Signal Processing Stack Exchange
Signal Processing Stack Exchange

Most Popular

more tags
1500 questions
10
votes
1 answer

Can I use FFT to interpret accelerometer gestures?

I have the need to detect two different gestures that occur when looking at accelerometer data. Here's a run down (as brief as I can make it): Lets say an iPhone is being oscillated back and forth while remaining face-up. The user can either do one…
rykardo
  • 101
  • 1
  • 5
10
votes
2 answers

interpret wavelet scalogram

My knowledge of wavelets is less than epsilon. Bear with me. If I have a signal of two well separated sinusoids (15 and 48 Hz) plus some random noise, I can clearly make out the two in a spectrogram (the two stripes in my picture); t=0:0.002:1; %…
user1641496
  • 405
  • 1
  • 5
  • 11
10
votes
1 answer

Matlab plot of QPSK system doesn't agree perfectly with theoretical BER curves

Does anyone know if there is a simple explanation on the fact that the theoretical bit-error rate (BER) curves of a Quadrature phase-shift keying (QPSK) system are approximately 1 dB shifted from the simulated curves?
George
10
votes
3 answers

Is there a way to obtain the impulse response of a discrete system by just knowing it's response to the discrete unit step function?

In continuous time it was possible; $$ u(t){\longrightarrow} \boxed{\quad\textrm{system}\quad} {\longrightarrow} y(t)\implies \delta(t)=\frac{du(t)}{dt}{\longrightarrow}\boxed{\quad\textrm{system}\quad}{\longrightarrow} \frac{dy(t)}{dt}=h(t) $$ Does…
pyler
  • 347
  • 1
  • 2
  • 8
10
votes
3 answers

Why normalize the data set before applying Direct Linear Transform

Direct Linear Transform (DLT for short) is a method of homography estimation, it solves the overdetermined linear system via SVD $$Ah=b$$to find a solution $h$ under constraint $\|h\|=1$. Actually it finds the least square solution which minimize…
avocado
  • 877
  • 3
  • 12
  • 22
10
votes
5 answers

How can I vectorize the computations for a first-order recursive filter?

I have a simple single pole low pass filter (for parameter smoothing) that can be explained by the following formula: $$ y[n] = (1-a) y[n-1] + a x[n] $$ The architecture that I'm using has access to single-instruction, multiple-data (SIMD)…
user1132968
  • 121
  • 1
  • 5
10
votes
2 answers

Estimate Taylor series coefficients from samples of a function

Say I have measurements of a function $y = y(x)$, sampled at $x_i$ with some noise, that could be approximated by a Taylor series expansion. Is there an accepted way of estimating the coefficients for that expansion from my measurements? I could fit…
Matt
  • 913
  • 1
  • 8
  • 9
10
votes
2 answers

How to design a continuously time-variant digital filter?

I have discrete time series containing signal with smoothly varied frequency over time (called a "sweep"). How can I design a discrete filter (low-pass or band-pass in my case) of a finite length with linearly varying cut-frequency over time and…
mbaitoff
  • 307
  • 1
  • 12
10
votes
2 answers

Image Processing - Counting nuclei

I am trying to create a program that can count the number of nuclei in such an image: What I've already done is the following, step by step: Apply an Alternating Sequential Filter (closing and opening the image with gradually bigger structuring…
Thiago
  • 285
  • 1
  • 6
10
votes
3 answers

Converting mel spectrogram to spectrogram

I have a set of songs for which I extracted the STFT (Short-Time Fourier Transform) and used the magnitude spectrum $|S|$ to calculate the mel spectrogram by using a mel filterbank matrix $M$, so $X=\log(M\times |S|)$. I want to know is there any…
user76170
  • 441
  • 1
  • 4
  • 7
10
votes
3 answers

How important is it to use power of 2 when using FFT?

Here is the problem. I have a 2D array of data, first column represents the time data and the second column represents the sinusoidal response data, based on the time data. I apply fft and I get my frequency (that I started with) in a specific bin…
lamia
  • 103
  • 1
  • 1
  • 4
10
votes
2 answers

Magnitude-squared Coherence calculation inconsistence

I have to calculate the magnitude-squared coherence (MSC) between two signal. However, using a routine that uses only one taper (or no tapers at all) my result is always 1, despite the signals are clearly different. This doesn't happen if I use more…
Tojur
  • 113
  • 1
  • 6
9
votes
1 answer

How to estimate the signal-to-noise ratio of a waveform?

I have a signal: $f_i(t_i=i\Delta t)$, where $i = 0\ldots n-1$. The signal seems to vary quickly around a slower varying "trend". I am assuming that the quickly varying part is noise and the slowly varying part is the real signal. How do I estimate…
Andy
  • 1,783
  • 2
  • 17
  • 27
9
votes
2 answers

The Parameter Devil — How to set them when no validation against groundtruth is possible

Question: I want to kick up a discussion on how people set algorithmic parameters when no validation against groundtruth is possible (maybe because groundtruth just cannot be obtained or is very hard/tedious to obtain). I have read numerous papers…
cdeepakroy
  • 191
  • 3
9
votes
1 answer

Calculating smoothed derivative of a signal by using difference with larger step=convolving with rectangular window

I have a signal sampled at $\Delta t: fi(ti=i\Delta t)$ where i = 0..n-1. I want to find the first derivative of the signal: f'(t). My first thought was to estimate this by a central difference: $f'(t_i) =\frac{f(t_{i+1})−f(t_{i−1})}{2\Delta…
Andy
  • 1,783
  • 2
  • 17
  • 27
1 2 3
…
99 100