scope:

Introduction

The MPEG-2 Transport System Target Decoder (T-STD) buffer model is defined for the Synchronized Download protocol. The buffer model includes a secondary multiplexing stage based on the tableid-extension field of the DSMCC section structure. The secondary multiplexing stage allows multiple data modules of a single program element to be independently synchronized.

A secondary channel is referenced as a data module channel. The table_id-extension field conveys a copy of the moduleId of the data module. Each data module channel is identified by the moduleId value shared by all data modules conveyed in this data module channel.

The primary, conventional multiplexing stage uses the MPEG-2 Transport Stream packet's PID value to forward the packet payloads to their respective smoothing buffer. The payloads of the Transport Stream packets are all portions of DSM-CC sections of a program element of stream-type value 0x14. The DSM-CC sections convey Download Control messages or Download Data messages. Download control messages are conveyed in sections with tableid value Ox3B while Download Data messages are conveyed in sections with tableid value Ox3C. The section_number field identifies the block number of the data module conveyed in the section. The payloads of the DSM-CC section sharing the same table_id, table_id_extension and version_number field values are re-assembled in-order in the receiver to reconstruct the synchronized data modules.