Translation Please

Interactive TV And Pipe Cleaners

4/19/2010 1:50 PM

Almost 10 years ago, this column investigated the fraught-ridden life of the interactive-TV trigger and its taxing journey from origination to TV screen.

“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,” the column noted.

Back then, we were talking about ITV triggers in terms of “ATVEF” (pronounced as a word), the name of a Microsoft- originated standard at the time. (And you thought “EBIF” was bad.)

Then and now, “triggers” are the clickable things that appear on the TV screen, hoping to be bright and sparkly enough to entice viewers to click.

This was back in the days when interactive TV triggers slipped into the vertical blanking interval of analog TV signals - the place where closed-captioning data rode. Digital ITV was still fairly new.

Then and now, the matter of trigger transit safety is huge. So much so that these days, in the engine rooms of interactive TV and EBIF, you hear people talking about “pipe cleaners.”

EBIF stands for Enhanced TV Binary Interchange Format. Just the inclusion of the word “binary” should be an indicator that it’s teeny - written tightly, on purpose, so as to reach as many fielded set-top boxes as possible (25 million this year, of a total potential footprint of 50 million-plus).

But just because EBIF apps are small (about 150 Kilobits per second, rough numbers) doesn’t mean they’re any less vexed by transit issues. Think about it: Being the clickable thing on the screen means being squirted into a video bit stream, blasted up into geosynchronous orbit (or injected into a terrestrial fiber backbone), received, processed and resent to homes.

The “pipe cleaner” talk, then, is about how to keep that whole transit path clear of debris and drop points.

Technically, pipe-cleaning is a workflow. It involves plunking a data feed on top of a video stream’s primary audio and video packet identifiers, or PIDs, at the content origination point. (For the advanced class, this involves the use of a special scheduler, which talks to a special data carousel to create an additional MPEG Transport Stream containing EISS and DSM-CC PIDs.)

Without pipe-cleaning, triggers run the risk of getting squished or dropped somewhere along the way, which means they don’t get to the TV screen. Not good.

Key places to start jabbing the pipe cleaner, if you’re the one in charge of degunking: Satellite receivers with analog outputs, certain re-encoding points, and in those dense quadrature amplitude modulation multiplexes.

June