livefft

Real-time spectrum analyser in Python

Introduction

A basic spectrum analyser which reads data from the sound card and displays the time history and spectrum in real time.

Installation

Ubuntu 16.04 LTS

Using the system Python 2, install dependencies using apt:

sudo apt install python-pyqtgraph python-pyaudio

Clone & run livefft:

git clone https://github.com/ricklupton/livefft
python livefft/livefft.py

Anaconda

Using the Anaconda python distribution, create a new conda environment with the required pacakges and activate it:

conda create -n livefft -f requirements.txt
source activate livefft

Clone & run livefft:

git clone https://github.com/ricklupton/livefft
python livefft/livefft.py

Usage

The time signal is shown in the top plot, the spectrum below.

Adjusting plots

Adjust the zoom of plots using the mouse wheel over the axes, or by dragging with the right mouse button. Pan using the middle mouse button.

Tip: To zoom the frequency axis without losing the origin, place the mouse over 0 then spin the mouse wheel.

See the pyqtgraph documentation for more details.

Sampling time

Change the length of the sampling buffer with the + and - keys. Using a longer buffer can be useful to make the spectrum respond more slowly, or for looking at low frequencies. Using a shorter buffer makes the spectrum respond more quickly.

Other keyboard shortcuts

• SPACE: pause
• L: toggle log/linear scale
• D: toggle downsampling (for faster graph updates)