1.3 Overview

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H26XPF specifies the payload format for encapsulating an H.261 [H261] bitstream and two payload formats for encapsulating an H.263 [H263] bitstream in the Real-Time Transport Protocol (RTP/RTCP): Microsoft Extensions [MS-RTPME].

The payload format for H.261 video streams is an extension to the H.261 payload format [RFC2032]. RTP is used to carry H.261 payloads. The Session Description Protocol (SDP) [MS-SDP] and H.245 [H245] are used to negotiate codec usage.

The payload formats for H.263 video streams are an extension to the H.263 payload format [RFC2190]. H26XPF specifies two modes for encapsulating H.263 video streams: RFC mode and draft mode. RFC mode supports mode A and mode B of the H.263 video payload header with some constraints. The payload format for H.263 video streams in draft mode differs from RFC mode in that it supports a different H.263 payload header format. RTP is used to carry H.263 payloads.

RFC mode of the H.263 payload format is used in conjunction with the Session Initiation Protocol (SIP) [MS-SIP] application layer control protocol. SDP is used to negotiate codec usage with SIP. Draft mode of the H.263 payload format is used in conjunction with the H.323 [H323] application layer control protocol. H.245 is used to negotiate codec usage with H.323.