Questions tagged [distortion]

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image preprocessing(filtering) : before or after undistortion and stereo rectification

I'm currently working on a stereo visual-slam program (using OpenCV). After I get the images, there are 2 preprocessing steps to be done : A) Undistort the images + stereo rectification B) Some ...
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2 answers
39 views

Fixing distortion in photographic reproductions

I am currently building a photographic setup which I intend to use to make reproductions of a large amount of transparencies(positive and negative film strips). As I will be using a fairly small (1&...
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3 votes
1 answer
57 views

Advice on seperation of impulse responses for harmonic distortion orders

I am working based on Angelo Farinas paper: Simultaneous measurement of impulse response and distortion with a swept-sine technique. The purpose of the work is part of a loudspeaker measurement and ...
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5 votes
2 answers
302 views

Group delay compensation for non coincident drivers

Suppose I have a two-way speakers system which can be modeled as a two-way Linkwitz-Riley crossovers network with impulse responses $h_{lp}(n)$ and $h_{hp}(n)$. I would like to equalize the group ...
2 votes
1 answer
77 views

What happens when filter ringing is far longer than the signal itself?

I'm digging into some (quite popular in my field) analytical practice that I find suspicious. The problem is to remove the trend from some very short (eg. 18-40 data points representing 200 - 800 ms) ...
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1 answer
78 views

Signs of waveshaping polynomial coefficients

I'm playing with some basic functions for distortion purposes. Odd order polynomials generate odd harmonics, even order polynomials generate even harmonics. When I combine them, both types occur at ...
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0 answers
32 views

How to do stretching Image distortion transformation

I have an assignment to transform an image like this: I have done with twirling, fisheye, bulge, but I'm having a hard time finding the right formulas for those effects. here is my code for twirling: ...
1 vote
0 answers
31 views

Deconvolution of signal with harmonic distortion

I came across these measurements done using a stepped sine sweep covering only some frequencies (~800 frequency points). I would like to get an impulse response from these measurements to convolve ...
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59 views

Emulating tape distortion of low-level audio signals

I'm working on a tape echo emulation in Reaktor, and I've based the frequency response, tape speed warble, high-amplitude saturation and tape hiss on a paper I found about the Roland Space Echo. ...
-1 votes
1 answer
61 views

Error correcting code? - using RGB space with a lookup table

This problem could be thought about as how to transmit a signal with 3x8bit RGB in a way that is robust to the distortion of antialiasing blends colors. The context: I need to rewrite a short utility ...
0 votes
1 answer
61 views

High FIR order in time critical classification task

I have a question regarding filtering (bandpass in my case) as a preprocessing step before a classification task. The frequency band I am interested in lies between 0.5 - 22 Hz which results in a ...
1 vote
2 answers
162 views

Can harmonics be created or simulated a la carte

I am trying to learn about adding harmonics (audio) with a goal to make a plugin that can allow adjustment of the amplitude of each harmonic being added. I would not have the ability to write this but ...
1 vote
1 answer
57 views

Fixing integer overflow in wave file

I have this recording from my DAW that showed a strange form of distortion: the signal clipped at many places, but instead of simply being clipped (loss of information), somehow the integer value of ...
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6 votes
1 answer
107 views

Finding the Transfer Function of a Multiplicative Distortion in MATLAB

I have the frequency response of two signals shown above. One is uncontaminated, and the other is the same signal contaminated by a multiplicative distortion with two poles and two zeros. I need to ...
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3 votes
0 answers
545 views

How does image rotation affect the intrinsic camera parameters?

I am considering the problem of how to (manually) change camera model parameter to make it "valid" on a rotated image. This question tackles resizing, but does not consider lens distortion. ...
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2 votes
2 answers
154 views

Exponential Swept Sine Distortion

I was able to get passable results on fundamental measurements using and exponential swept sine. Now I am trying to get distortion information from the same measurement but am puzzled by the results. ...
1 vote
1 answer
36 views

Signal distortion under non-linear channel

The channel is given to have these characteristics, and its required to study the affect on Frequency Modulated signal and its demodulation. Since there are no sharp corners (like during clipping) ...
-1 votes
1 answer
574 views

What function to apply a Metamorphopsia (grid warp) translation?

How would I go about finding or creating a function to warp images dependent on grid lines surrounding an origin (I don't wish for a grid on my actual images): It should work in practically the same ...
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1 answer
102 views

Understanding legacy code: Algorithm to remove radial lens distortion

The method below to remove lens distortion from a camera was written more than ten years ago and I am trying to understand how the approximation works. ...
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1 answer
116 views

Total Harmonic Distortion THD for the rectifier

I have a circuit with rectifier and this cause the non-linearity and consequently harmonic. I show it on the oscilloscope and then collect the signal from the oscilloscope to the computer by using the ...
5 votes
1 answer
297 views

Group Delay for Hilbert Transformer and Resulting Dispersion

An ideal Hilbert Transformer shifts the phase for all positive frequencies by $-\pi/2$ and all negative frequencies by $+\pi/2$ while maintaining constant magnitude everywhere. Group Delay is the ...
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1 answer
113 views

How to quantify phase distortion of a filter specific to a signal?

For example, a EKG input signal is filtered with a known transfer function that does not have linear phase. How do you quantify the phase distortion of the output signal given you have the input? I ...
1 vote
1 answer
824 views

How to prevent distortion after down-sampling?

I am new to audio signal processing, but in one of my machine learning projects that I am working on, I need to down-sample my audio somewhere in the middle of my neural network. Therefore, I need a ...
0 votes
0 answers
979 views

How to measure SINAD of an audio signal?

I tried to measure the SINAD and SNR of a recorded audio signal using MATLAB. The following is the process I did to measure the 2 parameters: Firstly, I generated an FM modulated signal(1 kHz audio ...
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2 votes
1 answer
193 views

Distort voice to hide talker identity as much as possible

I need to develop an app which makes speech recognition. Because I need to be able to constantly improve the recognition capability, I would like to train the engine with real recordings and match the ...
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1 answer
168 views

Recommendations for SINAD equipment

I am interested in buying a device that measures the SINAD of the audio signal(FM signal) that I receive from PC. Here is the setup: Signal generator (generating 1kHz FM signal ) $\rightarrow$ ...
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Any recommendations for buying SINAD measuring equipment? [duplicate]

I am interested in buying a device that measures the SINAD of the audio signal(FM signal) that I receive from PC. Here is the setup : Signal generator -> attenuator ->HackRF connected to PC with SDR# ...
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1 vote
1 answer
449 views

Linear vs Non linear distortion

I'm learning about distortion and I got stuck at "What is the difference between linear and non-linear distortion?" (Also in frequency spectrum i.e. Amplitude and phase spectrum)
5 votes
3 answers
949 views

Precise 5th and 7th harmonics of a sampled sine wave

Does anyone know in decibels (to 1/100th of a dB) what the theoretical 3rd, 5th and 7th harmonic of a 0dB fs 24-bit (i.e. full-level; 0dB = -8,388,607 to 8,388,607) sampled sine wave without dither ...
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1 vote
1 answer
477 views

Can I use SINAD for THD+N measurements? Are they inverse of each other?

I'm looking for a clarification, which I haven't really been able to find. It's probably obvious but I'd like to be absolutely sure of what I'm calculating. I noticed that the formula that calculates ...
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0 votes
2 answers
58 views

Audio sounds oddly distorted [closed]

https://clips.twitch.tv/TangentialObliqueLobsterSaltBae https://clips.twitch.tv/CharmingBashfulAlfalfaRickroll https://clips.twitch.tv/NaiveKindGorillaGivePLZ (Disclaimer: These were not recorded on ...
-1 votes
1 answer
212 views

Finding the memory polynomial model coefficients

I want to build a memory polynomial model given that I know the corresponding output signals for known input signals. What is the easiest way to find the coefficients of it? And how do we take the ...
0 votes
1 answer
405 views

Dithering adds harmonic distortion after filtering and upsampling

I have an issue which I wasn't able to solve for a few days. I have implemented a polyphase FIR interpolation filter within an FPGA which does interpolate by a factor of 8 or 16 times. I do accept an ...
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0 votes
2 answers
130 views

Why is distorted / quantized white noise still white noise?

White noise can be created by setting every sample in the time domain to a random number with a gaussian distribution. Every sample is random, so the frequency response is obviously random. Easy ...
4 votes
1 answer
500 views

Identify the Type of Image Distortion (On Lena Image)

I want to understand the distortions in each of the lena images shown in the image below. I see that the first one is a blur. How can undo the blur. The second one is colored salt and pepper noise. ...
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1 answer
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THD requirement for generated sine

I need to generate a sine signal using a DAC with a certain THD specification, say 0.1% @ 1KHz. As a first approach I’m considering it to be an ideal DAC along with an ideal LPF for aliasing removal ...
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5 votes
1 answer
467 views

Redistributing Color in a RGB Image According to a Gaussian Distribution

I haven't done this stuff in a while. If I have an image $I$ I can equalize the histogram of the image using some opencv procedure, it's already defined. Equalizing an histogram means essentially to ...
3 votes
1 answer
816 views

Can someone explain waveshaping to me?

Can someone explain waveshaping to me? I only know it shapes waveshapes by passing through some functions, but I don't yet understand e.g. what the plots (such as the following in Melda Production ...
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1 vote
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125 views

Calculating Transfer Functions From Harmonic Distortion Percentage

Hi I am working on emulating a piece of analog audio equipment and would like to be able to create a transfer function based on the measured percentages of harmonic distortion. I know that harmonic ...
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2 votes
0 answers
139 views

Wave Shaper Function From A Waveshaped Singal

Is there a way to work out an unknown waveshaper function, that was used to distort and map the values of an input signal to new output signal, form the output if we only have input signal and the ...
2 votes
1 answer
488 views

Norm MPEG-1 Layer III (Mp3) Filter banks distortion

So, I'm working with the filter banks used in Mp3, in Matlab. I am obtaining quite a huge distortion in the output and I don't really know whether I'm making something wrong. I've reviewed the ...
3 votes
2 answers
698 views

Digital modelling of circuits with diode (i.e. guitar distortion)

For the last few days I was struggling to come up with an idea how to model a guitar overdrive effect which works in realtime. One of the simplest circuit diagrams that produce it looks as follows: ...
3 votes
1 answer
207 views

Spectral baseline distortion simulation - Bruker smile

I work with Magnetic Resonance Spectroscopy data. Data (complex signals) obtained from Bruker scanners (one of the biggest manufacturers of MRS scanners) start with an important group delay - around ...
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2 votes
0 answers
542 views

Demodulation distortion in single-sideband and double-sideband

I am trying to compare the demodulation for single sideband (SSB) and dual sideband modulation formats (DSB) when the reconstructed carrier is not perfect (i.e. shifted in both frequency and phase). I ...
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3 votes
1 answer
367 views

Regarding the advantages of generalized linear phase filters

I know that for a linear-phase filter with frequency response given by $$H(e^{j\omega}) = |H(e^{j\omega})|e^{j\phi(\omega)} $$ if the input of the system is $$x[n] = s[n]\cos[\omega_0 n] $$ where $s[...
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1 vote
1 answer
101 views

Can IR emitter signal be distorted by curved glass housing around receiver?

I have built a garage door opening circuit that includes an IR sensor and an IR emitter (a remote control). When the IR sensor is in the open air it works fine. If I put the sensor inside a glass ...
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1 vote
1 answer
258 views

Create distortion from basic linear (and non-linear if neccessary) DSP elements

I'm studying mechatronics and I'm intrested in DSP basics. My lecturer said that there are four basic linear DSP elements: Adder (and other mathematical operations) Amplification (shown on diagrams ...
0 votes
1 answer
2k views

If a filter has a non-linear phase lag will the output signal be distorted?

EDIT: From here (https://www.mathworks.com/help/signal/ref/butter.html) it appears that an Butterworth filter has a non-linear phase lag at the normalized frequency of 0.5 onwards. Does that mean that ...
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Determine modulation function from spectrum?

I have a two periodic signals $x(t)$ and $y(t)$ which are related to each other by a periodic modulation function $\alpha(t)$: $$y(t) = \alpha(t) x(t)$$ If $x(t)$ is a sinusoid, is it possible to ...
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1 answer
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How to analyze image quality?

I have a few sequences of images, taken at fixed camera position, that address a moving object, which means the object moves towards the camera. But all the sequences of images are the cropped images ...
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