# Signal and Image Processing

**URL:** https://discourse.julialang.org/c/domain/dsp/26.md?page=1

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**Page:** 2

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## [OpenCV function signatures](https://discourse.julialang.org/t/opencv-function-signatures/123145)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 1\
**Last updated:** [December 3, 2024, 12:10pm UTC](https://discourse.julialang.org/t/opencv-function-signatures/123145 "2024-12-03T12:10:02Z")

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I’m trying to use the camera calibration functions in OpenCV.jl, but I can’t create arguments that would fit some of the functions’ signatures. For example one of OpenCV.calibrateCamera’s method signatures is: OpenCV.c…

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## [Bode plot of DSP filter?](https://discourse.julialang.org/t/bode-plot-of-dsp-filter/122845)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 5\
**Last updated:** [November 25, 2024, 7:48pm UTC](https://discourse.julialang.org/t/bode-plot-of-dsp-filter/122845 "2024-11-25T19:48:00Z")

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I designed a discrete Butterworth filter using the DSP package. How can I create a Bode plot of the transfer function? using DSP function create\_filter(cut\_off\_freq; order=4, type=:Butter, dt) if type == :Butter …

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## [How to get the a and b coefficients out of the DSP digital filter function?](https://discourse.julialang.org/t/how-to-get-the-a-and-b-coefficients-out-of-the-dsp-digital-filter-function/122516)

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**Author:** [@Nine\_Cycles](https://discourse.julialang.org/u/Nine_Cycles)\
**Replies:** 2\
**Last updated:** [November 11, 2024, 10:15pm UTC](https://discourse.julialang.org/t/how-to-get-the-a-and-b-coefficients-out-of-the-dsp-digital-filter-function/122516 "2024-11-11T22:15:47Z")

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Hello, i want to get the a and b coefficients of a digital Butterworth filter in Julia. I have to iteratively compute the results for live-sound purpose, so I cannot use a filter() function. Here is where my code is at …

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## [Help with NUFFT (NFFT) vs FFT in Radial MRI applications](https://discourse.julialang.org/t/help-with-nufft-nfft-vs-fft-in-radial-mri-applications/122106)

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**Author:** [@matividalg](https://discourse.julialang.org/u/matividalg)\
**Replies:** 0\
**Last updated:** [November 1, 2024, 12:52am UTC](https://discourse.julialang.org/t/help-with-nufft-nfft-vs-fft-in-radial-mri-applications/122106 "2024-11-01T00:52:02Z")

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Hi there! I have a few problems when generating a “fHat” matrix of a NFFT (using package NFFT) vs when dealing with the inverse fft of my own (imperfect) adquisition. Let me illustrate. I’m simulating a regular Gradient…

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## [Julia Images adaptive histogram equalization vs MATLAB's implementation](https://discourse.julialang.org/t/julia-images-adaptive-histogram-equalization-vs-matlabs-implementation/119469)

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**Author:** [@cpaniaguam](https://discourse.julialang.org/u/cpaniaguam)\
**Replies:** 1\
**Last updated:** [September 21, 2024, 1:04pm UTC](https://discourse.julialang.org/t/julia-images-adaptive-histogram-equalization-vs-matlabs-implementation/119469 "2024-09-21T13:04:55Z")

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I’m hoping to get an expert’s opinion on this matter. In MATLAB: \>\> img = imread('cameraman.tif'); \>\> class(img) ans = 'uint8' \>\> sum(img(:)) ans = 7780728 \>\> img\_eq = adapthisteq(img, Range="original", …

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## [Keypoint based image registration using ImageTransformations.jl warp](https://discourse.julialang.org/t/keypoint-based-image-registration-using-imagetransformations-jl-warp/119158)

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**Author:** [@LorMam](https://discourse.julialang.org/u/LorMam)\
**Replies:** 1\
**Last updated:** [September 12, 2024, 10:23am UTC](https://discourse.julialang.org/t/keypoint-based-image-registration-using-imagetransformations-jl-warp/119158 "2024-09-12T10:23:50Z")

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I have given two images that I want to warp on top of on another based on a number (here 6) of key points. The key point coordinates are measured using ImageJ. First, I load the images, and the key points. using …

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## [How to warp large arrays (Tiff stacks) efficiently?](https://discourse.julialang.org/t/how-to-warp-large-arrays-tiff-stacks-efficiently/119107)

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**Author:** [@gltchr](https://discourse.julialang.org/u/gltchr)\
**Replies:** 3\
**Last updated:** [September 6, 2024, 11:24am UTC](https://discourse.julialang.org/t/how-to-warp-large-arrays-tiff-stacks-efficiently/119107 "2024-09-06T11:24:22Z")

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Hello, In order to avoid the XY-problem I will try to provide a context and a desired result first, and only later some particular questions. Context: I don’t have much experience in Julia and (partially in order to f…

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## [Join me for a mini review of signal analysis tools for physiology and open science](https://discourse.julialang.org/t/join-me-for-a-mini-review-of-signal-analysis-tools-for-physiology-and-open-science/115344)

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**Author:** [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Replies:** 9\
**Last updated:** [September 2, 2024, 9:48pm UTC](https://discourse.julialang.org/t/join-me-for-a-mini-review-of-signal-analysis-tools-for-physiology-and-open-science/115344 "2024-09-02T21:48:37Z")

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Hi there, Following a review of our paper for ComplexityMeasures.jl, I’ve been invited to contribute to the issue: because I am swamped with work, I decided to contribute a mini review focusing on Julia-based tools f…

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## [How to set the number of scales output of Wavelets.jl](https://discourse.julialang.org/t/how-to-set-the-number-of-scales-output-of-wavelets-jl/117251)

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**Author:** [@bryaan](https://discourse.julialang.org/u/bryaan)\
**Replies:** 0\
**Last updated:** [July 19, 2024, 6:34pm UTC](https://discourse.julialang.org/t/how-to-set-the-number-of-scales-output-of-wavelets-jl/117251 "2024-07-19T18:34:32Z")

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By default for my signal Wavelets.jl cwt is giving 28 columns in the output Y matrix. How can I set this to a constant number of columns no matter the signal? using Wavelets Y = Wavelets.cwt(signal, wavelet(WT.dog2))

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## [DSP.jl - digitalFilter - no matching method when using 'fs' as argument](https://discourse.julialang.org/t/dsp-jl-digitalfilter-no-matching-method-when-using-fs-as-argument/117130)

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**Author:** [@funboat](https://discourse.julialang.org/u/funboat)\
**Replies:** 3\
**Last updated:** [July 17, 2024, 12:19pm UTC](https://discourse.julialang.org/t/dsp-jl-digitalfilter-no-matching-method-when-using-fs-as-argument/117130 "2024-07-17T12:19:22Z")

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Hi, Julia v1.10.4 DSP v0.7.9 I was trying to create a digital filter using the example code, and get the following error. https://github.com/JuliaDSP/DSP.jl/blob/76001f4f863f43df6b5ee48575e77f3dd3fe3941/docs/src/filt…

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## [32-bit TIFs?](https://discourse.julialang.org/t/32-bit-tifs/116931)

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**Author:** [@EricChameroy](https://discourse.julialang.org/u/EricChameroy)\
**Replies:** 2\
**Last updated:** [July 12, 2024, 5:47pm UTC](https://discourse.julialang.org/t/32-bit-tifs/116931 "2024-07-12T17:47:49Z")

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Hello, Is it possible to save images as 32-bit TIFs? When attempting to save Float32 matrices using TiffImages.jl, I only get 8-bit TIFs. Thanks!

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## [How to accelerate the imfiter() operation?](https://discourse.julialang.org/t/how-to-accelerate-the-imfiter-operation/102965)

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**Author:** [@RunguangLi](https://discourse.julialang.org/u/RunguangLi)\
**Replies:** 8\
**Last updated:** [July 8, 2024, 11:06am UTC](https://discourse.julialang.org/t/how-to-accelerate-the-imfiter-operation/102965 "2024-07-08T11:06:53Z")

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My task contains hundreds of thousands of convolution operations like the following one. Each cost 11s now. I wonder if anyone can help to accelerate it. using ImageFiltering @time imfilter(Float32, rand(Int8, 300, 300,…

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## [Compare ifft in Matlab with Julia for complex input](https://discourse.julialang.org/t/compare-ifft-in-matlab-with-julia-for-complex-input/116002)

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**Author:** [@Jake](https://discourse.julialang.org/u/Jake)\
**Replies:** 3\
**Last updated:** [June 22, 2024, 1:45pm UTC](https://discourse.julialang.org/t/compare-ifft-in-matlab-with-julia-for-complex-input/116002 "2024-06-22T13:45:18Z")

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My use case is frequency demodulation using the method of Coats and Randall, with the link being one of many from a web search. They use the Hilbert transform for this purpose. When I use ifft in MATLAB on a complex ve…

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## ["scrubbing" sound: playing sound from views rather than Arrays](https://discourse.julialang.org/t/scrubbing-sound-playing-sound-from-views-rather-than-arrays/115957)

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**Author:** [@sadish-d](https://discourse.julialang.org/u/sadish-d)\
**Replies:** 0\
**Last updated:** [June 21, 2024, 1:02am UTC](https://discourse.julialang.org/t/scrubbing-sound-playing-sound-from-views-rather-than-arrays/115957 "2024-06-21T01:02:11Z")

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In PortAudio, audio data is just a Nx1 (mono) or Nx2 (stereo) matrix with an associated sample rate. So if you had a sample rate of 44\_100 samples per second, a one-second-long audio will have 44\_100 rows. Say I have tw…

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## [Use the homography matrix from Apriltag](https://discourse.julialang.org/t/use-the-homography-matrix-from-apriltag/114824)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 0\
**Last updated:** [May 28, 2024, 9:38am UTC](https://discourse.julialang.org/t/use-the-homography-matrix-from-apriltag/114824 "2024-05-28T09:38:43Z")

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This is just to share a piece of a code that might prove useful for someone. If you want to use the homography matrix from a detected Apriltag (such as the ones from Apriltags.jl), in order to convert from pixel coordin…

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## [Is it time to make a pure Julia FFT?](https://discourse.julialang.org/t/is-it-time-to-make-a-pure-julia-fft/99256)

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**Author:** [@Tarny\_GG\_Channie](https://discourse.julialang.org/u/Tarny_GG_Channie)\
**Replies:** 14\
**Last updated:** [May 8, 2024, 3:21pm UTC](https://discourse.julialang.org/t/is-it-time-to-make-a-pure-julia-fft/99256 "2024-05-08T15:21:13Z")

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While FFTW is great, it is a GPL-licensed C library. R, Mathematica, Python’s Scipy, etc have their own FFT library. Should we finally have our own FFT library? A pure Julia FFT may provide several advantages such as bei…

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## [Is there a Package for EVM calculation and constellation diagram visualization in digital communications?](https://discourse.julialang.org/t/is-there-a-package-for-evm-calculation-and-constellation-diagram-visualization-in-digital-communications/113905)

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**Author:** [@Trailing3208](https://discourse.julialang.org/u/Trailing3208)\
**Replies:** 0\
**Last updated:** [May 6, 2024, 1:57pm UTC](https://discourse.julialang.org/t/is-there-a-package-for-evm-calculation-and-constellation-diagram-visualization-in-digital-communications/113905 "2024-05-06T13:57:26Z")

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Hello there, I’m currently trying to implement some digital communications simulation and there are a bunch of helpful packages such as DSP.jl as well as DigitalComm.jl, but as far as I know there is no implementation o…

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## [Parallel resampling columnwise](https://discourse.julialang.org/t/parallel-resampling-columnwise/113203)

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**Author:** [@jafagervik](https://discourse.julialang.org/u/jafagervik)\
**Replies:** 2\
**Last updated:** [April 20, 2024, 10:48pm UTC](https://discourse.julialang.org/t/parallel-resampling-columnwise/113203 "2024-04-20T22:48:43Z")

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Hi, I have a large matrix I want to resample. Typical size is about 20\_000 \* 500. The code I have for now looks like this: using DSP: resample function resample\_parallel(signal::Matrix{Float32}, rate::Real) result …

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## [Undistort Points in Julia](https://discourse.julialang.org/t/undistort-points-in-julia/113027)

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**Author:** [@dennispureza](https://discourse.julialang.org/u/dennispureza)\
**Replies:** 1\
**Last updated:** [April 16, 2024, 6:50pm UTC](https://discourse.julialang.org/t/undistort-points-in-julia/113027 "2024-04-16T18:50:45Z")

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Hello everyone, I was looking for a Julia package with a function to undistort image points like Matlab’s undistortPoints(), and since I couldn’t find any, I am currently trying to code a function myself.I already have …

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## [Weird phase result between two simple sine curves](https://discourse.julialang.org/t/weird-phase-result-between-two-simple-sine-curves/111769)

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**Author:** [@PeX](https://discourse.julialang.org/u/PeX)\
**Replies:** 12\
**Last updated:** [March 18, 2024, 7:32pm UTC](https://discourse.julialang.org/t/weird-phase-result-between-two-simple-sine-curves/111769 "2024-03-18T19:32:41Z")

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Hi all, I’m trying to get the relative phase between two simple sine series: I’m trying to use FFTW to get their angle from the dominant frequency and calculate the relative phase: function FFT\_phase\_rel(sig1, sig2,…

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## [Allocation-less, perhaps planned, Constant Q transform](https://discourse.julialang.org/t/allocation-less-perhaps-planned-constant-q-transform/111694)

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**Author:** [@Benny](https://discourse.julialang.org/u/Benny)\
**Replies:** 1\
**Last updated:** [March 16, 2024, 1:40pm UTC](https://discourse.julialang.org/t/allocation-less-perhaps-planned-constant-q-transform/111694 "2024-03-16T13:40:57Z")

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I’m reading up on FFTs and STFTs again for 1D real data, and eliminating startup work and allocations with rFFT plans looks promising. I’m also interested in spacing the frequency bins logarithmically like how musical pi…

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## [Scipy.signal.iirfilter equivalent in DSP.jl and more](https://discourse.julialang.org/t/scipy-signal-iirfilter-equivalent-in-dsp-jl-and-more/110783)

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**Author:** [@scelles](https://discourse.julialang.org/u/scelles)\
**Replies:** 3\
**Last updated:** [February 26, 2024, 8:46pm UTC](https://discourse.julialang.org/t/scipy-signal-iirfilter-equivalent-in-dsp-jl-and-more/110783 "2024-02-26T20:46:15Z")

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Hello, I did some DSP about 20 years ago but didn’t tackled that field recently. In order to get back to it I’m planning to build some Pluto.jl notebooks in this field. I found this blog post Applying digital filters …

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## [Need access to ImageInpainting.jl](https://discourse.julialang.org/t/need-access-to-imageinpainting-jl/110404)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 3\
**Last updated:** [February 26, 2024, 11:10am UTC](https://discourse.julialang.org/t/need-access-to-imageinpainting-jl/110404 "2024-02-26T11:10:54Z")

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I wrote this package a long time ago, when I co-founded JuliaImages. I am not an org owner anymore, and can’t access the repository settings to fix TAGBOT keys. Can an owner of JuliaImages please help fix this? I want t…

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## [Rolling (time) average of a timeseries of images](https://discourse.julialang.org/t/rolling-time-average-of-a-timeseries-of-images/110352)

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**Author:** [@JonathanH](https://discourse.julialang.org/u/JonathanH)\
**Replies:** 3\
**Last updated:** [February 19, 2024, 9:59am UTC](https://discourse.julialang.org/t/rolling-time-average-of-a-timeseries-of-images/110352 "2024-02-19T09:59:36Z")

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Hi all, I am new to Julia, and this may be a very straightforward question. I have a timeseries of images, and I am trying to calculate a pixel-wise rolling time average. The obvious choice for doing this would be the m…

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## [How to implement a filtered derivative](https://discourse.julialang.org/t/how-to-implement-a-filtered-derivative/109441)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 29\
**Last updated:** [February 3, 2024, 10:51pm UTC](https://discourse.julialang.org/t/how-to-implement-a-filtered-derivative/109441 "2024-02-03T22:51:18Z")

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How can I implement a filtered, discrete time derivative following the equations: u\_1 = u − y\_1 dy\_1/dt = (1 / T\_D) \* u\_1 y = (K\_D / T\_D) \* u\_1 filtertau = 0.01 as described on page 128 of the following document: http…

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## [How to implement Lyons’ Differentiator](https://discourse.julialang.org/t/how-to-implement-lyons-differentiator/109438)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 5\
**Last updated:** [January 30, 2024, 5:28pm UTC](https://discourse.julialang.org/t/how-to-implement-lyons-differentiator/109438 "2024-01-30T17:28:19Z")

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Hello, I am trying to implement a discrete time differentiator, Lyons’ Differentiator type two, see: Design of a Discrete-Time Differentiator | Wireless Pi It has five coefficients. How would you implement that? This …

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## [How to calculate the real cepstrums of a time-series in Julia?](https://discourse.julialang.org/t/how-to-calculate-the-real-cepstrums-of-a-time-series-in-julia/109169)

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**Author:** [@Shayan](https://discourse.julialang.org/u/Shayan)\
**Replies:** 6\
**Last updated:** [January 27, 2024, 10:01am UTC](https://discourse.julialang.org/t/how-to-calculate-the-real-cepstrums-of-a-time-series-in-julia/109169 "2024-01-27T10:01:25Z")

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That being said, the real cepstrum of a time series can be calculated by the inverse Fourier transform of the real logarithm of the Fourier transform of the time–series (K. Kalpakis et al., 2001). Let’s assume that w…

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## [Determine the delay between two signals](https://discourse.julialang.org/t/determine-the-delay-between-two-signals/109140)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 12\
**Last updated:** [January 24, 2024, 7:39pm UTC](https://discourse.julialang.org/t/determine-the-delay-between-two-signals/109140 "2024-01-24T19:39:51Z")

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Hello, I am trying to find out the delay between two signals. I have the following Python example: # Cross-correlate correlation = correlate(x, y, 'full') # Get the lag vector that corresponds to the correlation vect…

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## [\[Images.jl\] Projective Transform based on Matrix](https://discourse.julialang.org/t/images-jl-projective-transform-based-on-matrix/108559)

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**Author:** [@lgmendes](https://discourse.julialang.org/u/lgmendes)\
**Replies:** 2\
**Last updated:** [January 15, 2024, 6:43am UTC](https://discourse.julialang.org/t/images-jl-projective-transform-based-on-matrix/108559 "2024-01-15T06:43:18Z")

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How I can apply an Projective Transform (or an Affine) to a image based on a transform matrix ? In phyton I can do this using: tform = transform.ProjectiveTransform(matrix=matrix) An example in Python (from Documentat…

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## [SIGVIEW - interface with DAQ via JULIA](https://discourse.julialang.org/t/sigview-interface-with-daq-via-julia/108202)

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**Author:** [@Jawad\_Malik](https://discourse.julialang.org/u/Jawad_Malik)\
**Replies:** 8\
**Last updated:** [December 31, 2023, 5:46pm UTC](https://discourse.julialang.org/t/sigview-interface-with-daq-via-julia/108202 "2023-12-31T17:46:51Z")

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I am working on a Condition Based Monitoring System for a small Marine Vessel. Need a FFT Software at the end of the line to keep a check on the Diesel Engines. I have four sets of Piezo + DAQ to pick up vibrations; 24…

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