Negotiating Simultaneous Modalities in Real-Time Communications

In a real-time communication session, there may be a need or preference for receiving the same content in two or more simultaneous modalities. This specification extends a mechanism for human language negotiation with a mechanism for indication of preference for, or the availability of, simultaneously provided transformations of original contents. This indication enables negotiation of simultaneous modalities in real-time sessions. Applications are for example provision of both spoken and written content in a real-time call (captioning), or provision of both spoken language original and sign language interpretation of the original language in a real-time session.