pub(crate) fn sniff_medium(head: &[u8], name: &str) -> Option<&'static str>Expand description
A video’s, a sound’s, a contact card’s or a calendar entry’s content
type by the file’s first bytes (head), never by its name: MP4, MOV and
3GP (ISO’s boxes, their brands), WebM, AMR, AAC, MP3, Ogg, WAV, vCard,
vCalendar and iCalendar. The name only tells an MP4 of sound from one of
video, which share their brands. None for anything else (a PDF named
.mp4 included).