Comment by librick

*Jankiness, not jerkiness. I could have clarified that better; what I mean is that it was strange to me that the backup camera had two stages. The camera video feed comes up first, then the yellow overlay lines are rendered on top later. Which makes sense, that way the user doesn't have to wait for Android to boot up completely before they can view the backup camera.

I want to look more into rear camera viewing/recording too. The binary /sbin/earlyrvc in the repo (in the boot recovery image directory) is what displays the camera on boot. After that there's a few Honda-specific APKs that handle backup camera access for the rest of Android. I had some luck using Ghidra for static analysis of /sbin/earlyrvc. But the biggest hurdle I ran into is a lack of documentation on NVIDIA kernel drivers and the graphics pipeline.

As for rooting, I used a paid ($25) service. You sign up on this sketchy site, pay the $25 to get a unique code (a UUID), and then visit a specific website from the headunit's web browser. AFAIK, whoever runs that service is basically just using a WebKit exploit chained to some other Android exploit(s) to achieve root. It worked for me. I've added some more info on this to the README. But one of my goals is to make rooting easier/free/open source to lower the barrier-to-entry for headunit hacking. It'd be great to see a PR for that