Sample held in a buffer from DirectX. It's a sample of a note played and captured from an instrument. How do I analyse the frequency of the sample (like a guitar tuner does). I believe FFT's are involved, but I have no pointers to HOWTO's. ...
Have done fft (see earlier posting if you are interested!) and got a result, which helps me. Would like to analyse the noisiness / spikiness of an array (actually a vb.nre collection of single). Um, how to explain ... When signal is good, fft power results is 512 data points (frequency buckets) with low values in all but maybe 2 or 3 ar...
Where can I find a free, very quick, and reliable implementation of FFT in C#? Can be used in a product? or are there any restrictions? ...
We're trying to analyse flow around circular cylinder and we have a set of Cp values that we got from wind tunnel experiment. Initially, we started off with a sample frequency of 20 Hz and tried to find the frequency of vortex shedding using FFT in matlab. We got a frequency of around 7 Hz. Next, we did the same experiment, but the only ...
I've been looking everywhere for a sample Fast Fourier Transform implementation/tutorial in (preferably) C#. However, every one I've found has been poor at explaining what's going on, and/or poorly commented; or they assume that you already know the FFT algorithm, or they're tutorials about how to USE FFTs. Anyone know of a good sample...
1) Besides the negative frequencies, which is the minimum frequency provided by the FFT function? Is it zero? 2) If it is zero how do we plot zero on a logarithmic scale? 3) The result is always symmetrical? Or it just appears to be symmetrical? 4) If I use abs(fft(y)) to compare 2 signals, may I lose some accuracy? ...
I want to know how to perform "spectral change detection" for the classification of vocal & non-vocal segments of a song. We need to find the spectral changes from a spectrogram. Any elaborate information about this, particularly involving MATLAB? ...
Hi, I'm working on a polyphonic music transcription project. I have read some papers and gone through articles which explains similar tasks. I'am very confused about many aspects of the problem domain. Hope someone will be able to help me. So far I have obtained a stream of decoded audio data from a given mp3. I have understood onse...
I am trying to create a graphical spectrum analyzer in python. I am currently reading 1024 bytes of a 16 bit dual channel 44,100 Hz sample rate audio stream and averaging the amplitude of the 2 channels together. So now I have an array of 256 signed shorts. I now want to preform a fft on that array, using a module like numpy, and use ...
Hi guys, i just don't understand how to perform a FFT on two polynomials such as X^2+1 and X+1...can anyone step by step go through the process with me? Thanks very much ...
The typical FFT for audio looks pretty similar to this, with most of the action happening on the far left side http://www.flight404.com/blog/images/fft.jpg He multiplied it by a partial sine wave to get it to the bottom, but the article isn't too specific on this part of it. It also seems like a "good enough" modification of the datase...
Is it possible with FFT to find an occurrence of a small wav sample inside of a longer wav, if it is known that that exact sample exists somewhere in the wav (but may be mixed with other sounds)? edit (after receiving two responses): What if I have a library of all known sounds that can be in the larger WAV and wish to find occurrences...
For a FFT function I need to permutate or shuffle the elements within an array in a bit-reversed way. That's a common task with FFTs because most power of two sized FFT functions either expect or return their data in a bit-reversed way. E.g. assume that the array has 256 elements I'd like to swap each element with it's bit-reversed patt...
Hello, Audio processing is pretty new for me. And currently using Python Numpy for processing wave files. After calculating FFT matrix I am getting noisy power values for non-existent frequencies. I am interested in visualizing the data and accuracy is not a high priority. Is there a safe way to calculate the clipping value to remove th...
I'm wondering if anyone knows of a fast (i.e. O(N log(N)) ) method of calculating the average square difference function (ASDF) or average magnitude difference function (AMDF) for a periodic signal, or it is even possible. I know that one can use the FFT to calculate the periodic cross correlation. For example, in Matlab code, for i=1:...
Is there a FFT-based 2D cross-correlation or convolution function built into scipy (or another popular library)? There are functions like these: scipy.signal.correlate2d - "the direct method implemented by convolveND will be slow for large data" scipy.ndimage.correlate - "The array is correlated with the given kernel using exact calcu...
Hi. I have an assignment about fftw and I was trying to write a small program to create an fft of an image. I am using CImg to read and write images. But all I get is a dark image with a single white dot :( I'm most likely doing this the wrong way and I would appreciate if someone could explain how this should be done. I don't need the ...
Wikipedia's Wavelet article contains this text: The discrete wavelet transform is also less computationally complex, taking O(N) time as compared to O(N log N) for the fast Fourier transform. This computational advantage is not inherent to the transform, but reflects the choice of a logarithmic division of frequency, in contrast to t...
Taking speed as an issue it may be better to choose another language, but, what is your library/module/implementation of choice for doing 1D FFT in python? ...
i am going through the above topic from CLRS(CORMEN) (page 834) and I got stuck at this point. Can anybody please explain how the following expression, A(x)=A^{[0]}(x^2) +xA^{[1]}(x^2) follows from, n-1 ` Σ a_j x^j j=0 Where, A^{[0]} = a_0 + a_2x + a_4a^x ... a_{n-2}x^{\frac{n}{2-1}} A^{[1]} = a_1 + a_3x + ...