1
9921-FS Functional Description
1-18
9921-FS PRODUCT MANUAL
9921-FS-OM (V1.18)
Audio Output Routing Function
(See Figure 1-5.) The output routing function provides routing to card
outputs. This function can also direct internal bus signals to further mixing
capabilities or advanced Audio DSP functions. This function also provides
gain and mute controls for each signal.
Audio DSP functions include 5.1-channel and stereo loudness processing, and
upmixing.
Audio DSP Functions Overview.
The Audio DSP block provides the
function complement (selected via user controls) listed below. Because this
block is entirely software-based, it can provide the Audio DSP combinations
listed below (depending on ordered options).
•
5.1-Ch Loudness Pro Dual Stereo Loudness Processors
•
Dual 5.1-Ch Loudness Processors
•
5.1-Ch Loudness Pro Upmixer
•
Dual Stereo Loudness Proc Dual Stereo Loudness Processors
•
Dual Stereo Loudness Proc Upmixer
•
Dual Upmixers
2.0-to-5.1 Upmixer.
The 2.0-to-5.1 upmixer function
receives a normal PCM stereo pair from any internal bus channel pair. The
stereo pair is upmixed to provide 5.1 channels (Left (
L
), Right (
R
), Center (
C
),
Low Frequency Effects (
LFE
), Left Surround (
Ls
), and Right Surround (
Rs
)).
Whenever the upmixer is active, it overwrites the six selected 5.1 output
channels with the new 5.1 upmix signals (including replacing the original
source stereo
L
and
R
inputs with new
L
and
R
signals).
The 2.0-to-5.1 upmixer can be set to upmix in any of three modes: Always
upmix, Bypass upmix, or Auto enable/bypass upmixing. The Auto upmixing
mode looks at the signal levels on the selected channels and compares them to
a selectable level threshold. It then determines whether or not to generate 5.1
upmixing from the stereo pair as follows:
•
If the upmixer detects signal level below a selected threshold on all
three of the selected channels designated as
C
,
Ls
, and
Rs
, this
indicates to the upmixer that these channels are not carrying 5.1. In
this case, the upmixer produces new 5.1 content generated by the
upmixer.
•
If the upmixer detects signal level above a selected threshold on any
of the three selected channels designated as
C
,
Ls
, and
Rs
, this
indicates to the upmixer that the channel(s) are already carrying
viable 5.1 content. In this case, the upmixer is bypassed and the
channels fed to the upmixer pass unaffected to the upmixer outputs.
