Introduction

A standard is developed, published and used. Is that the end of the story for MPEG? It is not the end but the continuation of the same story. Indeed good standard must satisfy industry needs, but their use stimulates more needs that the standard must satisfy.

Here I will describe how this impacts the life of one of MPEG’s most prestigious standards: MPEG-2 Systems, which has turned 26 in November 2018 and has played a major role in creating the digital world that we know.

What is MPEG-2 Systems?

When MPEG started, standards for compressed video and later audio were the immediate goal. But it was clear that the industry needed more than that. So, after starting MPEG-1 video compression and audio compression, MPEG soon started to investigate “systems” aspects. Seen with today’s eyes, the interactive CD-ROM target of MPEG-1 was an easy problem because all videos on a a CD-ROM are assumed to have the same time base, and bit delivery is error free and on-time because the time interval between a byte leaving the transmitter is the same as the time interval at its arrival at the receiver.

In July 1990, even before delivering the MPEG-1 standard (which happened in November 1992), MPEG started working on the much more challenging “digital television” problem. This can be described as: the deliver of a package of digital TV programs with different time bases and associated metadata over a variety of analogue channels – terrestrial, satellite and cable. Of course operators expected to be able to do the same operations in the network that the television industry had been accustomed to do in the several decades since TV distribution had become common place.

A unique group of experts from different – and competing – industries with their different cultural backgrounds and many countries, and some of them with the common experience of designing from scratch the MPEG-1 Systems standard, started the design the MPEG-2 Systems standards, again from a blank sheet of paper.

The impact of MPEG-2 Systems

MPEG-2 Systems is the container and adapter of the digital audio and video information to the physical world. It is used every day by billions of people who receive TV programs from a variety of sources, analogue delivery media and, often, digital as well (e.g. IPTV).

MPEG-2 Systems was approved in November 1994, at a time when some companies who could not wait had already made implementations before the formal release of the standard. That date, however, far from marking the “end” of the standard, signaled the beginning of a story that continues unabated today. Indeed, in the 26 years after its release, MPEG-2 Systems has been constantly evolving, while keeping complete backward compatibility with the original 1994 specification.

MPEG-2 Systems in action

So far MPEG has developed 34 MPEG-2 Systems amendments (i.e. additions of functionality to an existing standard), 3 additional amendments are close to completion and one is planned. After a few amendments are developed, ISO requests that they be integrated in a new edition of the standard. So far 7 MPEG-2 Sys­tems editions have been produced covering the transport of non-MPEG-2 native media and non-media data. This is an incomplete list of the transport functionality added:

1. Audio: MPEG-2 AAC, MPEG-4 AAC and MPEG-H 3D
2. Video: MPEG-4 Visual, MPEG-4 AVC and its extensions (SVC and MVC), HEVC, HDR/WCG, JPEG2000, JPEG XS etc.
3. Other data: streaming text, quality metadata, green metadata etc.
4. Signaling: format descriptor, extensions of the transport stream format (e.g. Tables for splice parameters, DASH event signaling, virtual segment etc.), etc.

Producing an MPEG-2 Systems amendment is a serious job. There is a need for experts with the full visibility of a 26 years old standard (i.e. don’t break what works) and the collaboration of experts of the carrier (MPEG-2 Systems) and of the data carried (audio, video etc.). MPEG can respond to the needs of the industry because it has the expertise of all components available in house.

MPEG-2 Systems Amendments

Table 8 reports the full list of MPEG-2 Systems amendments, The 1^st column gives the edition, the 2^nd column the sequential number of the amendment of that edition, the 3^rd column the title of the amendment and the 4^th the dates of the approval stages.

Table 8 – The MPEG-2 Systems Amendments

Conclusions

MPEG-2 Systems is probably one of MPEG standards least “visible” to its users. Still it is one of the most important enablers of digital television distribution applications impacting the life of billions of people and tens of thousands of professionals. Its continuous support is vital for the well-being of the industry.