The View From 2009: This is a brief intro and discussion of Dolby’s metadata set used in set-top boxes in the U.S. It’s still interesting, and still confusing.

Ah Never Met A Data Ah Didn’t Like, Will Said

Metadata! Comin’ at ya!

We’ll take a break from bad audio concerns this month, to take a look at one of the most fascinating audio issues/processes/ideas to come up in the past 25 years. That issue/process/idea is called, aptly enough, metadata.

Now, the prefix “meta” means, among other things, “beyond, transcending, more comprehensive.” So, using that idea, metadata is data that transcends data. Metadata is data about data, or, in this case, data about our beloved audio signal.

The lure of this has been around ever since there were two radio stations and two listeners. The problem is actually a simple one: different broadcasters have different ways of doing things, and when we switch our observation back and forth between two such broadcasters, we tend to get annoyed by the fact that they are, well, different, and that we have to readjust our receiver each time we switch.

At the same time, broadcasters would like to know with reasonable confidence the level at which the consumer is listening. And after they think about it, well, they realize they would actually like to control, sort of, that consumer playback level.

Somewhere along the line, the idea was probably first expressed around some test bench as, “Wouldn’t it be great if we could fit all radios and TVs with remote volume controls so we could adjust the playback levels as part of signal transmission? That’d be really cool, solve a lot of problems. Yeah!”

Three goodnesses accrue. First, we can account for differences in level between programs, so that the poor consumer doesn’t have to keep adjusting the volume each time he or she changes channels, and second, we can set the volume for an appropriate level for a given program, so that when NASCAR comes on, WE can make the appropriate adjustments (whatever THEY are). Leave the consumer out of it, just get the levels right, once and for all. Sweet!

The third goodness, the really important one, is that we can “adapt” the signal for different end-users’ environments, so that metadata will work differently depending on the end-users set-up. This, of course, requires knowledge of the range of end-user setups and needs. It suggests a certain modicum of communication between the end-user, or at least the end-user’s system, and the broadcaster.

In my work with surround sound, all kinds of similar meta-ideas have come up over the years. Like, the producer could dial in the amount of delay she wants for the surround channels for any given piece, even dynamically. Or, she could specify that the Center Channel should be an overhead channel for this particular recording, if the consumer has an overhead available. Cool ideas!

But the basic gist of it is this: we sell “smart” receivers, and then we include as part of the signal we broadcast, control data that operates those smart receivers, so we can optimize them for our broadcast purposes. That control data is what we call “metadata.” You know all this, right?

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