The suffix _source indicates this is the original, high-quality master file from which other versions (derivatives or transcodes) are created.
Usually H.264 (AVC) or H.265 (HEVC), which are standard for high-definition master files. 0h516tkgehpt0uug36ouy_source.mp4
Systems like the Internet Archive use _source.mp4 files to generate multiple web-friendly versions: Files, Formats, and Derivatives – file definitions The suffix _source indicates this is the original,
The .mp4 extension signifies an MPEG-4 Part 14 container, a standard for storing video, audio, and metadata. 2. Structural Components of an MP4 Container a standard for storing video
The string 0h516tkgehpt0uug36ouy is likely a hash or a base32/base64 encoded unique ID used to prevent filename collisions in large databases.
The subject 0h516tkgehpt0uug36ouy_source.mp4 appears to be a system-generated filename for a digital video file, typically found in automated media workflows or archival systems.