A Rogation Days processional hymn: Ardua spes mundi (Ratpert († c.890))

Described at the YouTube page as a versus ad processionem in diebus dominicis ("hymn for Sunday processions"), Ardua spes mundi was apparently sung at Rogation Day processions, according to David Hiley's Western Plainchant. (The Rogation Days are the three weekdays prior to Ascension Day; we're in the middle of them now.)

Here is a recording of the hymn, sung by "Ensemble Gilles Binchois
Dominique Vellard, direction, en collaboration avec Wulf Arlt":



In a section on "Processional Hymns" (note that "versus" is another word for "hymn"), Hiley says:

Ratpert's Ardua spes mundi may serve as an example of the St. Gall versus....In the Rouen Cathedral manuscript (Paris, Bibliotheque Nationale, lat. 904, thirteenth century), from which [the illustration] is transcribed, both Ardua spes and Humili prece are sung in the procession before Mass on the Rogation Days leading up to Ascension Day (the weekdays following the fifth Sunday after Easter). In both chants, verses in honor of Rouen saints are added to those already present; Ardua spes invokes Romanus and Audoenus.  The same melody is used for the refrain and the strophes (some other processional hymns have two different melodies).

Other examples of "processional hymns" cited by Hiley are the more well-known Pange lingua and Crux fideles.  "Ratpert," who wrote this text, was a monk of St. Gall and a composer of liturgical poetry;  according to BrillOnline, Ratpert:

(after 850 – before 912), was educated at Saint Gall Abbey and lived there as monk and teacher until his death. In the Middle Ages he was known as the author of liturgical poems in Latin, especially an All Saints Day litany. His Old High German Galluslied now survives only in the Latin retro-translation by Ekkehard IV. His Casus sancti Galli form the prelude to the Saint Gall house chronicle that was continued up to the 13th century.

The image in the YouTube video is from the St. Gall manuscript; below  are screenshots from that same manuscript of all four pages (!) of this hymn.  I do not at the moment have an English translation, but will return if I find one (or can work it out myself!).    Spes mundi is "hope of the world" - and Google Translate says that Ardua spes mundi translates as "towering hope of the world":