I suspect we'll need to return to the idea of getting our news from trusted sources, rather than being able to rely on videos on social media being trustworthy.

Technically, we could try and build a trusted computing-like system to ensure trust from the sensor all the way to a signed video file output, but keeping that perfectly secure is likely to be virtually impossible except in narrow situations, such as CCTV installations. I believe Apple may be attempting to do things like this with how Face ID is implemented on iPhone, but I suspect we'll always find ways to trick any such device.