The protagonist of Hamlet by William Shakespeare is Hamlet, and when we meet him we know immediately that he is distraught. We learn that his father, the former king, has been murdered and his mother has remarried within a few short months--to his father's brother.
Hamlet is quite a sensitive character in many ways, and he is not only rightly upset at his mother's "o'erhasty" marriage but he also has suspicions that his uncle is the one who is responsible for the old king's death. Everyone else seems to think this new match is a fine idea, but Hamlet most certainly does not.
The scene to which I assume you are referring is found in Act I scene iv. Hamlet has been notified by his friends that his father's ghost seems to be appearing in hopes of communicating with Hamlet, so it is midnight and Hamlet is with Horatio and two others on guard duty, waiting for the Ghost to appear. Earlier in the day, Claudius and Gertrude announced their marriage and told Hamlet he was mourning too much. Tonight they are celebrating their marriage with a big party, the "drunken revelry" you mention in your question.
When Hamlet and the others are waiting for the Ghost to appear, they hear trumpets blasting, several gunshots and the sound of a great party. Horatio asks what these things mean, if anything. Hamlet explains the noise as being part of a wedding ritual in his country. The king will stay up all night, drinking and dancing as the noise and partying continues.
This heavy-headed revel east and west
Makes us traduced and tax'd of other nations:
They clepe us drunkards, and with swinish phrase
Soil our addition; and indeed it takes
From our achievements, though perform'd at height,
The pith and marrow of our attribute.
So, oft it chances in particular men,
That for some vicious mole of nature in them,
As, in their birth--wherein they are not guilty,
Since nature cannot choose his origin--
By the o'ergrowth of some complexion,
Oft breaking down the pales and forts of reason,
Or by some habit that too much o'er-leavens
The form of plausive manners, that these men,
Carrying, I say, the stamp of one defect,
Being nature's livery, or fortune's star,--
Their virtues else--be they as pure as grace,
As infinite as man may undergo--
Shall in the general censure take corruption
From that particular fault: the dram of eale
Doth all the noble substance of a doubt
To his own scandal.