Specifications

Standards and Practices for Authoring Dolby
®
Digital and Dolby E Bitstreams
9
channels and adds them in phase to the left channel and out of phase to the right
channel. This allows a Dolby Surround Pro Logic decoder to reconstruct the L/C/R/S
channels for a Pro Logic home theater. The Lo/Ro downmix adds the left and right
surround channels discretely to the left and right speaker channels. This preserves the
stereo separation for stereo-only monitoring and provides a mono-compatible signal.
The LFE channel is not included in either of these downmixes.
On most equipment, the consumer can, through the product’s user interface, choose
the appropriate downmix for their playback system. Certain metadata parameters
allow the engineer to select how the stereo downmix is constructed and which
downmix is preferred, although the Lt/Rt downmix is usually the default.
As previously mentioned, user adjustment of Dynamic Range Control (DRC) is
limited while downmixing; the use of the stereo analog outputs of DVD players, set-
top boxes, and game consoles are no different. Typically, the consumer is not able to
adjust the cut or boost parameters when using the stereo outputs and the only DRC
available is the selection of a “Midnight Mode” or the equivalent.
Some metadata parameters assist in achieving an appropriate downmix, helping to ensure
that the intention of the engineer/content producer translates correctly across these
environments. Specifically, metadata provides control over how certain channels are
“folded” into the resulting downmix. As with DRC, downmixing is ultimately the choice
of the consumer and dependent upon their unique listening environment.
While the engineer is tasked with optimizing the multichannel mix for reproduction in
an ideal monitoring environment, it is important to reference the mix in downmixing
conditions to ensure cross-platform compatibility and the proper selection of the
downmixing metadata parameters. The many different consumer listening modes can
be heard through front-panel selections on either the DP562 Reference Decoder or the
DP570 Multichannel Audio Tool.