_m_smp4 May 2026

Could you tell me or what software you were using when it appeared? This will help me give you a much more specific answer.

: Use a tool like MediaInfo or VLC Media Player to "Open" the file; these can often read the internal header to tell you the true codec, even if the file extension is non-standard. _m_smp4

: Files starting with an underscore or period are often treated as hidden or system-specific files. If you found this in a system folder, it is likely a pointer or index file for a video gallery. How to handle this file: Could you tell me or what software you