In reading a medieval text, it's helpful to know that the medieval scribe did not distinguish between I and J as separate sounds, and likewise between U and V. J was simply considered an alternate way of writing I, and U as an alternate way of writing V. V or v tended to be used at the beginning of the word and u in the middle. J was slower to catch on, most often as the final in the final stroke in a series of roman numerals, and more occasionally as an initial or terminal letter. Systematic use of U and V to represent different sounds began in Italy in the 16th c., and became general in England around 1630, about the time J came into general use as in English as a separate letter.
So in a medieval text, we would frequently see even as euen, unto as vnto, and just as iust.
When we read that Gawain, preparing to meet the Green Knight, had a helm equiped
Wyth a lyyghtly vrysoun ouer the auentayle,
Enbrawden and bounden wyth the best gemmez
how are we to pronounce "vrysoun"? We could look at alternate spellings of the word in other works, but as far as I know this is the only place it appears. Some other versions of the text transcribe it as "urisoun"
I read it as "urisoun", because it scans and illiterates better. It may be related to the later term Orris, which the OED describes as lace, embroidery or hangings worked with gold.