Dolby Laboratories DP564 - Manual (Page 72)

DP564 Multichannel Audio Decoder Appendix A: Metadata
A-2
decoder processes the metadata stream according to parameters set by the program
creator, as well as certain settings for bass management and dynamic range that are
chosen by the consumer to reflect their specific home theater equipment and
environmental conditions.
Dolby E is a distribution bitstream capable of carrying up to eight channels of
encoded audio and metadata. The number of programs ranges from one single
program (Program Config: 5.1) to eight individual programs on a single Dolby E
stream (Program Config: 8
× 1). Each program is discrete with its own metadata in
the Dolby E stream. Some control metadata parameters in a Dolby E stream
automatically configure a Dolby Digital encoder while others are passed through to
the consumer’s Dolby Digital decoder.
Dolby E is a professional technology used for broadcast applications such as program
origination and distribution; the Dolby E bitstream carries the entire metadata
parameter set. Dolby Digital, used for consumer applications such as transmission to
the home or for DVD authoring, employs a subset of the entire metadata parameter
set called Dolby Digital metadata; the Dolby Digital bitstream carries only those
parameters necessary for proper decoding by the consumer.
Metadata is first inserted during program creation or mastering, and is carried through
transmission in a broadcast application or directly onto a DVD. The metadata
provides control over how the encoded bitstream is treated at each step on the way to
the consumer’s decoder.
For example:
In a broadcast truck parked outside a football stadium, the program mixer chooses the
appropriate metadata for the audio program being created. The resulting audio
program, together with metadata, is encoded as Dolby E and sent to the television
station via fiber, microwave, or other transmission link. At the receiving end of this
transmission, the Dolby E stream is decoded back to baseband audio and metadata.
The audio program is monitored and the metadata is altered or re-created as other
elements of the program are added in preparation for broadcast. This new audio
program/metadata pair is re-encoded as Dolby E, leaves the postproduction studio and
is passed through the television station to Master Control, where many incoming
Dolby E streams are once again decoded back to their individual baseband digital
audio/metadata programs. The audio program/metadata pair that is selected to air is
sent to the transmission Dolby Digital encoder, which encodes the incoming audio
program according to the metadata stream associated with it, thereby simplifying the
transmission process. Finally, the Dolby Digital signal is decoded in the consumer’s
home, with metadata providing the information for that decoding process. Through
the use of metadata, the mixer in the truck has been able to control the home decoder
for the sporting event, while news breaks, commercials, station IDs, and the like are
similarly appropriately decoded.
This control, however, requires the producer to correctly set the metadata parameters
because they affect important aspects of the audio—and can seriously compromise
the final product if set improperly. Although most metadata parameters are