# All Questions

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### Mixing two signals creates power at dc?

I have a signal with components at 1200 and 1800 Hz. When I mix this signal with a 1500 Hz signal to create components at -300 and +300 Hz (then LPF) a DC offset presents itself when the input signal ...
3 views

### Nth Order Differentiated Parabolic Wave Synthesis

I am working on a sound synthesis software project. At the moment I am working on an implementation of the "Differentiated Parabolic Wave" or DPW algorithm in C++, specifically a sawtooth ...
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### Confusion with applying hamming window to signal

I am writing some code which takes a signal of $n$ length, and processes it in $20$ ms chunks with $5$ ms of overlap... So basically I have a buffer of $20$ ms worth of sample data, and I am trying ...
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### embed a low-bitrate signal in a g.722 audio stream

I would like to embed a small code (<16 bits) in an audio stream such that it can be recovered after g.722 encoding. It is not particularly important that the code be inaudible, as long as the ...
6 views

### Constant-Q transform - summing complex DFT coefficients vs. summing DFT magnitudes

The constant-Q transform computes a spectrum on a logarithmic frequency axis. When analyzing music signals, this can be a more meaningful representation than the Discrete Fourier Transform (DFT), as ...
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### Trending work on phase locked loop in optical communication

I am just researching more on PLL and its use in several different ways. I have gone through the basics, PLL as demodulator and phase detector and coherent detector and few more..... In IEEE i can ...
14 views

### how to code fir filter in matlab using discrete equation?

I want to design a fir filter in matlab using the discrete equation. I won't be using any built in functions. For doing so what will be the coefficient? How can i compute it?
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### Correlation between Sin and Square wave

I would like to know how $\frac T2$ came for time period in the image below.Because I think the frequncy is 1 so time period should be 1.Is that correct? or can anyone help me.. The article from ...
32 views

### Design a Filter with Resonance

I want to design a Filter with a variable Cutoff Frequency and Resonance. However in the source I'm using there is a Bi-Quad Filter with two IIR and two FIR Filters designed like this : ...
14 views

### What would happen if I perform histogram equalisation on average RGB

In Image signal processing, I'm trying to figure out what would be the consequences of performing a histogram equalisation on the average of the 3 channels (R,G,B). I'm trying to conclude some ...
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### Variance of white noise and the STFT

I hope someone can help me understand the meaning of variance in this case. I am reading an old research paper by Ephraim and Malah (for my DSP project) and it says: Knowing that $D_k$ is the FFT ...
22 views

### Limit of DFT from zero to N-1:

Why do we take the limit of DFT from 0 to N-1? If signal exists from let say -5 to 8. Then what will be the limit and how will we calculate DFT?
28 views

### Detecting changes between two similar images

I have the following problem: I need to detect changes between two more or less similar image. In that case, I want to detect the missing parts. Lets assume that the displacement is no more that ...
6 views

### DFT of 2d matrix only along one direction

I have a 100 X 800 matrix. I want to do a DFT along each row. That is, for each of the 100 rows, I want to do a DFT of the 800 elements. How do I go about this (in FORTRAN) .
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### Decompose an image into better compressible components

Our team develops an application that, in some feature, connects to a scanner (via TWAIN or WIA) and scans a document, and makes a PDF file out of it. The application is mostly used to process mail or ...
127 views

### Is it necessary to downsample data for filtering of low frequencies?

My data is sampled at $f_s = 32kHz$, and for a particular analysis I'm only interested in signals with certain frequencies from $f_{highpass} = \text{0.1Hz}$ to $f_{lowpass} = \text{300 Hz}$. When I ...
27 views

### Audio processing — difference between block and sample-by-sample?

If a system operates on a signal with a time-domain IIR or FIR, why would an acquisition system chunk the audio into powers of two? I can understand filling a buffer by a power of two for an FFT ...
10 views

### Feature extraction - DWT

I am new to DSP, I know a quite bit about Python. I have started to code to classify audio (wav files) ...
53 views

### Question on Chebyshev filter

What does the output signal look like when you insert $2000 Hz$ square pulses to chebyshev filter with parameters: (Matlab syntax). I tried to do it like this but I don't understand where it goes ...
21 views

### QC-LDPC Decoder - Is it a codeword?

I'm designing a QC-LDPC decoder in VHDL. It uses a layered decoding method - only a single block row of parity equations is evaluated each iteration (the bit values are still updated every iteration). ...
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### FFT widow to dsp processor. ff meaning fft

I am applying 8 samples and triangular window to my fft engine. I am getting the results but not accurate (approximately equal with some tolerance). I am calculating MATLAB reference as below : ...
23 views

### Removing self-emitted background noise from audio

I've been working with speech recognition and kinect lately. Now i made a simple media player I can control by speech. It works pretty good (thanks to Kinects AEC?) but not quite reliable. Now I ...
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### How to design a filter with custom group delay — why is it an IIR?

Say I have an FIR filter with desired magnitude characteristics. I could imagine using an allpass IIR in series with the FIR to alter the group delay characteristic to provide both a 'magnitude ...
24 views

### algorithm for low frequency filter and analysis

i have a number of analog signals being monitored and then compared. My issue is that the signals are not synchronized (potentially 4-5 seconds out of phase) and my target "trouble" frequency is much ...
44 views

### What does the graph of audio signal tells? what are negative samples?

What does the graph of audio signal tells? what are negative samples?
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### Template matching results when the template is not on the original image

For testing purposes I'm building a bot that clicks on buttons in the screen. I have a folder with all the possible buttons that needs to be pressed and the application being tested only has one ...
110 views

### Audio EQ Cookbook without frequency warping

The famous http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt offers a set of [real] biquad filter calculation formulas that generally work fine. However, when filter's frequency approaches Nyquist ...
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### Wave-time trace to Amplitude and PSD spectrum

For a project I’m currently working on, I composed a irregular ocean wave (function of time) by the summation of n regular waves. For the validation and further processing I’d like to produce the ...
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### How to choose sampling rate?

I am working on a FMCW radar and I want to sample the I/Q signals from the 2 receiving antenna (total 4 channels) simultaneoulsy and send the digital data to computer to extract range and velocity ...
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### Why voiced/unvoiced speech classification is important?

I am building a voice activity detection algorithm, the input contains phone calls. What I am trying to do is to predict when there is speech activity or not, the features I am using are: Zero ...
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### filter design for ECG

I would like to ask how to design a digital filter to remove $50$ Hz interference on an ECG signal. Do I need to use notch filter? Thanks.
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### Generate band limited white noise to be used as excitation in ODE

I am trying to repeat an example I found in a paper. I have to solve this ODE: $25 \ddot{x} + 15 \dot{x} + 330000 x = p(t)$ where $p(t)$ is a white noise sequence band-limited into the 10-25 Hz ...
25 views

### Image processing: Importance of phase

I was doing some experiment on image processing. I wanted to explore the importance of phase and Magnitude. I followed the following approach: Take 2 image of same dimension. Apply Fourier ...
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### Why do we use Hilbert Transform in discrete time domain?

I have few questions regarding hilbert transform, Questions are as follows: 1)What are the benifits of using hilbert transform hardware and software point of view? 2)Cannot we use any other digital ...
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### spread spectrum communication in airport

Does anyone know , how the spread spectrum sequences are used in airports. I've attended a presentation this morning regarding spread spectrum in my college, the author mentioned that the sequences ...
16 views

### Bit Plane Complexity Segmentation (BPCS)

I am working in digital image steganography. Although I am novice but implemented some of LSB substitution based steganographic methods. Now want to implement Bit Plane Complexity Segmentation ...
28 views

### How to calculate SNR of noisy signal?

Say, I have a noisy signal (clean signal + AWGN). When I pass this signal through my noise reduction program, I get the clean signal. My question is how to calculate the SNR before and after passing ...
15 views

### Continuous wavelet function spanning piecewise functions

Is there a continuous wavelet function that spans the space of piecewise: linear functions (as Haar wavelet spans the space of piecewise constant functions). polynomial functions?
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### Wiener filter of two signals of comparable magnitude

Suppose I have two signals, x(t) and y(t) (e.g. from a Lock In amplifier, such that x(t) and y(t) are 90 deg. out of phase). Assume x(t) is the clean signal, s(t), plus background noise, while y(t) is ...
33 views

### Removing the mean in finding PSD

Does removing the mean value of the signal effect the estimation of power spectral density(PSD)? If it effects, how? What is the advantage we can get by removing the mean of the signal in estimating ...
13 views

### Definition of Cohen's class

The Cohen's class is defined as a class of time-frequency quadratic energy distributions which are covariant by translations in time and in frequency. Can please someone explain why the invariance by ...
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### Problem in Implementing Cyclostationary Feature Detector in Matlab

I have Implemented this detector in AWGN channel in Matlab but I am getting vague result. As it performance doesn't vary with change in SNR. Its very strange result for me. I don't know what mistake I ...
13 views

### Structured light 3D imaging

i am currently working on structured light 3-D imaging, i have read no of journal papers but still i am not getting practical approach of the subject. Especially how to use triangulation principle, I ...
32 views

### Does the system matrix being singular tell us anything about the system?

If we have a linear system, represented in State Space and the A matrix is singular (det(A) == 0), can we expect any special properties from the system?
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### Downsampling fft results to a graphics display

I'm new to dsp. I've got a complex signal that was sampled at 192kHz then an fft of 16384 bins created. This now needs to be plotted on a graph for a real time spectrum display. The problem is if ...
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### Modulation and DeModulation

I have a question regarding Modulation and Demodulation. In question 5.21 (b) from the "Discrete-time Signal Processing" book by Oppennheim, he asks to find out the type of filter used in the attached ...
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### Conceptual question on FFT and chirp signal

If I take the FFT of a sinusoid I will get a plot whit all the energy of the signal concentrated at the sinusoid frequency. But what happens if I have a signal in which the frequency keeps ...
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### Time Frequency Signal Analysis in Mathematica (MMA)

I want to know " Whether there is any Tool Box in Mathematica (MMA) for the Time-Frequency (TF) Signal Analysis". I am well-versed in MMA Programming, so want to do TF Signal Analysis in MMA. I think ...