SMPTE ST 312:2001

Abtract:

This standard defines constraints on the encoding of and syntax for MPEG-2 transport streams such that they may be spliced without modifying the PES packet payload. Generic MPEG-2 transport streams, which do not comply with the constraints in this standard, may require more sophisticated techniques for splicing. — The constraints specified here are applied individually to programs within transport streams. A program is a collection of video, audio, and data streams which share a common time base. The presence of a video component is not assumed. The standard enables splicing of programs within a multiprogram transport stream either simultaneously or independently. Splice Points in different programs may be presentationtime-coincident, but do not have to be. The standard may also be used with single-program transport streams. — The document specifies constraints for both seamless and nonseamless Splice Points. Seamless Splice Points must adhere to all the constraints. Nonseamless Splice Points must adhere to all constraints except those prefaced with the clause “to enable seamless splicing.” A bit stream which is compliant with this standard shall conform to the constraints defined in clauses 5 and 6. Such a bit stream may contain any number of seamless, nonseamless, or both types of Splice Points. If a bit stream does not contain splice event command and control information, the constraints in clause 7 do not apply to the bit stream. Mechanisms for transmission of time code in MPEG-2 transport/elementary bit streams shall be addressed by other standards. — In addition to constraints for creating spliceable bit streams, this standard specifies the technique for carrying notification of upcoming Splice Points in the transport stream. A splice information table is defined for notifying downstream devices of splice events, such as a network break or return from a network break. The splice information table which pertains to a given program is carried in a separate PID stream referred to by that program's program map table. In this way, splice event notification can pass through transport stream remultiplexers without need for special processing. A bit stream which is compliant with this standard and which carries splice event command and control information shall conform to the constraints in clauses 5, 6, and 7. — The standard does not address constraints on splicing devices. Annex A outlines several issues that should be considered in the design of such devices. — NOTE – Numbers given in brackets are subject to confirmation.