Most standard media players cannot play a standalone M4S file because it lacks critical "initialization" data. However, some specialized tools can handle them:
An is a segmented video fragment typically used in MPEG-DASH (Dynamic Adaptive Streaming over HTTP) to deliver high-quality media over the internet. These files are not complete movies but rather 10-second "chunks" of a larger video stream. open .m4s file
It does include the initial ftyp or the full moov (those are in the initialization segment, often .mp4 or .m4i ). Most standard media players cannot play a standalone