jm + time-series + phosphor   1

rendering pcm with simulated phosphor persistence
This is something readily applicable to display of sampled time-series metric data -- it really makes regular patterns visible (and is nicely retro to boot).
When PCM waveforms and similar function plots are displayed on screen, computational speed is often preferred over beauty and information content. For example, Audacity only draws the local maximum envelope amplitude and (what appears to be) RMS power when zoomed out, and when zoomed in, displays a very straightforward linear interpolation between samples.

Analogue oscilloscopes, on the other hand, do things differently. An electron beam scans a phosphor screen at a constant X velocity, lighting a dot everywhere it hits. The dot brightness is proportional to the time the electron beam was directed at it. Because the X speed of the beam is constant and the Y position is modulated by the waveform, brightness gives information about the local derivative of the function. Now how cool is that? It looks like an X-ray of the signal. We can see right away that the beep is roughly a square wave, because there's light on top and bottom of the oscillation envelope but mostly darkness in between. Minute changes in the harmonic content are also visible as interesting banding and ribbons.

(via an _amazing_ kragen post on ghetto electronics)
via:kragen  pcm  waveforms  oscilloscopes  analog  analogue  dataviz  time-series  waves  ui  phosphor  retro 
june 2013 by jm

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