Unknown manorial term

Whilst transcribing a perambulation of Old Sodbury in Gloucestershire from 1783, I came across two of the participants who were described as being ‘carnivals’.  They were listed with the steward, bailiffs, hayward and scavenger – manorial occupations of which I had heard.  But I have never seen the position of a carnival (or carnivall) before.

Does anyone know what a carnival did?