Towards an RTP Profile for IPTV

In this paper we analyze the two major transport protocols that are currently under discussion for IPTV and propose extensions to support convergence. On the one hand, the MPEG-2 transport stream (MPEG2-TS) is well established in the broadcast world, whereas the real-time transport protocol (RTP) is widely adopted in the Internet and mobile world. Our analysis focuses on the timing aspects such as synchronization and buffer management. It is shown that the system target decoder (STD) defined in MPEG2-TS provides a well defined decoder model that allows minimum buffering delay and predictable behavior. In contrast, an RTP receiver is intentionally defined less accurately to allow flexibility for multiple applications. However, this flexibility results in less clear receiver behavior which is a problem for the design and integration of IPTV systems. By comparing the main differences in the timing models of the two protocols we derive additional constraints and definitions for RTP that minimize the difference to MPEG2-TS. It is proposed to specify these changes as part of an RTP/IPTV profile which also defines an RTP system target decoder (RTP-STD). An example for the application of these extensions is a protocol gateway supporting the convergence of broadcast and the Internet world in IPTV.