Dolby Laboratories Multichannel Audio Tool DP570 - Manual (Page 116)

100 Dolby ® DP570 Multichannel Audio Tool User’s Manual
A Guide to Dolby Metadata
ATSC document A/52. The revised definitions allow more information to be carried about
the audio program and also allow more choices for stereo downmixing. When the
metadata parameters carried in Dolby Digital were first described, they were generically
called bitstream information, or BSI. We refer to the additional parameter definitions as
extended BSI.
Because the revised definitions affect metadata parameters that were not used by the
consumer decoders, all decoders will be compatible with the revised bitstream. Newer
decoders that are programmed to detect and decode the new parameters will be able to
implement the new features Extended BSI provides.
Products that allow emulation of the effects of metadata, such as the DP570, normally have
a feature that allows emulation of a new (or compliant) decoder or a legacy decoder.
D.7.1 Preferred Stereo Downmix Mode
This parameter allows the producer to select either the Lt/Rt or the Lo/Ro downmix in a
consumer decoder that has stereo outputs. Consumer receivers are able to override this
selection, but this parameter provides the opportunity for a 5.1‐channel soundtrack to play
in Lo/Ro mode without user intervention. This is especially useful on music material.
D.7.2 Lt/Rt Center Downmix Level
This parameter indicates the level shift applied to the Center channel when adding to the
Left and Right outputs as a result of downmixing to an Lt/Rt output. Its operation is similar
to the Center downmix level in the universal metadata.
Table D-21 Preferred Stereo Downmix Mode Settings
Preferred Stereo Downmix
Mode
Not Indicated
Lt/Rt Preferred
Lo/Ro Preferred
Table D-22 Lt/Rt Center Downmix Level Settings
Lt/Rt Center Downmix
Level
1.414 (+3.0 dB)
1.189 (+1.5 dB)
1.000 (0.0 dB)
0.841 (–1.5 dB)
0.707 (–3.0 dB)
0.595 (–4.5 dB)
0.500 (–6.0 dB)
0.000 (–999 dB)