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:
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. 38499-70 701531471561_Sub_f_1532161730.mp4
: Often signifies the recording type, such as "File" or "Full" (continuous recording). The filename indicates it is likely a video
: A Unix Timestamp . This number represents the exact second the video was recorded. Converted Time: Saturday, July 21, 2018, 08:28:50 AM (UTC) . Key "Feature" : Often signifies the recording type, such as
: Lower resolution, designed for remote viewing on mobile devices or multi-screen grids to save bandwidth.
: Typically represents a system ID or a specific camera group code.