You believe this is easy when the device has multiple recording sensors and multidimensional information (such as spatial information, changes in focus sensors durning recording, etc) is part of recording that is digitally signed?
The key idea is to leverage the array of sensors built into modern smartphones and tablets - accelerometer, gyroscope, GPS, WiFi/cellular signal data, etc. - to cryptographically sign the sensor readings along with the visual data itself at the time of capture. This extra layer of verifiable sensor data would help establish that a recording originated from a real physical device in a particular place and time, as opposed to a purely digital fabrication.
Historically, technologies like digital signatures and public key cryptography started out in niche military/government applications before becoming ubiquitous in the computer era. In a similar way, sensor-level authentication of audiovisual media could follow an adoption curve driven by the growing need to combat sophisticated AI forgeries.