RTP Interleaving Colin P erkins < c.p erkins@cs.ucl.ac.uk > - PowerPoint PPT Presentation

RTP Interleaving Colin P erkins < c.p erkins@cs.ucl.ac.uk > Depa rtment of Computer Science Universit y College London Go w er Street London W C1E 6BT

The interleavin g p ro cess Original Stream 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Interleaved Stream 1 5 9 13 2 6 10 14 3 7 11 15 4 8 12 16 Packet Loss 1 5 9 13 2 6 10 14 3 7 11 15 4 8 12 16 Reconstructed Stream 1 2 4 5 6 8 9 10 12 13 14 16 Distributes loss, making one la rge loss app ea r as several � smaller losses Useful if latency is not an issue, bandwidth e�cient � Colin P erkins/RTP Interleaving/1

P ack etisation options T o reconstruct the stream, the receiver must kno w the interleaving function. Tw o w a ys of conveying this info rmation: where the session description conveys the Implicit interleaving function, and the pack et sequence numb er determines the p osition in the sequence. where each pack et contains the relative p osition of Explicit each frame in the sequence. Colin P erkins/RTP Interleaving/2

Implicit pack etisation Advantages Minimal bandwidth overhead � Disadvantages Interleaving function is �xed fo r the duration of a session � Need to kno w talkspurt sta rt to determine p osition in the � sequence, can cause p roblems if �rst pack et is lost Colin P erkins/RTP Interleaving/3

Explicit pack etisation Advantages Interleaving function can change during a session � Can build a common deco der fo r interleaved and � redundant streams (RF C2198) Each pack et is indep endently deco dable � Disadvantages Overhead due to the timestamp info rmation (4 b ytes p er � frame) Colin P erkins/RTP Interleaving/4

Prop osal Reuse the pa yload fo rmat fo r redundant audio, to enco de � interleaved streams (draft-ietf-avt-interl eavi ng-00.txt). Deco ders fo r this fo rmat should b e able to deco de such � streams without mo di�cation. Mak e this an explicit requirement in the next revision of � RF C2198. Colin P erkins/RTP Interleaving/5