A simple FFT-based tuner and spectogram.
Rambajz needs SDL2, SDL2_ttf and JACK development files to compile.
To build Rambajz, simply run make. It is possible to customise the default
build flags either by passing them as a command line argument to make (e.g.,
make C=clang), or by putting them in Makefile.local.
Before running Rambajz, ensure the JACK audio server is active. To run Rambajz,
run build/rambajz from the project root.
By default, Rambajz tries to connect to all physical input ports (more
specifically, all JACK ports matching the regex system:capture.*). You can
pass an alternative regex as the first argument to build/rambajz.
The top of the application window contains a tuning bar showing the detected dominant frequency (on the right) and the tone corresponding to it (on the left), along with its deviation from the standard tuning in cents.
The rest of the application window displays a spectogram of the recorded data. The vertical red line marks the found dominant frequency. The spectogram shows the frequency response in the range (20 Hz, [jack sample rate] / 2). It uses a logarithmical scale, meaning for example that every two notes separated by an octave are the same distance apart.
Simple movement and zooming of the spectogram's viewport is supported: either use the touchpad, or J/K to zoom in/out and H/L to move left/right. The dominant frequency is only calculated from the current viewport.
The spectral analysis is done using a simple implementation of FFT which runs in O(N log N). A custom mode in which the Fourier transform is done in a naive way separately for each frequency of interest is also available. Pressing D toggles between the two modes. The advantage of the latter mode is that while the FFT samples the same set of frequency bins for each frame regardless of the viewport, in the custom mode the frequencies of interest are chosen so that they span the current viewport equally (as seen by the user -- i. e. accounting for the logarithmic scale).
To exit the application, press Q, Escape, or close the window.