Most Chinese cameras use a HiSilicon 3518C SoC running Linux 2.6 (or 2.4, I cannot remember).
A year ago a reverse engineered the firmware of one of those cameras (it was not easy to persuade the seller in Alibaba to send it). With that, I built a compiler toolchain for the Hi3518C, re-generated the firmware and flashed it. There is a binary blob for the camera and it's not easy to replace it because it's not a UVC driver (it pre-dates UVC).
The plan was to get rid of the ActiveX and replace it with an HTML5 player and some other nifty stuff but then I got involved in another project and never finished that.