"b_111.mp4" does not appear to be a widely known viral video, specific movie file, or established internet mystery. In technical contexts, a filename like this is typically a generic system-generated name for a video file.
: Use a tool like ffmpeg to non-destructively add author or description tags directly into the file's "atoms" (data boxes). b_111.mp4
To understand what "b_111.mp4" actually contains without watching it, you can extract its technical summary (metadata). Tools like mp4info can provide a textual report including: "b_111