Random Flashing with Infinite Color Engine RGBW

[HAWK77766]

The new Advanced RGB to RGBW Conversion with Temporal Dithering made near-black transitions a lot smoother. Thank you!

However, it introduced random color flashing for me—most noticeable with high-frequency changes and (seemingly) static near-black content, like game pause screens. This does not happen without this setting.

These flashes still happen even with very long smoothing, so it seems the flashing isn’t affected by smoothing.

I tested with different refresh rates, going from the previous 143 Hz all the way down to 59 Hz. I thought the new white channel would increase the bandwidth and lower the refresh rate, but the flickering still happens.

Hardware: SK6812 Cold White, 328 LEDs, multisegment, Pimoroni Plasma 2040
Pimoroni Plasma 2040 Firmware: HyperSerialPico v11.0.0
HyperHDR build action from 1st July

[awawa-dev]

Hi, do you have minimal backlight enabled? As noted in the wiki, enabling ICE RGBW reduces the available data bandwidth since it sends a full RGBW signal (4 channels instead of 3). Overall it may be quite subjective and depends on your LEDs, selected smoothing algo with its settings, refresh rate, and captured content. If this mode isn't working well for you, just disable it.

[HAWK77766]

I did some more testing:

• Minimal backlight is off, but trying it on made no difference.

• The issue persists across all smoothing algorithms and all their setting permutations. The same is true for the ICE RGBW settings.

• Even setting the smoothing time to an agonizingly slow 5000 ms does not prevent the flashing, which shouldn’t be possible. Therefore, I guess the problem is further down the pipeline - maybe even HyperSerialPico firmware or hardware.

• Lowering the refresh rate makes it worse! I tested going in steps down from 143 Hz to 30 Hz. This rules out bandwidth problems as the root of the issue, even with RGBW using 4 channels instead of 3.

• It seems like, near black, the color transition doesn’t work properly—or maybe the ICE RGBW dithering needs adjustment. Does it make sense to expose more settings for the user here?

Here is a video. Mind you: the flashing in the video is very subdued, and it’s much more noticeable in person.

Of course, disabling it would solve the issue, but the pumping effect is very noticeable in dark movie/game scenes. This forced me to lower the smoothing time to a minimum, where the pumping is less noticeable because it is shorter. ICE RGBW allows me to set the smoothing time much longer. Not being able to use it would be a great loss for my setup.

If you or someone else wants to look further into this, I will gladly provide additional information or feedback.

[awawa-dev]

Thanks for the detailed testing. Based on your observations, I don't think this is related to bandwidth.

ICE RGBW already implements two mechanisms to reduce near-black instability:

• Temporal dithering, which distributes RGB→RGBW conversion errors over time. However, it is primarily effective when color values change consistently in one direction. If the captured input oscillates back and forth around a threshold, the dithering cannot fully eliminate the resulting fluctuations.

• Input quantization, where RGB float values are only considered changed once they differ by at least 0.5 (instead of reacting to every tiny floating-point variation). This prevents constant toggling around quantization boundaries and significantly reduces near-black instability. However, if the input signal oscillates significantly, it cannot eliminate the resulting fluctuations completely.

You could also try increase the Smoothing factor (it acts as a low-pass filter) to attenuate input noise, or increase the Hybrid Spring Physics resistance/damping to make color transitions less sensitive to small input variations.

However, it introduced random color flashing for me

If it's only white LED flashing then you can try to disable it for testing (ICE white mixer threshold = 1.0)

[awawa-dev]

Minimal backlight is off, but trying it on made no difference.

Anyway it makes huge difference to turn it on to counter flickering in dark scenes unless you have 48bit capable LEDs such HD108...

[HAWK77766]

In my observations, there appears to be an W → RGB mixing issue near black.

When transitioning from bright to (near) black, there’s a very brief color-mixing mismatch. Imagine a transition that gets darker, but before the LEDs turn off, it flashes brighter green or blue, then turns off.

Minimal backlight: I tested only at the lowest possible setting, and the issue was still observable.

Setting the ICE white mixer threshold to 1.0 makes it less noticeable, but it’s still there.

Maybe I’m imagining it, but I notice it a lot more in HDR.

[HAWK77766]

Did some more testing, and the flashing is also visible without ICE RGBW, though a little less so.

I now suspect the HyperSerialPico v11.0.0 firmware.