CEA-708 - Packets in CEA-708

Packets in CEA-708

Caption streams are transmitted with many packet wrappers around them. These are the picture user data, which contains the caption data, which contains the cc_data, which contains the Caption Channel packets, which contains the Service Block, which contains the caption streams. These packets are described in detail in this section. But the streams themselves are described in the following sections.

This layering is based on the OSI Protocol Reference Model:

OSI Layers	DTVCC Layers	Comments
Application	Interpretation	Issuing commands and appending text to windows
Presentation	Coding	Breaking up individual commands and characters
Session	Service	Service Block Packets
--	Packet	DTVCC Packet assembly from cc_data Packets
Transport	Transport	cc_data Packets, and encapsulation in picture user data
Network	--	--
Link	--	--
Physical	--	--

This section will describe the various packets, the Coding Layer and Presentation Layers are described in the remainder of this document.