In signal processing, a filter is a device or process that transforms a signal by selectively choosing specific frequencies and leaving others with appropriate gain or as it is.

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What is the cause of slow roll off of windowed filters

Exactly why using the of windowing function, such as Hamming or Blackman, causes a slower transition to stop band? Everywhere it is mentioned just as an obvious fact that this happens but I haven't ...
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18 views

Filter signal1 from evolving frequency response of signal2

I'm a composer (of music) starting out with signal processing. I'm also reasonably proficient in C at this point. I'm not even sure if what I'm trying to do is possible, because I can't yet find an ...
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2answers
30 views

Median filter algorithm in opencv

I was wondering about the implementation of the Median Filter in opencv because I am suffering form its slowness. So, I intend to implement another one on my own but first I want to make sure about ...
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47 views

FIR filter coefficients from frequency responses

I have frequency responses of FIR filter of order 13 from obtained 50 frequency samples. How can I get FIR filter coefficients of order 13? For example, in MATLAB a lot of possible ways I tried ; I ...
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4answers
60 views

Noise Removal from an image using Opencv

I tried removing noise from the image shown below using Median Blur in OpenCV. But i'm not able to remove the colour noise completely as it is done in Neat Image. Any suggestions.? 1. Original Input ...
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7 views

Determining if an unknown signal has “converged” or become quasi-steady

Relevant background: I am trying to simulate unsteady flow in a converging-diverging nozzle, and trying to see how the flow shedding downstream of the nozzle affects the wall shear stress ...
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24 views

system identification with delayed desired signal

I have a white noise data for 10 sec ( with 2 min silence or zero data at start and end)that is captured by sensor after delay t1( which I dont know). same data is captured after delay t1 and t2 by ...
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2answers
46 views

Wiener filter optimal coefficients and the input signal

I have this question: "Show that for the optimal filter coefficients the error $e[n]$ is orthogonal to the input signal $w[n]$." anybody have an idea?
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52 views

How can I Enhance this license plate images to binarize - image processing LPR

I have some License Plate images, I want to Binarize this plates to read by OCR, How can I Enhance this plates to improve results of my binaraization? some of my results: ...
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59 views

Applying Gaussian Blur in frequency domain

Please see second update I'm trying to implement gaussian blur in frequency domain using c#. Those are steps that I'm doing: Load bitmap. Split bitmap into separate color channels. Convert every ...
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1answer
31 views

Filter wrap-around to avoid dealing with settling time? Using a Butterworth

I've been using a Butterworth high pass filter to correct the low frequency distortion of an acceleration waveform integrated to a velocity waveform. I throw out a small number of the first data ...
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1answer
64 views

Spectral leakage issue cannot solved using windowing

I am designing a frequency lowpass filter using FFT&IFFT. My test data is a time series with a large DC component (the pink curve). Before the FFT, the time series was detrended (curve fitting) to ...
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2answers
42 views

Melody/Vocal extraction

I'm new to the whole DSP area, but I've built a program which plays music and does FFT to produce some cool visuals for the music in realtime. The FFT algorithm I chose was from a C# library called ...
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9 views

implementing bandwidth filter in R

I am reading this "how to" in R: http://www.inside-r.org/howto/time-series-analysis-and-order-prediction-r I am confused about the tutorial's implemented band pass filter. In particular, here's the ...
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2answers
85 views

Are SOS structures better for linear phase FIR filters?

I've seen many discussions suggesting that SOS's are often/usually the preferred structure for fixed point hardware filter implementations, since they preserve conjugate pairs, etc., but I've never ...
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1answer
29 views

transfer function of wiener filter

I am trying to understand the function of a Wiener filter. I get that the Wiener filter minimizes the mean square error between the estimated random process and the desired process. Does this mean ...
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0answers
15 views

Wavelets and filters?

I've tried using the search function to answer this question, but haven't found any explicit answers. I'm trying to study Gabor and log-Gabor filters. Most of the content I find is on Gabor wavelets ...
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1answer
46 views

How to account for sample rate in a FIR Digital Filter?

As a learning exercise I am trying to simulate a simple notch filter with Matlab. For test purposes I use Matlab to simulate sinewaves of various frequencies and plot frequency vs. gain so I can see ...
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22 views

scaling issue when using scypy's firwin2 to get coefficients for a filter

I am trying to use SciPy's firwin2 command to get the coefficients that correspond to a filter of my creating. I took white noise in Audacity, applied an ...
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26 views

Tradeoff between Filter Order and Sections

I have designed a bandpass IIR butterworth filter with desired response using the MATLAB FDAtool with the configuration shown in the figure below Since this is multistage implementation, when I ...
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2answers
39 views

what is the theory behind matlab butter function?

I would like to know the theory behind matlab butter function. Is there any book which gives clear idea on how it works. In future I would like to calculate the coefficients manually.
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5 views

Gabor filter bank for gist features

I was reading a paper about Gist features. I was interested about its code implementation which i found it here). Into LMgist.m there is a function called createGabor, this is the code: ...
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1answer
38 views

1D filter for speed input and noisy position sensor

I was tasked with designing a filter to smooth out a translating table. The system, we command a speed and a desired position, and measure it with two noisy position sensors. The commanded speed is ...
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58 views

Basic “filtering” in digital communications

I am completely stuck on solving some problems for my digital communications class. Junior level undergrad class, so fairly basic. I have been searching around all day for related articles etc but ...
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23 views

FFmpeg audio filter pipeline for speech enhancement

Using ffmpeg, I'm recording a talk, its audio with a semi-distant microphone. It makes sense to somewhat enhance the speech clarity, reduce background static and ...
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1answer
72 views

What is the advantage of weighted median filter over median filter?

I could not find any proof or comparison of weighted median and median filters.Yes the more occuring pixel contributes much but what should be the criteria of choosing weight function.And any ...
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27 views

Sparse Signal Dense Noise

If I have a sparse signal contaminated with dense noise, and if I don't have a reference signal to help me, what techniques are suitable to recover the signal? I don't know what the original signal ...
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1answer
58 views

Calculating FIR filter coefficients with the windowing method and Convolution algorithm [closed]

Please advice how to calculate FIR filter coefficients with the windowing method using the Rectangular Window function and convolution method? What utility or FIR design application can perform this ...
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43 views

Calculating SNR for ECG signals

I'm reading through the literature for finding the best way to calculate SNR for a ECG signal. While there are many algorithms for improving SNR, I couldn't find any that details any standard ...
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1answer
42 views

Understanding my Butterworth filter

My input is x and my filtered output is y. The sampling rate of x is ...
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2answers
32 views

Decimation of motion

I have a motion signal that you can think of as a sequence of pairs (x,y); what would be the best approach to decimate this sequence at real time? I haven't found anything similar on the web and I'm ...
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0answers
14 views

How complementary filter will remove gyro drift?

I just discovered the complementary filter and want to try it on a quadcopter. I can read that it should remove the gyro drift, but I don't really understand why... I created this simple Excel array: ...
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3answers
70 views

How to remove heart beats interference from pectoralis major electromyogram?

I am using electromyography to detect activity on pectoralis major, however I found an interference from heart beats that is affecting my posterior analysis. The sampling rate is 2000 Hz, and the time ...
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1answer
31 views

Problem to implement a sinusoid oscillator in matlab

I'm pretty new in dsp and I'm having tough times trying to get the output for a simple digital oscillator. I'm starting from the recursive formula $y[n]=x[n]+a \times y[n-1]-b \times y[n-2]$, and need ...
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1answer
24 views

MATLAB IIRs — extracting and scaling the coefficients of second order sections

suppose I generate the following filter: ...
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1answer
38 views

The two types of stability and “Why exponential”

When I was learning about LTI systems, I noticed that LTI system is said to be BIBO stable if and only if its square sum of impulse response is finite. This expression is found on many textbook of ...
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1answer
31 views

Is it possible to know the order of the filter, just looking on the pole zero plot?

is it possible to know the order of the filter, just looking on the pole zero plot. I know how to get the order of the filter using calculations(highest order), but I want to know is it possible to ...
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1answer
87 views

Common Filter Types for Audio Applications

I'm beginning to write a basic "virtual analog" synthesizer and want to implement a lowpass with variable cutoff frequency and resonance. Does anyone have insight into filter types commonly used to ...
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1answer
46 views

Frequency response of FIR (MTI delay line canceller) with non constant period

Short question How to plot the magnitude of frequency response of the delay line canceller with non constant period using GNU Octave? Or more directly: how to plot magnitude of frequency response of ...
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40 views

How to process the .wav file to get meaningful information like the number of inhales/exhales

The plot of the data from the wav file. Link to the sound file - https://drive.google.com/open?id=0BxAPlY66uX7qWWtDZUw3WkpjSGs&authuser=0 Also the FFT plot is like this I am new to the field ...
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0answers
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Transposing pitch profile of one audio on another

I have one audio file with rap music and one audio with sound record of my friend's reading some text. I want to transpose pitch profile of rap music on sound recording, is that possible? I can ...
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1answer
41 views

Recursive Implementation of the Gaussian Filter

I'm trying to implement an IIR form to approximate the Gaussian Blur Filter. I'm working with the article "Recursive Implementation of the Gaussian Filter" by Ian T. Young and Lucas J. van Vliet. ...
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2answers
41 views

Playing back an audio file at an arbitrary rate with upsampling and downsampling

Background: My overall goal is to create an audio file player which can playback an audio file at an arbitrary rate. The rate can change continuously as the file plays. This means upsampling to ...
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1answer
18 views

How to equalize frequency contents using filter?

Suppose there is a bounded continuous signal $f(t)$ that can be fourier-transformed into $F(\omega)$ of frequency contents. $|F(\omega)|$ is non-zero for only finite number of frequencies: ...
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16 views

Plotting Basis of 3D Steerable Filter

I am plotting isosurface plots of Basis of 3D Steerable filters which should look like Spherical Harmonics of first Zero, first and second order plots. Correct me ...
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1answer
21 views

How to manipulate attenuation in Parks MClellan algorithm?

I am using GNU Radio C++ source code in my app (pm_remez()) for generating FIR filters coefficients. Input parameters here are: ...
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1answer
61 views

How is the lowpass to bandpass transformation derived?

I'm using a lowpass to bandpass filter transformation: $$ s \leftarrow Q \left( \frac{s}{\omega_0} + \frac{\omega_0}{s} \right) $$ Based on the wiki article: ...
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1answer
45 views

just getting started in Signal Processing - easy question

I am reading Cycle Analytics for Traders by John Ehlers and need help. in the first section "Transfer Response" he refers to: so if I had $4$ prices say $8+8+8+8$ then average would be $8$ and ...
4
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3answers
180 views

Processing Accelerometer Vibration Data With FFT

For a project I am attempting to use an accelerometer to measure vibration in an RC aircraft and determine frequency from the result. To do this I am using an MPU-6000 accelerometer sampling @ 1000Hz. ...
2
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1answer
195 views

Don't understand coefficients in MATLAB “butter” low pass result

I don't unstand the nature of the output in Matlab's "butter" command. Calling [b,a] = butter(4, 0.5, 'low'); gives me two vectors, which the documentation says ...