Questions tagged [numpy]

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fft formula convention

I try to code up an algorithm from a scientific paper where they solve a differential equation using Fourier transforms. In the paper, they use the FT convention $\rho(x_i) = \sum_{k=-m}^m r_k e^{i2\...
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0answers
71 views

How to get an interpolation weight from a mathematical definition

It was recently explained to me that a "Nearest neighbor" kernel for 1D interpolation can be implemented like this using NumPy ...
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0answers
55 views

Why are low frequency peaks not sharp in scipy fft?

I am using numpy/scipy to plot graphs of sine waves. frequencies at 15 Hz or higher give nice, sharp peaks, but at lower frequencies, the peaks are smeared and the actual peak frequency can't be seen ...
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0answers
982 views

Acceleration time series to velocity conversion using DFTs

I have 1000 Hz time series data for acceleration (512 data points), which I want to convert to velocity. I am trying to use the omega arithmetic method to achieve this. Following are the steps I am ...
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0answers
10 views

How to save MFCC features and frame energy of several wav files to one .npz file for machine learning training?

I am creating a English-Italian corpus of around 100 hours of English audio from LibriVox aligned with their Italian textual translation. The alignment is at a sentence level and the corpus consist of ...
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0answers
30 views

Why is there a difference in the spectrum of an audio file between Sonic Visualizer and my Python script?

I am working on a script which is creating a spectrum analysis from an audio file using SciPy and NumPy. Before I started, I analyzed the file using Sonic Visualizer, which got me the following result:...
0
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1answer
59 views

Analyze PCM data

I am getting some 16 bit PCM data (raw bits) from a serial port . I need to collect this stream of bits using some python application running in PC and store it somewhere(Assume it in an array). I ...
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1answer
30 views

Output shape of numpy's rfft function

For numpy's rfft function, the length of the output is about half of N, the length of the input sequence. What is the reason behind this? What are the frequency bins?
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0answers
45 views

Understanding outputs of image Fourier Transform in Numpy

I am trying to understand the meaning of FFT outputs with respect to images. Take a look at the following example: ...
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0answers
30 views

delayed result in sinc upsampled signal

I have implemented an infinite kernel sinc interpolation. For some signals I notice an artifact, visible at the right end of the plot. I am wondering: is it a bug in my code or a phenomenon usual for ...
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0answers
165 views

Is there any python code for applying a-law/mu-law on 3D numpy array?

I have 3D numpy array of probabilities between [0,1], I need to emphasize on some area with lower probabilities. I was suggested to apply a-law and mu-law. I am wondering if there is python library/...
0
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1answer
130 views

Choppy output when trying play through a callback buffer

I am trying to make a keyboard in python where every note's frequency is a ratio of the previous note but my output is strangely choppy for some reason. Here's an example of what I mean. I'm using ...
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2answers
190 views

Shifting signal smaller than discrete step

I have a image that I need to shift with less than a pixel. My plan was to do a Fourier transform and multiply the signal with $e^{-aiu-biv}$ where $a, b$ are the shifts in x and y direction. This ...
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0answers
5k views

AM Modulator Demodulator in Python

I am trying to make a AM modem using Python Numpy and Matplotlib. I am successful in generating the AM Signal but I cannot demodulate it using a lowpass filter function that I made. The demodulation ...
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2answers
8k views

Avoiding “RuntimeWarning: invalid value encountered in log10” when converting FFT data to dBFS

I've attached some code below that I'm having some issues with. Basically, I need to write a function to get the dBFS value of a signal at a specified Hz value, at a given channel in a .wav file. ...