If you are looking for a specific or trying to identify which app generated this filename, it is common for brands like Vantrue, Viofo, or 70mai to use randomized alphanumeric strings for cloud-synced or protected clips.
The "useful feature" likely refers to one of the following common dashcam functionalities: C21VKWvLFvVAm2r5.mp4
Capturing synchronized footage from both the front and rear of the vehicle simultaneously. If you are looking for a specific or
The camera automatically saves and locks a video clip when it detects an impact or motion while the car is parked. C21VKWvLFvVAm2r5.mp4