Tagged Questions

An octave is the interval between one musical pitch and another with half or double its frequency.

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1answer
27 views

Is there two Types of Scale Space in SURF algorithm?

I couldn't figure out below paragraph on SURF paper and hope that someone can help me to understand it. Bay H., Ess A., Tuytelaars T. Van Gool L. - Speed-Up Robust Features (SURF), page 4, ...
1
vote
2answers
87 views

Compensate for phase shift of Hilbert transform

I'm using Octave and trying to use the "instfreq" function from the time frequency toolbox which requires an analytic signal input. To get this analytic signal I'm using the Octave function "hilbert" ...
0
votes
2answers
126 views

OCR (optical character recognition) for Indian languages - segmentation

Can any one help me in how to extract a table from the whole document image and segment it? I have done segmentation for the document image which has only text by using the projection profile. So ...
0
votes
1answer
90 views

How to get spectrum of an image?

I have an image : img = imread('pic.jpg'); Now, How can I get spectrum of that image?
0
votes
1answer
218 views

Obtaining beat histogram using Tzanetakis algorithm

I am working to make a music player with automatic genre classification application in Java. On Google searches I mostly found the works of George Tzanetakis who describe an algorithm from Music Genre ...
0
votes
1answer
62 views

adjusting swept signal equation

When I do a spectrogram in matlab / octave I can create a swept signal that looks like the RED plot line below. But how can I create a swept signal like the BLUE line in the 1st plot using the ...
0
votes
1answer
254 views

Exponential decaying Swept / chirp signal [closed]

I'm trying to create a chirp/swept signal that has it's frequency going down exponentially using matlab/octave. I can't use the built in chirp function because I'm trying to create a chirp/swept ...
1
vote
2answers
236 views

Is imadjust a Matlab-only library? If so, can it be replaced?

I want to apply a homomorphic process to an image, and one of the steps involves the imadjust function. The source of this code is ...
2
votes
2answers
156 views

Equivalence of convolution through polynomial and matrix products

I am trying to understand the equivalence of convolution through polynomial (coefficient) multiplication, Fast Fourier Transforms, and matrix multiplication. I am using octave with the octave-signal ...
3
votes
2answers
169 views

What is an octave? It is said to be eight, but I cannot see the eight anywhere

When I searched for octave, I listened to the fact that if you take an octave band the lower cutoff is double the upper cutoff. Where is this name octave coming from, that is, where does the figure ...
1
vote
0answers
97 views

How to prevent Signal drifting when changing frequency

When I recreate a signal it seems to look great. But when I try and increase it's frequency (which is done in a for loop and the variable new_freq=2) it starts to drift. See Image below (The top ...
0
votes
1answer
144 views

FFT function isn't working on imported signals greater than a second

I have an fft function in matlab/octave that works great on an imported mono wav/audio signal that is 1 second long, but when the signal imported is more than 1 second the frequency values become ...
0
votes
0answers
286 views

Getting sound pressure level (SPL) for a frequency band from Welch's derived PSD

I'm using Welch's method (pwelch, in octave) to get the PSD of a recorded sound signal (i.e. pressure level vs. time). I then took the PSD data and took the sum of the amplitude in each octave band ...
-1
votes
1answer
260 views

Shifting / Permutation of an array taking a long time [closed]

I'm using matlab/octave and would like some help trying to improve the speed of my code. I've tried to vectorize the code but I run out of memory so I went back to for loops. What I'm trying to do ...
4
votes
3answers
357 views

creating a seamless signal / loop using interpolation

I'm trying to create a seamless loop using a "non-periodic" signal using interpolation to smooth out the beginning and the end but I'm still getting a click at the beginning when it loops and I listen ...
1
vote
3answers
829 views

Why is the gain of my IIR filter positive?

Sorry, two questions in one day! I'm struggling to understand what I'm doing wrong in this very simple filter design. I want to design a simple, single pole low pass filter and implement it as an IIR ...
0
votes
1answer
327 views

Frequency Response Error for IIR Butterworth in GNU Octave

I'm wondering why the following code for GNU Octave appears to be incorrect in the frequency domain by a magnitude of 2. For example, in Figure 1. (Sorry, I'm apparently not allowed to post images!) ...
0
votes
1answer
247 views

Spectrogram for created signal

I'm trying to test the specgram function located in the signal package in octave but I'm a little confused at the variables in specgram. What I would like to do is be able to get the specgram data ...
4
votes
1answer
294 views

Anti-aliased boolean masks for integration of CCD images

(This question was already asked on Stack Overflow under the tags Matlab/Octave/Signal-processing/Image-processing, but I am reposting it here following the advice of one user that this site may be a ...
4
votes
1answer
293 views

Why did my sine wave turn into a square wave when written to a WAV file in Octave?

I am trying to use Octave to generate a pure sine wave. The code for the same is as follows: x = 10.*sin(2*pi*(300/16000)*(0:1:400)); The sampling rate is ...