how a mean and median filter operates, but I was not able to relate with the term linear ...
preethi's user avatar
  • 923
60 votes
10 answers

Meaning of Hilbert Transform

I understand the Fourier Transform which is a mathematical operation that lets you see the frequency content of a given signal. But now, in my comm. course, the professor introduced the Hilbert ...
MathieuL's user avatar
  • 765
11 votes
3 answers

Apply Low pass Butterworth filter in Python

I want to use a low pass Butterworth filter on my data but on applying the filter I don't get the intended signal. Here is the dummy code: Signal A: ...
Haroon Lone's user avatar
34 votes
2 answers

What is the cut-off frequency of a moving average filter?

I need to design a moving average filter that has a cut-off frequency of 7.8 Hz. I have used moving average filters before, but as far as I'm aware, the only parameter that can be fed in is the number ...
CaptainProg's user avatar
14 votes
2 answers

how do I calculate SNR of noisy signal?

I am having problems in understanding how to do it practically I have a wav file that contains pure speech and another ave file that just contains the background noise (can be various things, such as ...
user13267's user avatar
  • 533
29 votes
4 answers

Gaussian Blur - Standard Deviation, Radius and Kernel Size

I've implemented a gaussian blur fragment shader in GLSL. I understand the main concepts behind all of it: convolution, separation of x and y using linearity, multiple passes to increase radius... I ...
LodeRunner's user avatar
11 votes
3 answers

What is the Fourier Transform of a constant signal?

I am trying to figure out what the fourier transform of a constant signal is and for some reason i am coming to the conclusion that the answer is 1. Or better yet a step function.
Micheal C.'s user avatar
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 ...
the_naive's user avatar
  • 363
31 votes
3 answers

Variance of White Gaussian Noise

It could seem an easy question and without any doubts it is but I'm trying to calculate the variance of white Gaussian noise without any result. The power spectral density (PSD) of additive white ...
Mazzy's user avatar
  • 555
8 votes
6 answers

Why Carrier signal can't have frequency less than Message signal

I know that why we use Carrier of high frequency to send message signal over a long distance, when the frequency is low , energy will be obviously low. To increase the energy of the signal we need to ...
Sufiyan Ghori's user avatar
11 votes
4 answers

Peak Signal to Noise Ratio (PSNR) in Python for an Image

How do I calculate the maximum signal to noise ratio (PSNR) in Python? Is there any library that can calculate PSNR for Image?
Sudip Das's user avatar
  • 211
65 votes
6 answers

If humans can only hear up to 20 kHz frequency sound, why is music audio sampled at 44.1 kHz?

I read in some places that music is mostly sampled at 44.1 kHz whereas we can only hear up to 20 kHz. Why is it?
Soham De's user avatar
  • 752
38 votes
7 answers

Understanding the Matched Filter

I have a question about matched filtering. Does the matched filter maximise the SNR at the moment of decision only? As far as I understand, if you put, say, NRZ through a matched filter, the SNR ...
user968243's user avatar
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's user avatar
  • 1,414
7 votes
2 answers

Relation between Laplace and Fourier transforms

I know that $$X_L(s) \Big|_{s=j\omega}=X_F(\omega)$$ if $x(t)$ is one sided and absolutely integrable and hence the imaginary axis of the Laplace transform is the Fourier transform. But Fourier ...
Vlad's user avatar
  • 225
8 votes
7 answers

How to implement a moving average in C without a buffer?

Is it possible to implement a moving average in C without the need for a window of samples? I've found that I can optimize a bit, by choosing a window size that's a power of two to allow for bit-...
tarabyte's user avatar
  • 395
21 votes
3 answers

FIR filter with linear phase, 4 types

I know there are 4 types of FIR filters with linear phase, i.e. constant group delay: (M = length of impulse response) Impulse response symmetrical, M = odd Imp. resp. symmetrical, M = even Imp. resp....
Vidak's user avatar
  • 595
35 votes
6 answers

Why is a linear phase important?

If symmetry conditions are met, FIR filters have a linear phase. This is not true for IIR filters. However, for what applications is it bad to apply filters that do not have this property and what ...
The Pheromone Kid's user avatar
33 votes
4 answers

How to understand Kalman gain intuitively?

The Kalman filter algorithm works as follows Initialize $ \hat{\textbf{x}}_{0|0}$ and $\textbf{P}_{0|0}$. At each iteration $k=1,\dots,n$ Predict Predicted (a priori) state estimate ...
Tim's user avatar
  • 611
10 votes
3 answers

the relationship between bandwidth and the datarate

One Question of my note is like this. ...
Samuel's user avatar
  • 415
77 votes
4 answers

What are some free alternatives to SIFT/ SURF that can be used in commercial applications?

As far as I understand, both SURF and SIFT are patent protected. Are there any alternative methods that can be used in a commercial application freely? For more info on the patent check out: http://...
Andrey Rubshtein's user avatar
38 votes
5 answers

Why are Gaussian filters used as low pass filters in image processing?

In 1d signal processing, many types of low pass filters are used. Gaussian filters are almost never used, though. Why are they so popular in image processing applications? Are these filters a result ...
nimrodm's user avatar
  • 886
31 votes
1 answer

Kalman filter for position and velocity: introducing speed estimates

Thanks to everyone who posted comments/answers to my query yesterday (Implementing a Kalman filter for position, velocity, acceleration ). I've been looking at what was recommended, and in particular ...
Stochastically's user avatar
2 votes
2 answers

How to apply Hamming Window?

I am new in matlab and signal processing. The time series that have been used are obtained from accelerometer in a building. As far as I understand both the time series' length and window function ...
sedef's user avatar
  • 21
16 votes
1 answer

Converting frequency from $\textrm{Hz}$ to radians-per-sample

In MATLAB I have to pass cut-off frequency for designing a filter. But this Cut-off frequency is in radians-per-sample. How do I convert my analog Cut off frequency in $\textrm{Hz}$, into the required ...
gpuguy's user avatar
  • 1,370
37 votes
2 answers

Filter order vs number of taps vs number of coefficients

I'm learning DSP slowly and trying to wrap my head around some terminology: Question 1: Suppose I have the following filter difference equation: $$y[n] = 2 x[n] + 4 x[n-2] + 6 x[n-3] + 8 x[n-4]$$ ...
stackoverflowuser2010's user avatar
21 votes
3 answers

OpenCV/C++ connect nearby contours based on distance between them

I have to connect nearby contours in an image based on the distance between them which specifies if the contours are to be connected. Now there's a question already on the same problem here https://...
Roney Island's user avatar