# All Questions

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### Sliding Windows, Global Image, Clustering and …?

Imagine that you have an algorithm that must detect some feature in an image. Right now, I know three "families" of search algorithms. Sliding Windows: You take a patch of some size (e.g. 15x15 ...
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### Re-recording audio vs. convoluting old audio data - differences?

I want to transform a studio audio dataset into a smartphone audio dataset (used for a speech recognition application). Would there be any difference in the resulting audio files using one of the ...
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### Is there a 3-dimensional correlate to phase residues?

In 2D phase unwrapping problems, the presence of a "phase residue" indicates that the answer obtained from a path-following unwrapping algorithm is dependent upon the path taken. A phase residue is a ...
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### Extracing IQ samples from a composite signal?

I'm writing a modulator in matlab to simulate IQ data that I would get from my radio to test my demodulator. I've read that I = x(t) * cos(wt) and Q = x(t) * cos(wt). What is the omega (w) term? If ...
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### why the number of filter coefficients in FIR filter has to be an odd number?

I calculated the order of the FIR filter to be 31(N). so, the number of coefficients has to be 32 (N+1). so, I have to increase it to 33 to make it an odd number. Why the number of filter ...
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### Comparing signals recorded using diffrent methods

Suppose we have two signals( focus to audio) recorded with different methods, or more simply, suppose we have two audio signals recorded with different microphone, and we want to confirm that these ...
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### Explain Shift property of DFT

Please check the link What effect does a delay in the time domain have in the frequency domain? Here it is said that if you delay your input signal by D samples, then each complex value in ...
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### What do you get appling FFT to Music?

I am trying to take a section of a song (approx 1.5 seconds) 44100 sample rate equals sample size of 65536 which is 2**16. I want to find the frequency of the piano note that is played in the window ...
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### Simplest approach to classify signal based on its 'smoothness'?

First of all, I have no experience with signal processing whatsoever and I may not even use proper terms so please bare with me. I am just humble software developer trying to find the simplest and the ...
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### Implementing image chroma keying with FIR filter in MATLAB

Is there any way I can apply the concept of FIR filters in chroma key composition, where I will remove a green background to focus on a subject and replace a different image on the removed part, sort ...
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### Confusion about speech being piecewise stationary

From wikipedia: "Modern general-purpose speech recognition systems are based on Hidden Markov Models. These are statistical models that output a sequence of symbols or quantities. HMMs are used in ...
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### How does using DCT help in image compression

I once learnt that the Huffman Encoding is used to rid of redundant information, thus reducing file size. I am not sure how using a DCT, or FFT on an image can help in reducing file size. It does not ...
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I really having a hard time to tackle the following question. It is asked to load a ".mat" file using load file.mat. And the result is two variables: Fs varaible ...
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### Python implementation of multidimensional power spectral density with Welch method

I have done my best to write Welch method implementation for python for multidimensional time series and still in the case of one dimensional time series I am getting inconsistent response compared to ...
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### Getting low accuracy with deep convolutional NN trained on Imagenet 2011

I've downloaded the Imagenet2011 dataset and tried to train the Caffe imagenet network on it using the instructions here. I used about 500K images for training and 70K images for validation. I've ...
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### Rectangle detection in “real life” images

I have seen a lot of posts here and on SO and on various websites, using Matlab, OpenCV, name it, on how to detect rectangles in an image. I have done it myself too, using Matlab. My usual steps were: ...
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### Learning fundamentals of OFDM (Theory & Simulation)

Will you please suggest me some basic fundamental reference to learn OFDM techniques. I am looking for underneath theory with some basic mathematical explanations of CP, Subcarrier, FFT Size, Pilot ...
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### Wavelet Transform: Terms and Definitions

I have some doubts in respect to terms and definitions in the domain of wavelet transform/analysis. I analyse a signal by correlating each time my original time samples with different scaled and ...
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### Stopping Viola Jones Face Detection early

I want to try to improve an image processing technique for finding faces in images. I want to stop the Viola Jones face detector before it finds all faces, and do histogram equalization and other ...