elProducente.com provides useful information about digital video resolutions http://elproducente.com/native-real-vs-fake-4k-resolution-how-to-check/

“Most action cameras which offer native 4K at 30fps, also offer 1080p with 120 fps. Action cameras offering fake, interpolated 4K, mostly just offer 1080p with max. 60 fps. Therefore also check out the camera’s 1080p HD resolution.”

“4K resolution […at] 16:9 format (3840 x 2160 pixels) … if you multiply the pixels you’ll get a result of about 8.29 MP … if the sensor is smaller than 8MP, you can’t get a 4K video out of it … often cameras are advertised as 12 MP cameras, but the Megapixel just refer to the max. photo size”

“Cameras with larger sensors [than 12MP] will benefit from a higher photo resolution [not higher video resolution]”

“Even if the sensor offers more than 8MP it might not be capable of 4K resolution. Good example is the very common 16 MP Sony IMX206 sensor … looking at the data sheet of the sensor, you can see that 4K output is not listed.”