If you've been following my blogs, you know this journey started with a simple question: why does my infotainment look so generic? That was the Golf GTE era. Back then, I thought swapping a few images would be the end of it. Spoiler alert: it wasn't. Years later, I'm still here, hex editor in hand, reverse-engineering binary formats and building tools to make this hobby accessible to everyone.
This time I am writing about GCA files (the Generic Car Adjuster configuration files) and they're the silent architects of your infotainment's button layouts, touch zones, and lighting behavior. And here's where it gets interesting: you can modify them to add custom ambient lighting zones.
I wrote about this in the past:
— Additional Ambient lighting zones (and controls)
— Investigating VW Ambient zones: A full visual overview of the zones (MIB2H firmware 1427)
— Investigating SEAT Ambient zones: A full visual overview of the zones (MIB2H firmware 1447)
Investigating Skoda Ambient zones: A full visual overview of the zones (MIB25H firmware 1440)
What Even Is GCA?
Think of GCA files as the instruction manual for your infotainment's UI skin. They tell the system:
— Where buttons are physically located on the screen
— What images to display for each button state
— Which features (like ambient lighting zones) are available
— How to respond to user input
— For ambient lighting setups specifically, the GCA file defines the zones: the areas of your interior that can light up. Want more zones than Volkswagen gave you? Want zones in different positions? This is where GCA editing comes in.
Normally, people would share .gca files around, that would enable additional zones, but why not have the full controls at your fingertips? In the past I used to write Python scripts and 010 Editor templates, that would help you with understanding and unpacking the format. but that would take a lot of knowledge and additional tools to start editing things by yourself. To make things easier for the community, I made mqbtools.nl a few years ago, for easier customization of your car.
So now I made a web-based GCA editor that runs entirely in your browser. No installation. No command-line nonsense. Just upload your GCA file (which you got by dumping files from the MIB, or getting it from the firmware files), edit it, download the modified version, upload back to your car: enjoy the changes.
What can it do?
— Viewing and editing ambient zone layouts
— Dragging zones to new positions
— Adding/removing zones
— MIB3 and MIB2 file support
— Real-time canvas preview showing button and image locations
— Use your own custom background in the plot, to aid your editing efforts
What it cannot do:
— Add new features. This is pretty car specific… especially with MIB3 car setup screens, which are quite complex and linked to other files like the car_lhd/car_rhd.mcf animations.
— Install the new files back on your car. Find a way to do this yourself. I can't supply service and support to anyone out there… I just give you the saw, but I will not teach you how to build a house with it.
— MIB3GP GCA files. that's a work in progress
Enjoy playing around with this tool! You can find it at mqbtools.nl/gca/
Some screenshots:
Go to mqbtools.nl/gca/ to try it out!
Comments 5
Long time ago I've moved "center console" control using your old topic and it worked fine, but after MIB update I could not be bothered to refresh my memory of how it was done. Pretty niche tool, but very helpful. Thank you!
One question — is it possible to add new images? In your old posts you've tested lot of "hidden" images, but my car have only three — doors, footwells and center console. It would be great if it was possible to add e.g. door card pockets image when missing. In the past I've added it to door ambient image. It worked, but seemed a bit "hacky" way to achieve the result
Yes, you can add additional zones :-)
The GCA files for the MQB Evo seem to be a lot cleaner than the old MQB ones. No more leftovers with 8 zones and such!
Amazing )
As usually — an exceptional work done. Good job man!
Thank you! I really hope people can put this tool to good use and start retrofitting ambient LEDs to this platform :-)