Function smil 

fn smil(parts: &[(Kind, String)], words: bool) -> String

The message’s SMIL, as AOSP Messaging lays one out: the pictures and videos above (four fifths of the height when there are words), the words below, one <par> each, the words last. A video or a sound plays its own length (no duration said: Sioul does not read it, and a wrong one would cut it short on a phone that follows the SMIL).