[DRAFT] waveform type 'centroid' #7
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…al flatness to saturation
m0dB
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Oct 20, 2024
WIP PreRoll hack Matrix based on viewport and rect (#7) * bundle on macos * use Skin.WaveformDisplay for both decks * add shaders to mixxx target * call update from frameSwapped, test with only waveformrendererendoftrack * avoid error with colorChanged signals * fix typo in comment * example cleanup * keep track of size and viewport to update matrices in waveformwidgetrenderer * force continuous drawing of end of track, log framerate, use rgbamaterial instead of endoftrack material * use setViewport instead of resize, protect nullptr * call setViewport, setRect, setDevicePixelRatio * replace resize with setViewport, setRect, setDevicePixelRatio * set matrix with correct offset, minor fixes related with material changes --------- Co-authored-by: m0dB <m0dB@mixxx.org> move everything back to declarative style progress with marks
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I have been experimenting with a new waveform visualization that uses the spectral centroid https://en.wikipedia.org/wiki/Spectral_centroid , mapped to hue, and the spectral flatness https://en.wikipedia.org/wiki/Spectral_flatness , mapped to saturation.
The spectral centroid indicates where the center of mass of the spectrum is located, where 0 is in the low frequency band, 0.5 in the mid, and 1 in the high. Normally much more bands are used (typically an FFT) to calculate the spectral centroid. This implementation simply uses the information at hand: the filtered low,mid and high amplitudes (as mapped to R G B color components for the RGB waveform type).
By mapping the spectral centroid to hue, we get a color on a continuous color scale (red - yellow - green - cyan - blue).
Furthermore, I calculate the spectral flatness, which gives an indication of how "strong" the spectral centroid is. By inverse mapping the spectral flatness to saturation, the color is more pronounced for a strong spectral centroid, while it goes towards grey for a flatter spectrum.
Some comparisons between RGB (top) and Centroid (bottom). For example this kick-drum hi-hat sequence:
RGB:
Centroid:
RGB:
Centroid:
RGB:
Centroid:
