Metadata only get used if they provide clear advantages without downsides. When benefits are not
obvious, the extra work and equipment needed to create metadata, the extra latency, and the potential compatibility issues they will pose over time, work against the concept. Its no wonder why
broadcasters are seeking more effective methods to control loudness than basing a station on part
of a solution for just one platform.
To use AC3 metadata as the main level and range control, actually has further downsides. It is
unpredictable how a consumer has his/her receiver set up, and the reproduction level can become a
mess when metadata is missing or wrong. Acknowledging these problems, Dolby has introduced a
loudness control solution, Dolby Volume, for manufacturers of consumer equipment. Dolby Volume
is single-ended and doesnt require metadata to function. If its complexity is high enough, it may
completely disregard metadata and not worry about whether they are correct or not.
Single-ended consumer control of loudness has been a long time coming, but should be welcomed.
Apples relatively simple solution in iTunes was among the first to offer an answer better than peaklevel normalization to the general public. With Dolby Volume, and other technologies on the horizon,
we can finally hope to rebuke the loudness war in music and film production.
With regard to broadcast, however, intangible consumer processing cannot be relied on. Metadata
is one layer of extra unpredictability; single-ended consumer processing is another. Audio should
therefore be adequately preconditioned at the station, and transmitted with fixed metadata to keep
uncertainties at a minimum. Fortunately, AC3 can work well without stations having to go through
the trouble of using more of its metadata extension than to signal changes between stereo and 5.1.