Grouping of Media Lines in the Session Description Protocol (SDP) [RFC 3388]

Defines two SDP attributes:

"group" and
"mid" - media stream identification

Allows grouping several media ("m") lines together. This is to support:

Lip Synchronization (LS) and
Flow Identification (FID) - a single flow (with several media streams) that are encoded in different formats (and may be received on different ports and host interfaces)
- Changing between codecs (for example based on current error rate of a wireless channel)

Note FID does not cover the following (but SDP can -- see RFC 3388):

Parallel encoding using different codecs
Layered coding

Slide Notes

[RFC 3388] G. Camarillo, G. Eriksson, J. Holler, and H. Schulzrinne, ‘Grouping of Media Lines in the Session Description Protocol (SDP)’, Internet Request for Comments, vol. RFC 3388 (Proposed Standard), Dec. 2002 [Online]. Available: http://www.rfc-editor.org/rfc/rfc3388.txt Links to an external site.

Transcript

[slide200] Now, we can group these things, and the purpose we said of that was to support things like lip synchronization. We can have flow identifiers, etc.