SIP SDP Codec Overview

• Purpose

• Architectural Relationships

• Description of the interface class structure

• Memory overhead

When initiating multimedia teleconferences, voice-over-IP calls, streaming video, or other real-time sessions, there is a need to convey media details, transport addresses, and other session description metadata to the participants.

SDP, or (S)ession (D)escription (P)rotocol, provides the standard representation for such information. This representation is independent of the way that information is transported.

Transport protocols that can deal with SDP include SAP, SIP, RTSP, electronic mail using the MIME extensions, and HTTP.

The SDP Codec subsystem offers its clients an API for encoding SDP descriptions into their internal form, for decoding the descriptions from their internal form, and for setting and getting SDP field values.

You may find the following references useful:

• Multiparty Multimedia Session Control (mmusic)

• Real Time Streaming Protocol (RTSP)

• Integration of Resource Managemnt and Session Initiation Protocol (SIP)

• Grouping of Media Lines in the Session Description Protocol (SDP)

• An Offer/Answer Model with the Session Description Protocol (SDP)

Calls to the SDP Codec API are synchronous.

The API requires no capabilities.

The API cannot be extended.

The client uses some or all of the SDP Codec API classes during the handling of a SDP description.

Interface classes all derive from CBase.

The client has a 'use' relationship with the SDP Codec API library.

The following diagram shows the SDP Codec API class structure.

The amount of overhead memory used by every header object of the SDP Codec API is at least the same as the memory used by the header as text.