How does Volumio know the duration of a song?

I’m analysing a Volumio playlist and comparing it to an M3U playlist file that I have. In the M3U file each song’s duration in seconds is specified after the #EXTINF tag.

However, in a Volumio playlist file I only see the uri (location), display title, artist name, album name and album art location. I don’t see a duration field.

Does this mean that I can ignore the duration from M3U playlists when trying to convert from M3U to Volumio format? If so, how does Volumio get the song’s duration?