Technical data

DOC-01-TELAS-CRG-4 ASTi ACE Studio Components Reference Guide Rev.M
124 Copyright © 2014 Advanced Simulation Technology inc.
8.0. Highway Service
Summary: The highway service provides audio distribution for aural cues from
components in ACE to the outside world. The need for a specialized service to
handle aural cue audio is driven by the fact that aural cues are generated by multiple
sources whose output is typically sent to multiple channels (e.g. left speaker, right
speaker). The highway service handles both the mixing of audio from multiple
sources and the routing of the composite audio to multiple channels.
The highway service supports 12 independent output channels. The service
receives audio from a set of Balancer components. Each Balancer component sends
a stream of audio to the service with applied gains for the audio on each of the 12
highways. The service mixes the audio sources for a given highway to create a
composite audio stream for each highway. The service applies highway gains that it
receives from a HighwayGain component. This set of gains includes an overall
output gain that affects all highways and individual highway gains that affect all
audio on a given highway. The service sends the composite audio to a
HighwayOutput component, which is tuned to one and only one highway. The
highway service supports input connections from only the Balancer and
HighwayGain components and output connections to only the HighwayOutput
component.
As with all service components, the user does not manually instigate the creation of
the service object. Instead, this is done automatically on demand by the loader
when it detects that a component has a highway service port connection. Only one
highway service component will be loaded in a model based on the first found need
for a service of this type.
Description: The Highway Service component receives an audio input and an array
of 12 gain values (one for each highway) from each balancer component. The
highway service can connect to up to 1024 balancers. The connection from the
balancer to the highway service is unidirectional for audio data. The balancer is
always the audio source while the highway service is always the audio sink.
For each balancer connection, the highway service effectively makes 12 copies of
the audio and applies a different gain value to each copy. The gain values come
from the gain value array provided by the balancer. The output from this step is a
set of 12 audio streams (one for each highway) per balancer.
The highway service mixes the audio from the various balancers for a given
highway into a final audio output for that highway.
The highway service also receives an input connection from the HighwayGain
component, which provides an overall output gain and twelve individual highway
gains. The highway service applies the gains it receives from the HighwayGain
component to the composite audio on each highway. Each model may contain only
one HighwayGain component. The model loader should throw an error if a user
attempts to add a second HighwayGain component. If there is no HighwayGain
component in the model, the highway service should use a value of 1.0 for these
gains.
The output connection from the highway service goes to a HighwayOutput
component. This output connection is unidirectional for audio data. The highway
service is always the audio source while the HighwayOutput is always the audio
sink. Multiple HighwayOutput components may point to the same highway
channel.
The service must also support the flow through of Active_TX flags to indicate the
state of audio activity on a highway. The Active_TX flag should be set only if there
is audio present and a non-zero gain value at a given point in the path.
The Highway Service tool will also support diagnostic facilities to allow the user to
view the use of a highway within the model and the current highway gain settings.
This will scan the model for all HighwayOutputs the HighwayGain and extract the
information into a table-like view as demonstrated in the following example:
Handle view – this will display all HighwayOutputs including their paths that are
connected to each handle as well as the gains associated with each highway (Note:
This is just an example to show the type of information to be displayed.):
Overall Output Gain = 1.0
Left_Speaker (Gain = 0.5) --->
Aural_Cues / Left_Speaker_Sounds > HighwayOutput_A
Aural_Cues / Left_Speaker_Sounds > HighwayOutput_B
Seat_Shaker (Gain = 0.8) --->
Some_Folder1 / Some_Folder2 / Vibration_Output > HighwayOutput_C