Bad colour banding in carplay

[alex124.rh]

Hi there

When using autobox, be that wired or wireless there is some pretty bad colour banding visible.

Rpi 5 8gb
Waveshare dsi-touch-c 8 inch
Hudiy 1.2

Any assistance appreciated. It’s a shame as it affects the good looking UI of carplay.

https://share.icloud.com/photos/04dyhbw ... XpAXOo54Vw

[hudiy]

Hello,
Please install grim (sudo apt install grim), make a screenshot (by executing grim command e. g. via SSH) and upload it here to the forum. Screenshots are stored in Pictures directory inside your home folder.

The issue is probably related to the display quality. Let's see if similar artifacts appear in the screenshot.

[alex124.rh]

will do, thanks

i don’t think it’s the screen in my opinion as it has a pretty high colour gamut, but we will see what the pics show. thanks for the input

[alex124.rh]

hi there,

https://share.icloud.com/photos/051BZN2 ... lVJtDjMLzg

here are the images from grim, they are present when viewed on my mac. so doesn’t seem to be the lcd display

[hudiy]

If the issue is also visible in screenshots, then you probably need to increase the video bitrate in the CarlinKit dongle settings. You can do this by going to http://192.168.43.1 after connecting to the dongle’s Wi-Fi network (Autobox-XXXX). In Video Settings, you'll find the Video Bit Rate option. Try setting it to 20 Mbps and see if the quality improves.

[alex124.rh]

Hi, can you see the screenshots? i’ll try that out thanks

[alex124.rh]

i’ve tried changing it but no luck it’s still horrifically bad. I never had this issue before, i think it might be since i updated to 1.2.

https://share.icloud.com/photos/02esSo9 ... zvLlFtSYHA

please see images

[hudiy]

Version 1.2 doesn't change anything about how CarPlay is displayed. In fact, CarPlay in Hudiy is just a video stream sent by the dongle. The CarPlay UI is rendered directly on the phone and then sent to the dongle as a video stream. It works similarly to remote desktop software (e.g., VNC).

If increasing the video bitrate on the dongle doesn't improve the quality, then perhaps the issue lies in the phone's rendering of the UI or in the way the phone encodes the video. You might want to check the Apple Community to see if anyone else has reported a similar issue on iOS 26. We managed to find a few threads that appear to describe problems with the phone's video encoding:

https://discussions.apple.com/thread/256162773
https://discussions.apple.com/thread/256149382

[alex124.rh]

Hi I understand this however the issues weren’t there on ios 26 with Hudiy 1.0

I may recall something about hudiy 1.2 having improved carplay and stuff?

“We’ve made a number of improvements to display handling.
Thanks to the updates in Raspberry Pi OS Bookworm and labwc, Hudiy can now run fully on Wayland without the X11 compatibility layer.
This enhances rendering performance for the native UI, Android Auto and CarPlay. Full Wayland support mode is now the default.”

Maybe this is of relevance

thanks again

[hudiy]

Hi I understand this however the issues weren’t there on ios 26 with Hudiy 1.0

I may recall something about hudiy 1.2 having improved carplay and stuff?

“We’ve made a number of improvements to display handling.
Thanks to the updates in Raspberry Pi OS Bookworm and labwc, Hudiy can now run fully on Wayland without the X11 compatibility layer.
This enhances rendering performance for the native UI, Android Auto and CarPlay. Full Wayland support mode is now the default.”

Maybe this is of relevance

thanks again

These changes were related to the transport of video frames between the projection endpoints (CarPlay, Android Auto) and the Raspberry Pi's GPU. Version 1.2 uses zero-copy mechanisms between the decoders and the Raspberry Pi GPU. These improvements only affect the smoothness of frame delivery (because the transport is much faster), while the actual frame rendering mechanism remains the same (OpenGL).

Edit:
Looks like CarPlay uses 8-bits for video stream encoding. The difference between 8 and 10 bits encoding is explained by this picture:

810bit.png (57.57 KiB) Viewed 1237 times

The "liquid glass" introduces more gradients and because of 8-bit encoding, some colors may appear with lower quality.