Issue with fragment Command When Init Segment is .m4s

[capuajuan]

Problem Description

I encountered an issue when using the fragment command with a DASH init segment that has the .m4s extension. Although DASH allows the init segment to be an .m4s file like the other segments, this init segment contains an ftyp box, meaning it behaves like an MP4 file.

Currently, the fragment command does not recognize this type of init segment as valid. However, adding .m4s to the list of allowed extensions resolves the issue.

Steps to Reproduce

1. Use the c2patool fragment command with an init segment in .m4s format that contains an ftyp box.
2. Observe that an error occurs, indicating the file is invalid.
3. Add .m4s to the list of allowed extensions.
4. Retry the command and confirm that it now processes correctly.