| 摘要 |
Two additional structures for addition to the Digital Video Broadcasters (DVB) Service Information (SI) for implementation of the MPEG-2 Systems Standard (ISO/IEC 13818-1 are provided: the Logical Channel Table (LCT) and the Composite Channel Table (CCT). The LCT provides the mapping between a Logical Channel Number (LCN) representing a service and the transport stream/program number on which the service can be found. LCT entries may designate either simple conventional channels or Composite Channels. The LCT contains a Composite Channel Indicator (CCI), which when set to '1', indicates that the selected channel is a composite channel. In this case, the LCT entry gives the home channel of the Composite Channel, which provides the CCT to the decoder so that the tuner can be retuned to the actual program designated in the CCT for current viewing. Each entry in the CCT associates a Composite Channel Number (CCN) with a LCN and represents the "present" definition for the composite channel. A simple LCN is used as a key to the LCT to determine the transport stream ID and program number for the service components in the usual way. As time progresses, the entry for a specific CCN will change; therefore, the CCN is used as a "pointer" to the LCN which is the currently active service for the composite channel. These tables work with conventional MPEG-2 service definitions to decode multi-service transport streams. |
