This is a Matroska Video container. It is a popular open-source format that can bundle an unlimited number of video, audio, and subtitle tracks into a single file.
MKV is the "nesting doll" of video formats (named after the Russian Matroska dolls). It is widely used for high-definition movies because it can hold multiple language tracks and subtitle files that you can toggle on or off. AgADuwcAAkEqWVY.mkv
In Telegram's API, strings starting with "AgAD" are often part of a file_id or file_unique_id . These are used by the platform to identify specific pieces of media across its servers. This is a Matroska Video container
Because this is a unique system-generated ID, there is no public "write-up" or general documentation for this specific file. However, It is widely used for high-definition movies because
Since this is a system-assigned name, the actual video content could be anything—a movie clip, a personal recording, or a meme shared in a group. About MKV Files
Unlike MP4 files, which can become corrupted if a recording is interrupted (like a computer crash), MKV files are designed to preserve the video even if the process stops abruptly.