Linear Acoustic Technical Note

Linear Acoustic Technical Note

EAS and local emergency audio management in AERO.100/1000/2000 v3

Date: 4/1/15

This Technical Note describes the requirements and configuration of the AERO.100/1000/2000 to

provide both EAS AND local emergency audio insertion in an AERO.100/1000/2000unit.

Background

New rules for TV broadcasters concerning local emergency information are coming in 2015. When

crawls or text containing emergency information are presented on the main broadcast channel the

audio equivalent of these messages must be carried on the station’s SAP channel. (The exception here is

when this information is part of the audio program of a news broadcast). Whether this audio is created

using text to speech engine or by some other means, the broadcaster needs a way to insert this audio

information in place of SAP audio programming. In addition, an alert tone must be broadcast on both

the main and SAP channels to let the audience know that local emergency audio information will be

broadcast on the SAP channel.

Solution

An update for the Linear Acoustic AERO.100/1000/2000 loudness controllers provides several new

options for inserting EAS audio and local emergency audio into the program audio channels, and will

allow many users to meet the new requirements using their existing hardware. These features are

contained in Software version 3.14.24 and Firmware version …0039. Users should contact their factory

representative, or Linear Acoustic dealer, for more information about this free update.

The new software includes SAP handling features on the Pgm 2 DRC (Input 7/8) that are similar to the

features that have always been available on the Local DRC (9/10) input. These include:

• The ability to choose the left or right channel of the SAP as the source for dual mono

• Automatically replace SAP audio with a downmix of the main channel if SAP is not present.

EAS tests and activations and emergency audio alert tones should be played on the main and SAP

channels. In the AERO this can only be accomplished by using the same audio input to the AERO for

both EAS and the local emergency alert tones.

There are several use cases outlined below.

1. If EAS audio is currently input to the AERO Local processor through an AES input then a GPI

controlled 2 x 1 AES digital audio switch could be used, in front of the AERO, to select between

EAS information and local audio alert tones. The same GPO trigger that enables EAS in the AERO

could also switch the AES source to EAS and trigger the AERO to replace main and SAP programs

with the EAS audio. The GPO that signals emergency alert tones could be used to switch the

AES source to the local emergency alert tones and trigger the AERO to override main and SAP

Linear Acoustic Tech Note 4/1/15 Page 2 of 15

© 2015 Linear Acoustic Inc. The Telos Alliance. All Rights Reserved L15/18091

audio programs. In this case ‘override’ means duck program audio and add alert tones to the

audio program channels.

2. If the broadcaster currently embeds EAS audio, into an unused pair in the SDI signal, ahead of

the AERO and uses the AERO Local processor to replace main and SAP audio then local

emergency alert tones must be embedded, in place of the EAS audio, ahead of the AERO. EAS

can use an AERO GPI to replace main and SAP audio programs with EAS. When local emergency

tones are played a different AERO GPI can be used to override main and SAP audio programs as

described above in use Case 1.

3. If the broadcaster currently inserts EAS audio into the main and SAP channels ahead of the

AERO (EAS audio insertion is accomplished entirely outside of the AERO) then local emergency

alert tones can be inserted in the main and SAP audio programs in the AERO. In addition the

local emergency audio (text to speech), or other audio content, can also be inserted in the SAP

channel entirely inside the AERO. Two processing instances are required in the AERO to

accomplish this.

In all cases it is up to the broadcaster to decide how to switch the correct audio input (EAS or local

emergency audio) to the AERO inputs and to trigger the appropriate AERO GPIs for these audio events.

Please read this Technical Note carefully to evaluate the suitability of these solutions to your specific

needs. You are welcome to call your Linear Acoustic representative or dealer if you have questions or

would like assistance configuring your AERO loudness control to meet your particular needs.

A block diagram is included on page 15.



Case 1. Handling both EAS and local emergency audio in the AERO.100/1000/2000

In order to handle both EAS and emergency audio using the AERO processor, two processing Instances

are required. A second instance (5.1 or 2.0) can be added to any AERO.100/1000/2000 if you do not

already have two instances in your unit. The upgrade to add a second instance to an

AERO.100/1000/2000 is done with a license code added by the user in the field. If you are interested

please contact your Linear Acoustic dealer or factory representative for more information and pricing.

The configuration below is for an AERO.100/1000/2000 with two instances. The examples show

Instance 1 as 5.1 and Instance 2 as 2.0.

It is assumed that:

1. The broadcaster intends to put EAS audio and local emergency alert tones on both the main and

SAP audio programs and

2. Local emergency audio content will go only to the SAP channel.

3. Local emergency audio alert tones and EAS audio are both inserted into the same audio input

(SDI embedded or AES digital audio input) upstream of the AERO.

In this example configuration Instance 1, the 5.1 Instance, does the following:

• Loudness control of the main audio program, (and upmixes to 5.1 if desired))

• Produces a fulltime downmix that can be assigned to the Instance 1, Proc 9/10 output.

• Replaces main program and SAP audio with EAS audio

• Overrides and ducks main and SAP programs with local emergency alert tones

• Accepts loudness controlled SAP program from Instance 2

The second instance, Instance 2, does the following:

• Creates downmix of the main program audio for automatic SAP replacement if desired.

• Creates the SAP program from one or both channels of the incoming SAP pair

• Can output a full time main program downmix from Instance 2, Proc Out 9/10

• Replaces SAP with local emergency audio.

Instance 1 Configuration Using GPI control

In this example the main program configuration has surround sources on inputs 1/2, 3/4, and 5/6 of

Instance 1. Stereo sources appear on pair 1/2. EAS audio is connected to AES Input 1/2 input and is

routed to Local DRC, Input 9/10. The SAP output of Instance 2 is connected to AES Input 5/6 and is

routed to Pgm 2 DRC, Input 7/8.

Note: EAS and local emergency audio can be brought in on any AES digital audio input or embedded on

any incoming SDI pair. The routing capability of the AERO allows any AES input or SDI embedded source

to be applied to any processing instance input.



The routing of sources to Instance 1 inputs is shown in Figure 1 below.

Figure 1

SAP audio (from Instance 2) is looped from the AES 5/6 output BNC to the AES 5/6 input BNC on the rear

panel. As seen in Capture 1 (above), Input 7/8= AES 5/6. Pgm 2 uses Output 7/8. Please take note of

all of the settings in Figure 2 for Output 7/8, below.

Figure 2



Pgm 2, Output 7/8, is configured for stereo in and the output mode is normal. DRC Program 2 should be

put in bypass:

Instance 1 > DRC Program 2 >Bypass and set bypass On.

This is done because the loudness control for SAP and local emergency audio is done in Instance 2.

Instance 1 is simply used to override SAP with EAS audio or local emergency alert tones when required.

EAS audio or local alert tones are routed to Input 9/10. (The user must provide switching between EAS

audio and local emergency alert tones ahead of the AERO input.) DRC Local uses Output 9/10 and this

must be set to Local mode. Local Audio Override is set to Off for GPI control. Destination: Program 1 + 2

configures EAS audio on the Local program, Input 9/10, to override both main and SAP channel audio.

See Figure 3, below.

Figure 3

In the Output 9/10 configuration Downmix -> 9/10 is set to On. The 9/10 output can have a full time

downmix while the Local DRC remains ready to override Pgm 1 + Pgm 2 with EAS audio.

The downmix parameters can be set to the user’s preference. The Downmix Gain can be set to trim the

downmix output level as desired.

The configuration for Output 9/10 is shown in Figure 4, below.



Figure 4

Instance 2 Configuration Using GPI control

The next step is to configure Instance 2 for SAP and local emergency audio override of SAP.

The main program audio is selected as the source for Instance 2, Pgm 1 DRC. Inputs 1/2, 3/4, 5/6 are

used to create a main channel downmix source for SAP when SAP audio is not available.

The SAP program is sent to DRC Pgm 2 (Input 7/8). In this example the source of the SAP program is SDI

7/8.

Finally, a source for the local emergency audio is chosen. In this example AES 3/4 is used. AES 3/4 is

selected as the source for Instance 2, Local DRC, Input 9/10.

Note: The source of local emergency audio, or SAP audio, can be any AES digital audio input or SDI

embedded pair.

Instance 2 source configuration is shown in Figure 5, below.



Figure 5

Next is the configuration for the SAP on Instance 2, Pgm 2 DRC (Output 7/8).

Figure 6

7/8 Input Source is set to 7 Only so that the SAP audio is taken from the left channel of the SAP pair.

This conforms to the standard used by NBC, ABC and others.



The 7/8 Output Mode is set to Auto Downmix so that a downmix replaces SAP when SAP is not available.

The Auto Dmx Holdoff (automatic downmix holdoff) is set to 4 seconds. This is to prevent the main

channel from interrupting SAP when there is simply a pause in SAP audio and not an end to the SAP

program. This value can be changed to any suitable value.

The configuration for the Instance 2, Local DRC (input 9/10) is shown in Figure 7, below.

Figure 7

The 9/10 Input Mode:Local means the 9/10 input will override Pgm 1 or Pgm 2 according to the

Destination setting.

Local Audio Override: Off sets normal operation as no override. It allows control by GPI or network

command.

Destination: Program 2 sets the SAP program as the one to be replaced by the local emergency audio.

The Instance 2, Output 9/10 configuration options have no effect on the configuration described here.

The SAP output of Instance 2 is assigned to AES 5/6 digital audio output of the AERO in this example.

Output Routing > AES/SDI Outputs > AES Outputs > AES Out 5/6: Instance 2 Processed 7/8

GPI Configuration

GPIs must be disabled to change GPI settings. System > GPI > GPI



Three GPIs are required for this configuration. The first is for EAS activation in Instance 1. It requires a

pull to ground (or dry relay closure) for the duration of the EAS audio. This closure will replace audio on

both the main and SAP outputs with EAS audio.

A second closure is required to duck the main and SAP program audio and override it with the local

emergency alert tones.

A third closure is required for local emergency audio to replace the SAP audio in Instance 2. This closure

will also require a pull to ground (or dry relay closure) for the duration of the local emergency audio

message.

The configuration is shown in Figure 8, below:

Figure 8

In the configuration shown GPI A causes EAS audio to replace main and SAP audio outputs in Instance 1.

GPI B causes local emergency alert tones to duck Main and SAP and override them in Instance 1.

GPI C causes local emergency audio to replace the SAP channel only in Instance 2.

Please note that local emergency alert tones must replace the EAS receiver/generator audio on Instance

1 Proc Input 9/10 UPSTREAM of the AERO. A 2 x 1 AES switch with GPI control could be controlled using

the same GPO outputs that control the EAS and emergency alert tone GPIs in the AERO.



Coax Jumper and Delay Settings

A coax jumper must be connected from AES Output 5/6 to AES Input 5/6 on the AERO back panel. The

SAP audio from Instance 2 (AES 5/6 Out) is re-entering the AERO (AES 5/6 In) and is used as the SAP

source to Instance 1. This input to Instance 1 has SAP with emergency audio already applied. EAS audio

replaces the SAP channel whenever there is an EAS activation. Local emergency alert tones will duck

main and SAP audio and override them. EAS will take precedence over local emergency audio.

The delay on the SAP program audio will be longer than the delay of the main program and the downmix

outputs of Instance 1. This is because the SAP audio passes through two Instances. The additional

delay, or latency, can be corrected for using the AERO audio and video delay settings.

The delay values for Dolby Digital encoding in the new software (v 3.14.24) are different than the delay

values in previous versions. The new software supports Dolby Digital and Dolby Digital Plus+ and has a

latency of 64 ms. Previous versions of software supported only Dolby Digital encoding and had a latency

of 32 ms.

Two configurations are given below. The first is for an AERO that does not do any Dolby encoding. The

second system has Dolby encoding on the main program channel. Note that Dolby E encoding has

additional latency. Please contact your Linear Acoustic representative if you need assistance with

configuring Dolby E in your AERO.

Note: A configuration that handles both EAS insertion and local emergency audio insertion in SAP cannot

Dolby encode the SAP channel.

The recommended starting values with no Dolby Digital or DD+ encoding are:

System > I/O Setup > Video Delay > SDI Video Delay: 358 ms

Instance 1 > Output > Output Delay > Output Delay 1/2: 179 ms





If Dolby encoding is used for the main channel output (Instance 1, Pgm 1, Outputs 1-6) the delay values

are as follows:

System > I/O Setup > Video Delay > SDI Video Delay: 358 ms








Instance 1 > Output > Output Delay > Dolby Encoder Delay: 115 ms

The second set of values includes Dolby encoding of the main channel. The delay of the Dolby encoded

output is increased to match the latency of the SAP program. This puts each of the audio program

outputs: main, SAP, and downmix, in sync with the Dolby encoded output. If the main, SAP or downmix

program outputs are embedded in the SDI stream or taken as AES outputs from the AERO the delay

settings ensure that video, Dolby encoded audio and LPCM audio will all be in sync.

Operation of this Configuration.

The main audio program is input to Instance 1, Pgm 1 DRC on inputs 1-6. SAP audio (from Instance 2) is

input to Instance 1, Pgm 2 (Input 7/8). EAS audio is input to Instance 1, Local DRC (Input 9/10). A

downmix of the main channel appears at Output 9/10. When an EAS test, or activation, pulls GPI A to

ground then the EAS audio overrides both the Pgm 1 (main) and Pgm 2 (SAP) outputs.

The main audio program is also input to Instance 2, Pgm 1, inputs 1-6. The SAP program is input to

Instance 2, Pgm 2 (Input 7/8). The Local Emergency Audio is input to Instance 2, Local (Input 9/10).

If SAP audio is not present a downmix of the main program will automatically replace the SAP audio.

When a local emergency audio message activates GPI B then the SAP audio is replaced by the local

emergency audio.

The SAP output from Instance 2, Prg 2 DRC 7/8 is routed out of the AES 5/6 output and re-enters

Instance 1 through AES 5/6 input. The SAP is the input to Instance 1, Pgm 2. In this way EAS messages,

can override SAP.

Control using http commands over the network.

EAS and emergency audio override can also be controlled by network commands.

To turn On EAS override of main and SAP in Instance 1:

http://192.168.1.11:7380/parameter/inst_1/out/local_state=3

To turn Off EAS override of main and SAP in Instance 1:


To turn On local emergency audio override of SAP in Instance 2:




To turn Off local emergency audio override of SAP in Instance 2:


Control using automatic (audio presence) EAS and local emergency activation

The presence of audio can automatically trigger the override of main and SAP audio in Instance 1. Any

audio on the Local input, (Proc Input 9/10) that is above -60 dBFS will cause the override of main and

SAP. Likewise the presence of local emergency audio can automatically trigger the override of SAP

audio in Instance 2. Any audio on the local emergency audio input above -60 dBFS will cause the

override of SAP.

For override to be automatic the Local mode must be changed to Vox, voice activation. This is done on

the Instance 1 > Output > Local menu and the Instance 2 > Output > Local screens.

The Vox configuration for Instance 1 is shown in Figure 9, below.

Figure 9



The Vox configuration for Instance 2 is shown below in Figure10

Figure 10

Remember that any audio on a Local Input set for Vox mode that is higher in level than -60dBFS, will

automatically override the program audio.

Case 2. EAS and local emergency alert tones embedded in SDI input.

The configuration for Case 2 is identical to Case 1 except that the source of the Instance 1, Local Input,

(Proc Input 9/10) is the SDI embedded pair where EAS and the local emergency alert tones appear.

In the first example EAS and local emergency alert tones were connected to AERO AES Input 1/2. EAS

audio or the local emergency alert tones were externally switched to the AES 1/2 input.

In this case the user will embed EAS audio, or local emergency alert tones, on the same embedded audio

pair ahead of the AERO. With the exception of the source selection for Instance 1, Local Input (Proc In

9/10) = SDI x/y everything else in the configuration is the same.

Case 3. EAS audio insertion is accomplished entirely external to the AERO.

The configuration for Case 3 is, again, identical to Case 1 except that the source of the Instance 1, Local

Input, (Proc Input 9/10) is the AES input pair that the local emergency alert tones appear on. If the alert

tones and local emergency audio appear on the same AES input then the same input is chosen for

Instance 1 and Instance 2 Local Inputs. If the local emergency alert tones are a separate audio source

than the local emergency audio then select an unused AES input and use this as the source for Instance

1 Local Input.



As in the other two cases one GPI is used to duck and override main and SAP audio programs with the

alert tones in Instance 1. A second GPI is used to replace SAP audio with local emergency audio in

Instance 2.

Remember to SAVE the Configuration!

In Nf Remote go to:

System > System > Backup to save the configuration to your PC or laptop.

Linear Acoustic Tech Note 4/1

Acoustic Tech Note 4/1

© 2015 Linear Acoustic Inc. The Telos Alliance. All Rights Reserved

Acoustic Tech Note 4/1/15



© 2015 Linear Acoustic Inc. The Telos Alliance. All Rights Reserved© 2015 Linear Acoustic Inc. The Telos Alliance. All Rights Reserved© 2015 Linear Acoustic Inc. The Telos Alliance. All Rights Reserved L15/18091

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