fft

问题 I have to use FFT to analyse the frequency of an audio file. But I don't know what the input and output is. Do I have to use 1-dimension, 2-dimension or 3-dimension array if I want to draw the spectrum's audio file? And can someone suggest me library for FFT on J2ME? 回答1: @thongcaoloi, The simple answer regarding the dimensionality of your input data is: you need 1D data. Now I'll explain what that means. Because you want to analyze audio data, your input to the discrete Fourier transform

问题 I have to use FFT to analyse the frequency of an audio file. But I don't know what the input and output is. Do I have to use 1-dimension, 2-dimension or 3-dimension array if I want to draw the spectrum's audio file? And can someone suggest me library for FFT on J2ME? 回答1: @thongcaoloi, The simple answer regarding the dimensionality of your input data is: you need 1D data. Now I'll explain what that means. Because you want to analyze audio data, your input to the discrete Fourier transform

问题 I am trying to perform FFT on an audio file to find frequency using the Accelerate framework. I have adapted code (probably wrong) from this question: Spectrogram from AVAudioPCMBuffer using Accelerate framework in Swift Although, the magnitudes from ' spectrum ' are either ' 0 ', ' inf ' or ' nan ', and the ' real ' and ' imag ' components of the complex split print similar results; indicating that this is the cause of the problem as: ' magnitude = sqrt(pow( real ,2)+pow( imag ,2) '. Correct

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 6 days ago . I am looking for a library that can accept a chunk of audio data and return the average amplitude over time within a given frequency band. I've already asked this question over at comp.dsp, but it's clear to me that acquiring the know-how to build this on my own using a basic FFT library is going to require more

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 6 years ago . I have a ascii file containing 2048 x and y value pairs. I just want to know how to plot fft of y in MATLAB. I am writing following MATLAB code but could not be able to find appropriate result. How can I do this? This is what I have tried: I = load('data1.asc'); for i = 1:2048 y = I(:,2); end plot(x) Fs = 40000;

问题 Hi guy's I'm working on simple signals and I want to calculate the Fourier transform of a signal, get the magnitude and phases, then reconstruct the original signal from that. I'm basing my code on this thread. Code: >> n=0:99; >> N=length(n); >> x = sin((2*pi/N).*n).*cos((pi/N).*n); >> F = fft(x); >> mag = sqrt(real(F).^2 + imag(F).^2); >> phase = atan2(imag(F),real(F)); >> re = mag .* cos(phase); >> im = mag .* sin(phase); >> F_i = re + 1i*im; >> x_i = ifft(F_i); >> figure;stem(x);figure

问题 Blow is a main file PROGRAM SPHEROID USE nrtype USE SUB_INFO INCLUDE "/usr/local/include/fftw3.f" INTEGER(I8B) :: plan_forward, plan_backward INTEGER(I4B) :: i, t, int_N REAL(DP) :: cth_i, sth_i, real_i, perturbation REAL(DP) :: PolarEffect, dummy, x1, x2, x3 REAL(DP), DIMENSION(4096) :: dummy1, dummy2, gam, th, ph REAL(DP), DIMENSION(4096) :: k1, k2, k3, k4, l1, l2, l3, l4, f_in COMPLEX(DPC), DIMENSION(2049) :: output1, output2, f_out CHARACTER(1024) :: baseOutputFilename CHARACTER(1024) ::

问题 Dear stackoverflow community! Today I found that on a high-end cluster architecture, an elementwise multiplication of 2 cubes with dimensions 1921 x 512 x 512 takes ~ 27 s. This is much too long since I have to perform such computations at least 256 times for an azimuthal averaging of a power spectrum in the current implementation. I found that the slow performance was mainly due to different stride structures (C in one case and FORTRAN in the other). One of the two arrays was a newly

问题 I am new to FFTs so I am slightly confused on some concepts. So far the FFT examples I've seen for equation multiplication involve equations with consecutive exponents (i.e. A(x) = 1 + 3x + 5x^2 +... and B(x) = 4 + 6x + 9x^2 + ... and C(x) = A(x)*B(x) ). However, it is possible to use FFT on two equations that do not have equal exponents? For example, is it possible to use FFT to multiply: A(x) = 1 + 3x^2 + 9x^8 and B(x) = 5x + 6 x^3 + 10x^8 in O(nlogn) time? If not, are there any cases where

问题 I want to use Fast Fourier Transform but already trying a simple back and forth transformation doesn't work. The code is import cv2 import numpy as np img = cv2.imread('Picture.bmp',0) f = np.fft.fft2(img) fshift = np.fft.fftshift(f) f_ishift = np.fft.ifftshift(fshift) img_back = cv2.idft(f_ishift) img_back = cv2.magnitude(img_back[:,:,0],img_back[:,:,1]) and the error is Traceback (most recent call last): File "test.py", line 8, in <module> img_back = cv2.idft(f_ishift) TypeError: src data