add glossary page for SAP

docs/glossary/sap.md

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+# SAP
+
+SAP is an accronym which in the context of media streaming, can stand either for *Stream Access Points* or *Session Announcement Protocol*. In this wiki, SAP typicaly refers to the former.
+
+
+## Stream Access Points
+
+In the context of media packaging, stream access points enable random access and rendering of a stream in a media container.
+
+Refer to Annex I of ISO/IEC 14496-12:2022 for the exact definition of the different types of Stream Access Points.
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+
+
+## Session Announcement Protocol
+
+A protocol used for the announcement of multicast multimedia sessions, including video and audio streams. The protocol helps clients discover available streams and access information about them, such as stream locations, encoding formats, and timing.
+
+It is typically used alongside other protocols, such as RTP (Real-time Transport Protocol) for the actual media delivery, to handle session announcements and stream information dissemination.
+
+SAP was published by IETF as [RFC 2974](https://datatracker.ietf.org/doc/html/rfc2974) in 2000.