The "atid" and ".mp4" components of your keyword point toward high-efficiency video containers used in modern portable systems. Portable video technology has evolved from simple playback devices to complex, multi-functional tools used in security, professional monitoring, and creative production.
Achieving "portable" status for high-volume video assets requires balancing three key factors: Compression Efficiency
E-book Reader: Text-based reading support (typically .txt files).
The Evolution of Portable Media: