It does not correspond to any standard audio/video format, though the "mp4" suffix suggests it might be intended as a video file (e.g., filename.dsmowmp4 ).
If you encountered this term in a specific file or system, please consider checking the following: DSmowmp4
If you can provide the where you saw "DSmowmp4"—such as a file extension , a string within a program , or a web search —I can better investigate what it might be. It does not correspond to any standard audio/video