ST 325:1999 - SMPTE Standard - For Digital Television — Opportunistic Data Broadcast Flow Control

This standard defines the flow control protocol to be used between an emission multiplexer and data server for opportunistic data broadcast. Opportunistic data broadcast inserts data packets into the output multiplex to fill any available free bandwidth. The emission multiplexer maintains a buffer from which it draws data to be inserted. The multiplexer will request additional MPEG-2 transport packets from the data server as its buffer becomes depleted. The number of packets requested depends upon the implementation, with the most stringent requirement being requesting a single MPEG-2 transport packet where the request and delivery can occur in less than the emission time of an MPEG-2 transport packet from the multiplexer. This protocol is designed to be extensible and provide a basis for low-latency, real-time backchannel communications from the emission multiplexer. — Encapsulated in MPEG-2 transport packets, the messages of the flow control protocol are transmitted via MPEG-2 DSM-CC sections, following the message format defined in ISO/IEC 13818–6, chapter 2. Such sections provide the capability to support error correction or error detection (or to ignore either).