TUTORIAL: SEPTEMBER 24, 2007
IPTV: What’s Behind The Acronym?
Is it really possible to send HDTV programs to your home without a terrestrial DTV receiver, cable TV set-top box, or satellite dish? Not only is it possible, it may become the preferred way to watch HDTV on everything from your cell phone to your laptop.
Earlier this month, I managed to spend a day at the International Broadcasting Conference (IBC), held at the sprawled-out and overfull RAI Center in Amsterdam, The Netherlands.
In additional to the usual booths from electronics giants such as Sony, Thomson, Cisco, Philips, and others that were peddling cameras, editing gear, switchers, and other broadcast essentials, there were several stands and exhibits devoted to a pair of “hot” emerging technologies — mobile digital TV, or DVB-H in Europe, and IPTV.
For that matter, there was one entire hallway of exhibits on IPTV, with small booths manned by companies pushing software and hardware solutions to a market that is barely learning how to walk for the first time. Those readers who attended NAB a few years back and saw the plethora of streaming media pavilions would have winced at this grand case of déjà vu.
As is so often the case these days, everyone’s abuzz about technology that few really understand. IPTV sounds like a whole new way to move video and audio from content provider to the home, but it really isn’t. For that matter, much of the infrastructure is already in use by terrestrial, cable, and satellite networks and broadcasters.
In the USA, only two IPTV service providers are in operation, and on a very limited basis. Verizon, the telecommunications giant, offers video through their FiOS service, which also carries telephone and broadband. But the “video” part of it isn’t really IPTV at the present time.
The other player is just finishing up preliminary tests on a pure IPTV delivery system. It’s AT&T, owned by SBC of Kansas City, and U-Verse is the name by which the system is known. You’ve probably seen the advertising for it on TV and in print, with viewers simultaneously using cell phones, laptops, and conventional HDTVs to watch a football game.
How is this possible? Is it a pipe dream, or science fiction? The answer is — yes, you can deliver standard-definition and high definition TV to cell phones, PDAs, laptops, desktops, and TV sets, all at the same time, all using the same protocol — IPTV.
The “IP” part stands for “Internet Protocol.” You know, that TCP/IP stuff that allows you to go out on the Internet, send and receive mail, print documents through an 802.11 connection, and communicate with and control displays, audio equipment, screens, and other AV gadgets from a Web browser.
In the IP world, every device connected to a wired or wireless network has a unique address. Sometimes a computer or a router automatically sets that address, such as with dynamic host control protocol (DHCP). Other times, it is manually specified and will never change. But that IP address is the key to making IPTV work.
In an IPTV system, digital video and audio are coded and decoded using standards like MPEG. In MPEG, streams of packets that are intermixed make up the elements of a TV program. The video travels with one set of numbers, the audio with another, and ancillary data such as an electronic program guide has yet another set of numbers.
Figure 1. MPEG program allocation and mapping tables are the keys
to transporting video and audio through a digital TV system.
MPEG program numbers are different than IP addresses, and refer to specific packets. IP addresses refer to specific pieces of hardware, such as a laptop, camera, or DVR. Both are needed to move content through an IPTV system from head end to subscriber.
MPEG program numbers are used for everything from DVDs to terrestrial broadcasts and follow a specific paradigm. Two tables that travel along with the stream of audio and video help to identify the packets. The first table is called the Program Association Table, or PAT, and identifies all of the packet identifiers (PIDs) carried in the digital stream. Think of it as the “parts list.”
The second table is the Program Map Table, or PMT. This table specifies which video, audio, clock, and data packets are to be lumped together to create a “channel’ or “show.” Think of it as the “assembly instructions.” (The actual PIDs are identified with hexadecimal coding.)
So, a HD broadcast of a football game might be identified as PID 48 in the PMT, and consist of an HD video stream (PID 0x0041) and a Dolby Digital AC-3 audio soundtrack (PID 0x0044). The receiver picks off any packets using these PIDs and re-assembles them into an HD picture with 5.1-channel surround.
Figure 2. Here are sample MPEG program numbers for WNBC-DT’s HDTV program service.
Note the hexadecimal codes and PIDs, highlighted in green.
That’s exactly the system used to distribute digital TV via cable, satellite, or terrestrial connections. And RF doesn’t have to be the transmission medium, as the only real issue is bandwidth. It stands to reason that the MPEG packets can be moved in other ways, such as over a fiber optic connection, or through fast and wide wireless nodes.
In that case, the MPEG structure remains the same. But the receiver must have an IP address so that the content provider can deliver the programming. Of course, any device that can decode the MPEG packets and encode them to video and audio can play back a TV show, which is why you see the simultaneous use of a cell phone, laptop, and HDTV in the AT&T commercials
Do you have a package at home that delivers both broadband and TV content through the same wire? With IPTV, you could dump the TV service and rely exclusively on the broadband connection, if it was fast enough (and most aren’t).
That’s a scary thought to cable system operators like Comcast and Time Warner, which is why both are fighting efforts by Verizon and AT&T to skirt time-intensive municipality-by-municipality franchise agreements and simply obtain a statewide franchise to begin wiring up and delivering their IPTV services.
As I mentioned before, Verizon isn’t really delivering pure IPTV — yet. For now, their video services, which do travel over a high-speed fiber optic backbone, employ the same quadrature amplitude modulation system used by cable companies. Eventually, the company will shift to 100% IP addressing of MPEG packets.
In contrast, AT&T’s system is 100% IPTV, but is only rolling out on a limited trial basis as of this writing, presumably to get all the bugs out of the set-top receivers, program guide, and content provider screw-ups which include re-booting encoders and changing MPEG program numbers unexpectedly.
Even so, the crowd of IPTV wannabes is getting bigger and bigger with each passing month. At IBC, Motorola, Cisco, Pace, Thomson, Samsung, and others all showed IPTV set-top receivers. Numerous companies had demonstrations of customized electronic program guides, while others showed multi-platform encoding software and hardware to optimize viewing for both small and large screens.
Provided enough bandwidth is available, IPTV could replace many of the older video delivery systems we’ve come to know and love. It’s likely cable companies would eventually move to 100% IP distribution of TV content if Verizon and AT&T are successful. Even DirecTV and Dish could soon be competing with terrestrial wireless delivery of broadband services, such as the system cellular pioneer Craig McCaw is developing.
According to one Web site, “…in 2003, Craig McCaw founded Clearwire, a wireless broadband Internet service provider. A fast, portable alternative to the cable modem and DSL services provided by cable television and telephone companies, Clearwire uses WiMAX wireless technology to transmit from a network of mobile phone towers. Users can access the Internet wherever they are, without connecting to a land-based cable or telephone system. As of this writing, Clearwire is active in dozens of U.S. markets, as well as Mexico, Belgium, Denmark and Ireland.”
You can be sure that, where there’s fast broadband, IPTV is sure to follow”
