More content down the same pipe

Improving audio and video coding allows more and higher quality multimedia content

By Morand Fachot

Over the last two decades digitization of multimedia product content has offered global access to a progressively wider choice of services and better audio and video. The most visible aspect of advances in broadcast technology is the availability of new equipment, which relies on standardization work from many IEC TCs (Technical Committees). Another less evident, but no less significant, component has been the rollout of successive versions of ever more efficient digital compression coding/decoding standards.

Viewers can access more higher-quality content thanks to digital compression (Photo: Sony Corp.)

More services, better quality

As many countries started opening up their broadcast landscape in the 1980s with the launch of commercial broadcasting, they gradually came up against the prospect of a spectrum bottleneck. This is because analogue signals use up a large amount of bandwidth. To overcome analogue broadcasting limitations in terms of services and quality, compression standards that could be used in digital broadcasting and other applications were developed.

MPEG (Moving Picture Experts Group), a working group of experts, was formed by the IEC and ISO (International Organization for Standardization) in 1988 to prepare these types of Standards jointly with ITU-T (International Telecommunication Union Telecommunication Standardization Sector) Study Group 16, Multimedia, also known as VCEG (Video Coding Experts Group).

ISO/IEC 11172-1, the first of the Group's five-part series, also known as MPEG-1, was published in 1993 by ISO/IEC JTC (Joint Technical Committee) 1/SC (Subcommittee) 29: Coding of audio, picture, multimedia and hypermedia information.

MPEG-1 covers the coding of moving pictures and associated audio for digital storage media at up to 1,5 Mbit/s or so.

The first of the ten-part ISO/IEC 13818 series, or MPEG-2, also known as ITU-T (Recommendation) H.262, which provides additional features such as support for interlaced video, was published in 1996. It is the most widely used format for digital television signals broadcast over-the-air (DTT, or digital terrestrial TV), cable and DTH (direct to home) satellite transmission, as well as for other applications such as DVDs.

Digital compression offered a significant advantage as demand for more services increased rapidly. For instance, a single 30-36 MHz satellite transponder used for DTH could carry just one analogue channel, but up to 16 digital channels encoded in MPEG-2, making satellite broadcasting much more cost effective and also resulting in more efficient use of the terrestrial frequency spectrum.

Improving efficiency

ISO/IEC 14496, the series of Standards known as MPEG-4, further improved on MPEG-2, in particular as regards digital video coding. MPEG-4 Part 10, advanced video coding, or AVC, also known as ITU-T H.264 or MPEG-4/H.264 AVC, reportedly provides the same quality as MPEG-2 with less than half the bitrate.

AVC is used in Blu-ray Disc and stereoscopic 3D video content.

Another digital multimedia format, MPEG-4 Part 14, better known as MP4, is also widely used to store video, audio and associated data, such as subtitles. In addition it allows streaming over the Internet.

The latest digital compression coding/decoding standard of the same family, ISO/IEC 23008-2, High efficiency video coding (HEVC), or ITU-T H.265, was published in December 2013. It will allow the storage and distribution of UHDTV (ultra high definition TV) content. The term UHDTV covers both so-called 4K (offering twice the horizontal and vertical resolution of the 1080p HDTV format and four times as many pixels), which is currently being rolled out, and future 8K (four times the horizontal and vertical resolution of 1080p and 16 times as many pixels).

4K was the most popular innovation trend presented at this year's CES (Consumer Electronics Show) in Las Vegas, according to an analysis of the Twittersphere, an indication of growing interest from both industry and consumers.

MPEG-2 still Standard of choice

MPEG-2 is still widely used, in particular for SD (standard definition) content. According to a study by the satellite industry Market Research and Consulting company NSR (Northern Sky Research), 73% of the 23 182 SD channels it attributed to the global satellite market as of the end of 2012 were still broadcast in MPEG-2 or another similar format.

However, NSR notes that no less than 86% of the 3 836 HD/3D channels carried globally at the end of 2012 were broadcast using MPEG-4 encoding. To a large extent this trend was also observed for similar channels broadcast via DTT or cable.

As is often the case, the first regions/countries to adopt a technology are likely to be the heaviest users years after newer technologies are introduced. Some 80% of SD channels in North America and 90% in Western Europe use MPEG-2 encoding compared to regions like Sub-Saharan Africa or South Asia where about half of the current SD channels are being carried in MPEG-4.

This tends to show that new technologies do not always displace older ones, but operate alongside them whilst also opening up new opportunities. MPEG-2 made possible the introduction of more channels in better definition compared to analogue broadcasts; MPEG-4/AVC allowed more HDTV channels and 3D content; HEVC is now paving the way to UHDTV, but MPEG-2 is still widely deployed.

International recognition

The economic impact of the digital compression coding/decoding Standards prepared jointly by ISO/IEC MPEG and ITU-T SG 16 cannot be overemphasized. A highly significant and growing share of the global broadcast media industry market, which is expected to reach nearly USD 600 billion in 2017, relies entirely on these Standards.

This contribution to the industry has been recognized by the US National Academy of Television Arts and Sciences (NATAS) which gave MPEG an engineering Emmy Award for its work on "International Standardization of JPEG, MPEG-1 and MPEG-2" in 1996, and two additional Emmys in 2008 and 2009 covering, respectively, MPEG-1 and MPEG-2 coding associated with video, CD and MP3, digital TV, set top boxes and DVD, and MPEG-4 AVC .

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