Back in the analog days, TV technology was very stable. It barely changed from one decade to the next. But in our digital world today, there can be significant technology changes from one decade to the next. At least, it might happen that way.
In the U.S., TV technology standards are developed and documented by the Advanced Television Systems Committee (ATSC). We are in the middle of ATSC 1.0, with a possible evolution to ATSC 2.0 and then ATSC 3.0.
Much of ATSC 1.0 is derived from work done in the 1990s by the Moving Picture Experts Group (MPEG), an international standards body. ATSC extended this work and adopted the U.S. digital television standards in the mid-1990s.
ATSC 1.0 has several essential elements. The modulation is 8-VSB, with a single carrier occupying a 6 MHz channel. The audio coding specification is Dolby AC-3 audio. And the video coding system is MPEG-2 video.
In Europe, the predominant digital television system is known as DVB-T (DVB stands for Digital Video Broadcasting.) It was documented in the mid-1990s by the DVB Project, an alliance of about 200 companies, and is also based largely on work done by MPEG.
In my view, there are two significant differences between DVB-T and ATSC 1.0 – modulation and audio coding. While ATSC 1.0 uses 8-VSB modulation, DVB-T uses orthogonal frequency division multiplexing (OFDM), in which the channel bandwidth is occupied by thousands of narrow bandwidth carriers. And instead of the Dolby audio coding, DVB-T uses an audio coding system developed by Fraunhofer.
In 2010, ATSC began the planning for ATSC 2.0. ATSC 2.0 will be based on ATSC 1.0, with several new features tacked on. The 8-VSB modulation won’t change, so existing digital TV sets will continue to work, but they won’t get the new features. One new feature is interactivity. Viewers will be able to interact with content and applications stored in the TV set, or downloaded from the broadcasters’ servers. Another new feature is viewing of program files that were downloaded into TV sets in advance, as opposed to programs streamed in real time.
ATSC 2.0 will support use of “second screens” such as tablet computers. The “primary screen” TV set will communicate with “second screen” devices over home networks. And ATSC 2.0 will support the Advanced Video Coding (AVC) system developed by MPEG (also known as H.264). AVC video coding is already being used by Dish, DirecTV and AT&T’s cable systems. Also, advanced audio coding will be supported, including Dolby E-AC-3, Fraunhofer’s HE-AAC and an audio coding system developed by DTS, Inc.
ATSC 2.0 will consist of a suite of standards. They have not yet been adopted in final form, but several are available to review as candidate standards. ATSC hopes that final versions will be adopted and published sometime in 2014.
It remains to be seen whether TV set manufacturers will build any TV sets that support the added ATSC 2.0 features, because in late 2011, ATSC began planning for ATSC 3.0. The goal for completion of ATSC 3.0 is December 2015, not long after final standards for ATSC 2.0 are done.
While this work was going on in the U.S., in Europe they were developing an advanced television system called DVB-T2. Based on information that ATSC has released, the emerging picture of ATSC 3.0 resembles a combination of ATSC 2.0 and DVB-T2.
DVB-T2 uses a video coding system called High Efficiency Video Coding (HEVC) that is even more efficient than AVC. This can deliver UHDTV (also known as 4K) in a 6 MHz channel. It uses an advanced version of the Fraunhofer audio coding system that incorporates “immersive” sound. This system delivers 22 channels of audio, some of which may be overhead. Dolby and DTS have developed competing versions of “immersive” sound.
DVB-T2, like DVB-T, uses OFDM modulation, and most likely ATSC 3.0 will use OFDM. That means that existing U.S. TV sets won’t be able to receive the signals.
And that raises the question of a transition. When we moved from analog to digital TV broadcasting, broadcasters were given a second TV channel, so they had one for their analog signal and one for their digital signal. By putting up digital signals on a second channel, broadcasters solved the chicken-and-egg problem. Consumers could go out and buy digital TVs with the assurance that there would be digital programming to watch.
That’s not the case for a transition to ATSC 3.0. There is no second channel available. Consumers may be willing buy a dual-mode TV set that receives both 8-VSB and OFDM signals, if the price differential isn’t too steep. But no rational broadcaster will be willing to shut off his 8-VSB signal and replace it with an OFDM signal until a substantial number of OFDM-capable TVs sets have been deployed.
I’d say U.S. broadcasters are looking at a significant chicken-and-egg problem.