This is Dona Selma do Côco with her group performing one of their songs. In concert they would be doing some really cool dance moves that go with it. Anyways, this is one of the manifestations of the Baião rhythm. The basic zabumba rhythm (does some variations on this) is x..X..x. Big X is an accent.
The The instrumentation is Zabumba, pandeiro, ganzá, and 3 atabaques (from what I can tell)