Grass Valley DAP-1781 - Manual (Page 46)

GUIDE TO INSTALLATION AND OPERATION
46 | DAP-1781
4.6.3 UPMIX/DOWNMIX – DOWNMIX tab
This tab provides resources to control the downmix of a
“5.1 channel” surround-sound audio signal into an LtRt
or LoRo stereo pair. The 5.1 terminology refers to six
discrete audio channels, with the low-frequency channel
of limited bandwidth designated as the .1 channel. The
downmix can be done using any of the 16 audio
channels processed by the audio processor using the
Input Channels controls in the interface.
Input Channels: The default source channels are
CH1 to CH6, but the input shuffler allows any
combination of the input channels.
Downmix:
Operation Mode: Use the pull-down to select the
downmix operating mode:
• Manual: Downmix follows the downmix
parameters manually configured by the user.
• Follow Metadata: Downmix follows the
downmix parameters of the Metadata.
Level Normalization: use the pull-down to select the
type of normalization to be applied on the downmix
output level.
•
OFF: Downmix output level is not normalized. Clipping may occur depending on the input
channel levels and the selected mix levels.
•
Level A: Downmix output level is normalized based on the applied mix levels to provide a
uniform output over the range of mix levels available. Clipping will never occur, even with full
scale input channels and mix levels.
•
Level B: Downmix output level is normalized based on the channel configuration to provide a
uniform output loudness between 3/2 and other programs (2/0, 3/0, 2/1, 3/1, 2/2). For example,
downmixing a 3/2 program produces a loudness attenuation compared to the same program in
2/0 at the same input loudness. To provide a uniform output loudness, a loudness attenuation
is applied on all programs except 3/2. If the operating mode is Follow Metadata, the channel
configuration is given by the AC-3 coding mode parameter in the metadata. If the operating
mode is Manual, the channel configuration is given by the selected mix levels.
Table 2: Channel Configuration in Manual Mode
Center Mix
Level
Surround Mix
Level
Channel
Configuration
mute mute 2/0
not mute mute 3/0
mute not mute 2/2
not mute not mute 3/2
Level-B normalization also includes Level-A normalization, based on the applied mix levels.
Clipping will never occur, even with full scale input channels and mix levels.
Output Channels: The downmixed stereo pair is mapped into the channel pair selected in the pull-down
menu
Reversion Mode: Used only when Operation Mode is set to Follow Metadata. It determines which
downmixing configuration to revert to when there is no valid Primary (external input) Metadata. Downmixing