Improve the display of dark videos

[dasl-]

We see issues on the pifi playing "dark" videos because the majority of pixels get turned off. For low brightness levels, the pixels dont have enough "steps" in the 0-255 brightness values to show the video.

One potential solution would be to have dynamic gamma calculations. If the frame is a "dark" frame, use a different gamma function that gives more dynamic range to the darker pixel values. This might be computationally expensive and difficult to tune.

Another option might be to re-write the LED driver libraries to give more dynamic range available in the brightness values. From: https://www.tindie.com/products/electromage/electromage-pixelblaze-v2-wifi-led-controller/

Pixelblaze was designed for APA102 LEDs (aka DotStar). These LEDs, and their cousin, the SK9822, are state-of-the-art and provide rock solid updates, faster refresh cycles, and the possibility of a dynamic range well beyond 0-255.

Pixelblaze has an HDR color mode for APA102 LEDs that can produce incredibly high dynamic range of intensities. This means patterns can still look beautiful at very low light settings, adds subtle tones between transitions, and can be driven with a range that is not possible on other LEDs and is not available in most LED driver libraries.

We use a python lib to drive the APA102 LEDs. I wonder if this means the LEDs are capable of more fine grained than 0-255 brightness?

Our APA102 lib we use has a global brightness setting, which we set to like 3 out of 31 by default. So i wonder if this gimps us even further, giving us an effective brightness of like ~one tenth of 255. So we are using only a tenth of an already handicapped dynamic range.

I think it is possible to get more granularity than 0-255 with APA102. See this blog post, and then this comment on the post: https://cpldcpu.wordpress.com/2014/08/27/apa102/#comment-749

More info: tinue/apa102-pi#44