1© 1999, Cisco Systems, Inc.

Course NumberPresentation_ID

MP2T Extension to MP2T Extension to RTPRTP

Humphrey LiuHumphrey Liu

2IETF-Washington © 1999, Cisco Systems, Inc.

What’s the Issue?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.

3IETF-Washington © 1999, Cisco Systems, Inc.

Why 27MHz?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).

4IETF-Washington © 1999, Cisco Systems, Inc.

How to Use It?How to Use It?

• Clock recovery.

• Calculation of piece-wise CBR bitratepwRate = nPkts * 1504 / (ts2-ts1)/27M

• Interpolation of timestamp for every MPEG packet

Output pkt stream src MPEG stream(clock mismatch)

5IETF-Washington © 1999, Cisco Systems, Inc.

Piece-Wise CBRPiece-Wise CBR

1000

MPEGpkt

MPEGpkt

MPEGpkt

MPEGpkt

MPEGpkt

RTPpkt

RTPpkt

6000

6IETF-Washington © 1999, Cisco Systems, Inc.

Piece-Wise CBRPiece-Wise CBR

1000

MPEGpkt

MPEGpkt

MPEGpkt

MPEGpkt

MPEGpkt

RTPpkt

RTPpkt

6000

1000 2000 3000 4000 5000

BW = 40.608Mbps

7IETF-Washington © 1999, Cisco Systems, Inc.

Buffer ModelBuffer Model

DejitterBuffer

MPEG TSBuffer

MuxingBuffer

Elem.Buffer

RTPPacket

MPEGTS packet

MPEGPES pkt

MPEGcomp. layer

Internet

8Presentation_ID © 1999, Cisco Systems, Inc.