The Wonderful Things About Triggers

By Leslie Ellis -- Multichannel News, 2/5/2001

It's not easy being an interactive trigger. Its journey is arduous, sometimes traversing as many as three distinctly different broadcast networks. On arrival, the trigger doesn't always (or even often) get a warm welcome, because most of today's set-tops aren't equipped to see it on the threshold.

Even if the trigger is recognized and ushered into the box, its life span is short. An expiration date is imprinted into it. In the sliver of time before it dies, the trigger has one purpose: to be the bright, sparkly thing, the attention-getter that coaxes TV viewers to point the remote at it, push the button and initiate a tryst.

Like salmon, triggers are born with a mission: To make a difficult journey, perhaps with a tryst near the end. If they're lucky. Then it's over. (And we haven't even gotten to the upstream part yet.)

Yet the interactive trigger, for dozens of interactive-service providers, is the capstone in the bridge between today's broadcast world and tomorrow's interactive, session-based world.

Regulators are also curious about triggers-especially who may or may not block them. Fears are already mounting about the potential to slip unauthorized triggers into a broadcast, prior to established business arrangements.

What on earth is a trigger?

The word itself is comes from the Advanced Television Enhancement Forum, or "ATVEF," an ITV standards group spawned by Microsoft Corp., Intel Corp. and others. The idea was to bind interactivity into a TV broadcast. (Some now call this "program synchronous" interactivity.) The design goal was to make it quick and easy-and write once/run everywhere-for content developers.

Quick and easy usually means using existing standards, which in ATVEF's case is HyperText Markup Language, or HTML. The "trigger" is the Web address at which an interactive application is held. Because Internet pages look smeary on TV without some tweaking, the URL embedded in the trigger is usually a special destination, already tweaked for TV resolution.

Triggers ride shotgun, and in real time, within the vertical blanking interval of an analog TV broadcast. In digital broadcasts, like those based on MPEG-2 (Moving Picture Expert Group), triggers splice into a private data stream. Those regions also hold things like closed-captioning information.

In some cases, the TV picture-and any embedded triggers-blast up to a satellite in space, then down to headend receivers on Earth. There, the trigger may be removed and respliced into the picture before riding in one of three signal paths-VBI, in-band or out-of-band-over cable's hybrid fiber-coax plant to a set-top box.

Say the set-top can recognize the trigger. Say it knows to translate it into an eye-catching icon, on the TV screen. Maybe it's an offer for a sample of the "Super-Hot" compost activator Roger Swain is using on Victory Garden. (The writer gets to pick the example.)

Say the viewer decides her own pile could use a kick, and clicks.

What happens next depends on the set-top. Units equipped with a two-way Internet-protocol path (such as an embedded cable modem) would likely fling the request up the cable reverse path, using the IP signal path, through the companion CMTS (Cable Modem Termination System-the headend part of high-speed Internet systems). Destination, out of the CMTS: the server holding the Web link.

Maybe that server is in the headend; maybe it's on another continent. Latency matters here, so that's a good thing to ask when talking to ITV suppliers. The viewer just acted impulsively while watching a show. For her, its about the show, not the impulse. The second it becomes about the impulse, it becomes annoying.

Set-tops that aren't equipped with a two-way IP path have a tougher time with triggers. If the box is a two-way unit with impulse pay-per-view (IPPV) features, it can pass the trigger along-in due time.

Most IPPV boxes rely on a polling technique orchestrated at the headend. Essentially, a companion unit in the headend pings each set-top, one by one, in a big circle. If it were a conversation, it would go like this: Headend to box: "Got anything? No? OK, catch ya next time."

And so on, box by box.

The round-trip is measured in hours, not seconds.

Why should you care about triggers, especially with everyone saying 2001 is VOD's year, with all the interactive stuff to follow?

Two reasons, really: First, it never hurts to understand how things work. Second, triggers are likely to find their way into your system at some point.

If you want to be trigger happy, be sure to ask ITV suppliers about the back channel. Does it require a two-way IP path to a server? (If so, do you have one?) Is the server local or remote? Is there anything proprietary in the mix?

Remember scale, too: What happens if zillions of people all click at the same time? Ask about latency. How long does it take from click to response? Also ask how the service maps onto your existing and future digital set-top deployments.

Triggers do work, by the way. Ask Mixed Signals Technologies or RespondTV, two of several providers that use triggers regularly on the WebTV service.

Whether or not they work for you depends on your technology road map.