Motivation

Television distribution operators such as cable television operators video distributors and broadcasters normally receive several programme signals from different local or remote sources, and they switch the appropriate signal at the appointed time, on each output channel of their television transmission system to accommodate local advertisements, local programming, emergency messages, etc.

Several programme signals are often multiplexed with each other for multicast distribution purposes, which utilize distribution network resources effectively. And the multiplexing may dynamically vary due to a condition of programme requests from viewers namely in VoD service. A targeted service such as a programme promotion and an advertisement, which provides different content¹ to each viewer based on his programme preference, also needs a delivery control based on this dynamic multiplexing.

With the advent of digital television transmission systems, programme signals take the form of compressed audio-video signals such as MPEG-2 bit streams, and they would be delivered with a multiplexing mechanism, i.e. MPEG transport stream (MPEG-TS), which can be further encapsulated in IP packets. Television distribution operators such as cable operators will be confronted with the task to switch or multiplexing among the bit streams or TS/IP packet streams, without causing disruptive disturbances to home decoders, and preferably without incurring the artefacts attendant to multiple cascaded encoding and decoding.

The problem is compounded by the fact that the various programme bit streams at the input of a digital programme delivery function will likely be out of synchronization with each other; they may use different bit rates, different resolutions different picture formats and different types of packet, namely IP or TS packet and possibly conform to various different profiles or levels of each compression coding standard.

The problem is further compounded by the fact that programme distributers may wish to edit among compressed bit streams using some simple visual transitions, such as cross-fades, wipes, etc.

Television distribution systems have been moved to digital operation. It is important and urgent to study the operating requirements for programme delivery controls such as multiplexing, switching and insertion of compressed programme bit streams and/or IP/TS packet streams into different programme streams at content distribution functions such as cable television head-ends. Cost effective and operationally efficient solutions should be found to meet those requirements, and they should be reflected in any international standardization that may be required in order that those solutions may be readily and uniformly implemented.

Another important consideration is the replication or reuse of existing analogue functionality in the digital programme insertion system. All the attendant monitoring, auditing and control functions in widespread use today should be accommodated in any digital system that supports equivalent applications such as local advertising, local programme insertions, or emergency message insertion in the analogue domain.

Question

Study items to be considered include, but are not limited to the following ones.

What are the functional and operational requirements of the various applications that must be met for delivery control of different compressed programme bit streams and/or TS/IP packet streams on the output channel of television distribution systems such as multiplexing, switching, and insertion?

Which technical solutions can be recommended to allow the delivery control such as multiplexing, switching and insertion of different compressed programme bit streams and/or TS/IP packet streams on the output channel of television distribution systems:

• without causing disruptive disturbances to home decoders;

• without incurring the programme quality losses attendant to repeated compression encoding and decoding, while at the same time meeting the specified operating requirements, e.g.
  • allowing simple visual transitions between switched programmes,
  • allowing independent switching of the video, audio and data present in the compressed bit stream and/or TS/IP packet stream multiplex,
  • allowing bundling of multiple programmes on the bit stream domain and/or TS/IP packet stream domain with taking advantage of statistical characteristics of each programme,
  even when the various bit streams:
• are not synchronized to each other,
• use different bit rates and resolutions,
• conform to different picture formats and profiles,
• conform to different compression standards
• are encapsulated in TS or IP streams?
• what enhancements to existing Recommendations are required to provide energy savings directly or indirectly in Information and Communication Technologies (ICTs) or in other industries? What enhancements to developing or new Recommendations are required to provide such energy savings?

Tasks

Tasks include, but are not limited to the preparation of a number of draft new Recommendations by the end of this Study Period.

An up-to-date status of work under this Question is contained in the SG 9 Work Programme.

Relationships

Cooperation should be established with ITU-T Study Group 16 and ITU-R Study Group 6 when appropriate, and with the IEC/ISO in the study of this Question.