A file with a similar naming convention (e.g., btran256 ) was referenced in a Bento4 GitHub issue regarding Dolby Vision encryption and "bad payload data" in the mdat box [1].
If you are not referring to the scientific video, you might be looking for information on one of the following: b234.mp4
The file is associated with Global Unique Identifier (GUID) 99E9BB74-F2A1-4CEE-B234-5D4D3A3A3A10 . A file with a similar naming convention (e