signal-processing

问题 Here's some code I wrote to display the magnitude spectrum of an image: orig_imdata = imread('Original_Image.png'); spec_orig = fft2(double(orig_imdata)); spec_orig2 = abs(spec_orig); spec_img = fftshift(spec_orig2); imshow(spec_img); When I comment out the use of abs and just fftshift the image, I get an image, albeit with the phase and the magnitude. If I apply the abs function right after using fftshift , I get a blank result from imshow . I need an image of the magnitude of the spectral

问题 I'm planning to implement a "DSP-like" signal processor in Python. It should capture small fragments of audio via ALSA, process them, then play them back via ALSA. To get things started, I wrote the following (very simple) code. import alsaaudio inp = alsaaudio.PCM(alsaaudio.PCM_CAPTURE, alsaaudio.PCM_NORMAL) inp.setchannels(1) inp.setrate(96000) inp.setformat(alsaaudio.PCM_FORMAT_U32_LE) inp.setperiodsize(1920) outp = alsaaudio.PCM(alsaaudio.PCM_PLAYBACK, alsaaudio.PCM_NORMAL) outp

问题 I am trying to do a music identification application like shazam. This is an android app. First i have captured an audio signal through the MIC. Next I have implemented the hanning window function and FFT to the audio signal as shown as following code : private class RecordAudio extends AsyncTask<Void, double[], Void> { @Override protected Void doInBackground(Void... params) { started = true; try { DataOutputStream dos = new DataOutputStream( new BufferedOutputStream(new FileOutputStream(

问题 Sorry for question that may be trivial, but I am new in signal processing, and I didn't find python code with good explanation. So I will be glad to get explanation for dummy :) I have some signal that sampled each 1 nsec (1e-9 sec) and have, let say, 1e4 points. I need to filter high frequencies from this signal. Let say I need to filter frequencies higher than 10MHz. I want that for frequencies lower than cutoff frequency signal will be passed unchanged. It means gain of the filter will be

问题 Im searching for a way to convert Wave files into a list of numbers to cross-correlate the resulting vectors (like the numbers you get when you read a wave file on MATLAB) 0.6653 -0.8445 0.9589 -0.9999 0.9643 -0.8547 0.6797 -0.4525 0.1907 0.0858 -0.3557 0.5983 -0.7951 0.9309 -0.9953 0.9835 -0.8962 0.7402 -0.5275 0.2742 is there a way to do that in Android or even C/C++? i really dont know how to start. 回答1: WAVE file format is fairly simple, especially if you're interested in linear PCM

问题 I am doing an Windows application using C++. I have the next dude. I have this function where I receive a void * with data audio capture: void Pre_proc_mono::PreProcess(void *data, int lenbytes) { SLData_t *signal1; SLData_t *signal2; SLData_t *result; signal1 = (SLData_t*)data; signal2 = new SLData_t[lenbytes]; result = new SLData_t[2 * lenbytes - 1]; for (int i = 0; i < lenbytes; i++){ signal2[i] = signal1[i]; } } The loop always fail around 11000, why? What am I doing wrong ? The idea is

问题 I have a program doing a LOT of iteration (thousands to millions to hundreds of millions). It's starting to take quite a lot of time (few minutes, to a few days), and despite all my effort to optimize it, I'm still a bit stuck. Profile: using cProfile via console call ncalls tottime percall cumtime percall filename:lineno(function) 500/1 0.018 0.000 119.860 119.860 {built-in method builtins.exec} 1 0.006 0.006 119.860 119.860 Simulations_profiling.py:6(<module>) 6/3 0.802 0.134 108.302 36.101

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: How to Count the Number of Steps Using the Accelerometer Are there any well known algorithms to count steps based on the accelerometer? Hi i have developed android application. In one module I have to create a pedometer. Now at this stage I have to count the steps user walked by using accelormeter. I have search on internet and found different methods but none of that working. I have tried this Does anyone have

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 4 years ago . As part of a university project I have to do some signal processing and would like to output the results using the PC sound card. The software has to be written in C and needs to work with Windows (preferably 7 and XP). I have found code examples for outputting .wav and similar files, but I am interested in

问题 I've a Python code which performs FFT on a wav file and plot the amplitude vs time / amplitude vs freq graphs. I want to calculate dB from these graphs (they are long arrays). I do not want to calculate exact dBA, I just want to see a linear relationship after my calculations. I've dB meter, I will compare it. Here is my code: #!/usr/bin/env python # -*- coding: utf-8 -*- from __future__ import print_function import scipy.io.wavfile as wavfile import scipy import scipy.fftpack import numpy as