the application level protocol
The protocol that is generated by the playout server for the transmission of the files and live streamed videos implement a large number of features that have to be shown useful for unicast protocols as is implemented here. As for DVB networks, the transmission quality is not assured and whether conditions can largely effect the transmission quality, the reduction of transmission errors is one of the main features of the application level protocol that is implemented in the protocol. As this protocol is send by the server and is received by the DVB receivers it has to take the processing power of the receiver site into account. Thus, the algorithms have to be efficient in a sense that they do not require to much processing overhead as the receiver site is usually defined by a set-top-box system.
The following features are mainly important for the application level protocol:
Scalable Forward error correction (standard forward error correction rate 12 %) Distribution of content to target groups Groups can be formed dynamically, i.e. a receiver client can be joined to a group / can be dropped out from a group Files can be submitted and reception is acceptable for receiver if a given maximal number of packets is lost (for MPEG video, dropped packets can be tolerated) An optional return channel can be used to request missing data packets at the headend for retransmission via IP-over-DVB. The protocol allows for a maximal number of transmission rounds. If file is not received ok up to then, the transmission has failed Parallel delivery of files and live streaming using similar IP-over-DVB channel but different target groups. I.e. in parallel to a live streaming of MPEG data (using IP-over-DVB), the same channel can be used to transmit data files to the receiver clients. The target groups of the live TV channel and the file transmission can be different.