Dithering vs maxing out framerate about ledscape

[Yona-Appletree]

Mattias,

Let's consider interpolation and dithering separately, and I do
apologize if I'm telling you things you already know (or if I'm making
any factual errors or false assumptions).

Interpolation happens first and handles cases where the incoming
framerate is low, but the outgoing framerate is high. This can be useful
to save resources on the effect generation side. In your case, the
difference between input framerate (240) and output (300) is low, so I
would agree and say you don't need interpolation. You might consider
using it though, if your visualization generation uses more CPU than
LEDscape does to do interpolation.

Dithering handles the fact that WS2811-based LEDs have a linear
brightness response but human perception is more logarithmic. The
perceived brightness delta between brightness levels 0, 1, 2, etc... is
much greater than the difference between 250, 251, 252. Inspired by
FadeCandy, dithering will improve the perceived brightness shift by
"flickering" the LED levels over time so they average to a value between
the levels that the hardware supports. Generally, I would say that
dithering helps at any framerate above 200fps, but I would experiment
with it to see. You'll see the most improvement when the brightness
levels are low...you can try dimming your pattern generation down to 10%
or so.

Let me know what you find out, and we can update the README and close
this ticket.

Thanks,

Yona

MFornander mailto:[email protected]
July 28, 2014 at 14:23

Yona,

Apologies if I am abusing the "Issues" as a forum. I'm wondering if
your would recommend leaving dithering on or off in the following
scenario:

We produce and consume OPC frames on the same BBB and simply loop back
the UDP messages on localhost. This allows us to use the OGL OPC
simulator to test patterns for people without hardware. Since our
strands are 100LEDs we have a max rate of 300fps. We are close to this
with a rate of around 240FPS both producing OPC frames and consuming
them using opc-server.

I'm turning dithering and interpolation off at these rates since our
effects are time-driven functions that are driven by delta-T, not
frame index. At these rates I think it's the right thing do do but I'd
like your opinion in the matter.

Cheers,
Mattias

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Yona Appletree
Senior Developer
Concentric Sky, inc
[email protected]