1 © 1999, Cisco Systems, Inc. Course Number Presentation_ID MP2T Extension to RTP Humphrey Liu

2 IETF-Washington © 1999, Cisco Systems, Inc. What’s the Issue? MP2T is packet-based transport format. It can contain multiple programs. It can also contain multiple data Aggregate bandwidth can be as high as 50-60Mbps(  40Kpps). 90KHz defined in RFC2250 does not have reasonable resolution for every MPEG packet.

3 IETF-Washington © 1999, Cisco Systems, Inc. Why 27MHz? It’s clock frequency defined by MPEG2. Most of the existing MPEG2 encoders, muxes, and decoders have 27MHz clock. It can be used for packet draining clock as well (seamless to DVB-ASI).

4 IETF-Washington © 1999, Cisco Systems, Inc. How to Use It? Clock recovery. Calculation of piece-wise CBR bitrate pwRate = nPkts * 1504 / (ts2-ts1)/27M Interpolation of timestamp for every MPEG packet Output pkt stream  src MPEG stream (clock mismatch)

5 IETF-Washington © 1999, Cisco Systems, Inc. Piece-Wise CBR

6 IETF-Washington © 1999, Cisco Systems, Inc. Piece-Wise CBR BW = Mbps

7 IETF-Washington © 1999, Cisco Systems, Inc. Buffer Model Dejitter Buffer MPEG TS Buffer Muxing Buffer Elem. Buffer RTP Packet MPEG TS packet MPEG PES pkt MPEG comp. layer

8Presentation_ID © 1999, Cisco Systems, Inc.