Providing a conference call includes establishing a bidirectional first class stream for each of a set of first class endpoints. A second class stream is established for each of a set of second class endpoints. Mixed streams are generated using the bidirectional first class streams, and one or more mixed streams are broadcasted to the set of second class endpoints. A particular second class endpoint is determined to have a right to have its stream included in the mixed streams. The second class stream for the particular second class endpoint is mapped to a bidirectional second class stream for the particular second class endpoint. Next mixed streams are generated using the bidirectional second class stream.