The filename indicates it is likely a video file recorded by a DVR or NVR security system (often associated with brands like Hikvision or Dahua ). Meaning of the Filename Parts:
: Lower resolution, designed for remote viewing on mobile devices or multi-screen grids to save bandwidth.
The primary feature of this file is that it is a of a security recording. Because it is a "Sub-stream" file, it will have a smaller file size and lower image quality compared to the primary recording, making it easier to share or upload.
: A unique identification number, often the serial number of the recorder or a specific event ID.
: Stands for Sub-stream . Security systems record in two modes: Main-stream : High resolution for playback and storage.
: Typically represents a system ID or a specific camera group code.