Blocos heat up before Rio's Carnival

Rio de Janeiro's Carnival officially begins on Saturday.

But the city's streets are already crowded with thousands of people following its "blocos" or street parades.

The "blocos" are booming in popularity, as they provide a casual, cheap and local alternative to the main events downtown in the Sambadrome.

Once small affairs, some of the "blocos" now involve up to two million people.

Miguel Costa, an organiser of one of the city's oldest and most traditional "blocos", tells the BBC about the importance of the street parties and why Cariocas - the people of Rio de Janeiro - love Carnival.