Linear Acoustic LA-5448 User manual

Model LA-5448
AC-3 Frame Synchronizer and Rate Shaper
User’s Guide

Model LA-5448
AC-3 Frame Synchronizer and Rate Shaper
User Guide
Release Date: February, 2006
Software Version: 01.00.21 and later
Linear Acoustic Inc.
Phone: [phone]
FAX: [phone]
email: www.LinearAcoustic.com

Warranty Information
DISCLAIMER OF WARRANTIES: Products manufactured by Linear Acoustic Inc. are war-
ranted against defects in material and workmanship for a period of two (2) years from the date
of purchase. THERE ARE NO OTHER IMPLIED OR EXPRESS WARRANTIES AND
NO WARRANTY FOR MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE.
During the warranty period Linear Acoustic Inc. will repair, or at our discretion replace, com-
ponents which prove to be defective, provided the unit is returned, shipped pre-paid to us directly
with a return authorization (RA) number clearly marked on the packaging. Please note, this
RA number must be present or package will be refused and returned to sender.
All requests for repairs MUST include the unit serial number to ensure quick and accurate service.
DEFECTS CAUSED BY UNAUTHORIZED MODIFICATIONS, MISUSE OR ACCI-
DENTS, UNAUTHORIZED CUSTOMER REPAIRS, OR ANY FURTHER DAMAGE
CAUSED BY INADEQUATE PACKAGING FOR SERVICE RETURN ARE NOT COV-
ERED BY THIS WARRANTY.
PLEASE SAVE THE SHIPPING CARTON AND ALL PACKING MATERIALS. FAIL-
URE TO RETURN UNIT IN ORIGINAL SHIPPING CARTON AND PACKING
MATERIALS WILL RESULT IN A CHARGE FOR NEW SHIPPING MATERIALS.
LIMITATION OF PERIOD OF ACTION ON CONTRACT: No action, regardless of form,
arising out of the transactions under this agreement may be brought by buyer, its successors,
agents and/or assigns, more than two years from date of purchase.
LIMITATION OF LIABILITY: It is understood and agreed that Linear Acoustic’s liability
whether in contract, in tort, under any warranty, in negligence or otherwise shall not exceed the
cost of repair or replacement of the defective components and under no circumstances shall
Linear Acoustic be liable for incidental, special, direct, indirect or consequential damages, or loss
of use, revenue or profit even if Linear Acoustic or its agents have been advised, orally or in
writing, of the possibility of such damages.
StreamStacker, upMAX, AutoNorm, metaMAX, CrowdControl and AEROMAX-TV are reg-
istered trademarks of Linear Acoustic Inc., all other trademarks remain the property of their
respective owners.

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide
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Table of Contents
List of Figures..........................................................................................................................................vii
Chapter 1: Introduction...................................................................................................................5
1.1 Principles of Operation..........................................................................................5
1.2 Location of LA-5448..............................................................................................6
1.3 Future Updates........................................................................................................6
1.4 Warranty and Feedback .........................................................................................7
Chapter 2: Connections..................................................................................................................9
2.1 Unpacking and Inspection ....................................................................................9
2.2 Installation ...............................................................................................................9
2.3 Rear Panel ..............................................................................................................10
2.3.1 Connection Ports .................................................................................10
2.4 Quick Setup Notes ...............................................................................................11
Chapter 3: Applications................................................................................................................13
3.1 AC-3 (Dolby Digital) Notes................................................................................15
3.1.1 Output Mode ........................................................................................15
3.1.2 Multiplexer Timing Issues...................................................................15
Chapter 4: Menus..............................................................................................................................17
4.1 Main Menu Level..................................................................................................19
4.1.1 Status Menu...........................................................................................19
4.1.2 Statistics Menu......................................................................................19
4.1.3 Setup Menu ...........................................................................................19
Chapter 5: Troubleshooting.......................................................................................................21
5.1 Problems and Possible Causes............................................................................21
5.1.1 Status Lights are Green, but Display Shows Random Data..........21
5.1.2 Program 4/REF Input LED is Amber.............................................21

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide
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5.1.3 Unit Produces 448 kbps Output, but it is Silent..............................21
Chapter 6: Specifications............................................................................................................23

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide
vii
List of Figures
1-1 LA-5448 Frame Synchronizer/Rate Shaper Block Diagram ........................................................6
2-1 Rear Panel ...........................................................................................................................................10
3-1 LA-5448 processing three individual AC-3 streams, rate shaping disabled ..............................13
3-2 LA-5448 processing three separate streams, rate shaping enabled. ...........................................14

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide
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Chapter 1: Introduction
The Linear Acoustic LA-5448 AC-3 Frame Synchronizer and Rate Shaper accepts
three independent AC-3 streams and synchronizes them to a reference signal applied
to the fourth input. This fourth input will accept 48kHz AES signals containing
PCM or AC-3. If an AC-3 signal is applied, it will also be processed as a fourth pro-
gram, but as it is also reference, it must be a stable 48kHz source (AC-3 data rate does
not matter).
The Linear Acoustic LA-5448 has the following features:
• High density frame synchronization of AC-3 bitstreams
• Silent frame mode replaces errored or missing AC-3 frames with known good
versions
• Rate shape mode allows output data rate to be fixed at 448 kbps while the input
data rate can vary between 96 kbps and 448 kbps
• Features combine to allow artifact free, stable switching of pre-encoded content
(i.e. commercial insertion) while maintaining critical AC-3 parameters
• Dual, redundant power supplies and hard-bypass for mission critical applications.
1.1 Principles of Operation
Figure 1-1 shows the internal audio path of the LA-5448.
It should be noted that this diagram is a general representation of signal flow. Please
consult the appropriate section of this manual for specific functionality.

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide Introduction
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Figure 1-1 LA-5448 Frame Synchronizer/Rate Shaper Block Diagram
1.2 Location of LA-5448
The Linear Acoustic LA-5448 Demultiplexer/Splicer is best located near network
satellite receivers or just prior to a multiplexer. In some cases, it maybe located near
AC-3 encoders such as a Dolby DP-569. As it will likely be in a transmission envi-
ronment, dual redundant power supplies and hard relay bypass are provided for trou-
ble free operation.
1.3 Future Updates
Software updates may become available in the future to add additional features and
performance. Updates will utilize the serial port to accomplish the installation of up-
graded software, and a loader application will be provided for this purpose.
PGM 1
Out
PGM 1
PLL/
Clock
Format &
AES Tx
Format &
AES Tx
Format &
AES Tx
Format &
AES Tx
CPU
(FPUI, I/O, PSU Mon,
System Control)
PGM
2
Out
PGM 3
Out
PGM
4
Out
Delay
Delay
Delay
Delay
Bypass
Bypass
Bypass
Bypass
Rate
Shape
Rate
Shape
Rate
Shape
Rate
Shape
Frame
Sync
Frame
Sync
Frame
Sync
Frame
Sync
AES
Rcvr
AES
Rcvr
AES
Rcvr
AES
Rcvr
PGM 2
PGM 3
Ref/PGM 4

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide Introduction
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1.4 Warranty and Feedback
Please take a moment to fill out the warranty card included with the unit and drop
it in the mail. This will enable us to contact you if there are any software or docu-
mentation issues. Also, we are very interested in your feedback. This unit was de-
signed based on feedback gathered from many broadcast engineers and it will evolve
further thanks to ongoing suggestions and comments from users such as you.
We look forward to hearing from you!

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide Introduction
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Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide
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Chapter 2: Connections
This chapter covers all required connections for the LA-5448.
2.1 Unpacking and Inspection
Before unpacking the unit, inspect the outer carton for shipping damage. If the car-
ton shows damage, inspect the unit in those areas. Please save the carefully designed
shipping carton and packing materials. In the unlikely event that the unit needs to be
returned to the factory, alternate cartons or packing materials may not be adequate
and can cause damage not covered by warranty.
The following essential items are provided with the unit:
• Two power cords (style to match shipping location).
• Small bag with replacement fuses and a handy permanent marker.
• This manual.
• Warranty information: Please fill out and return the warranty card to Linear
Acoustic to ensure your software and documentation are kept up to date.
2.2 Installation
StreamStacker LA-5448 installation requires:
• One standard rack space units with ADEQUATE VENTILATION (the unit uses
convection cooling via vents on the left and right sides of the unit);
• standard 75 BNC cables for digital signal connections;
To connect to digital equipment with 110  XLR connectors, we strongly recommend
the use of impedance-matching transformers (baluns) which are available from Canare,
Neutrik and other manufacturers. We know it is tempting to use shortcuts, and they
will sometimes work just fine, however failure of such approaches are usually random
and always seem to happen during the most expensive programming. We encourage
the use of the inexpensive and widely available baluns, especially in a transmission en-
vironment.

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide Connections
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2.3 Rear Panel
The rear panel of the Linear Acoustic LA-5448 contains all signal and power I/O.
WARNING: Replace fuses only with the same type and rating
2.3.1 Connection Ports
All of the LA-5448’s connections are on the rear panel and are described in detail below.
See Chapter 5: Specifications for specific pinouts.
Figure 2-1 Rear Panel
•Remote: This RS232/485/422 port is used for software upgrades as well as serial
remote control of the unit.
•Status: This is the GPI/O connection for parallel control of the unit. There are
four GP Inputs and four GP Outputs whose function, polarity, and type (i.e. held
or momentary) are adjustable via the front panel user interface. FUTURE
•Main Inputs (PGM 1-PGM 3): Connect the AC-3 signals that are to be pro-
cessed to these connectors. During power on and in the unlikely event of failure,
these inputs will be hard relay bypassed to the corresponding output connectors
located below each of them.
•REF/PGM 4: Apply 48 kHz AES reference, either PCM or AC-3.
WARNING: A reference AC-3 signal MUST be connected to REF/PGM 4 at all times for proper
operation. Plain AES reference can also be used.
•Main Out Pgm 1-4: Main AC-3 (Dolby Digital) programs one through four.
During boot up or in the event of failure, the Main Input connector directly
above each output will be hard relay bypassed to it.
NOTE: Front panel LEDs indicate input signal condition: Off=No Signal present,
Orange=AES sync detected but no AC-3, Green=OK.

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide Connections
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2.4 Quick Setup Notes
The LA-5448 requires only minimal setup to be up and running.
• Apply power to BOTH IEC AC power inlet modules.
• Note that once booted (~ 5 seconds), the front panel will display “No Refer-
ence” if no connections have been made to the rear panel.
• Connect a locally referenced 48kHz AC-3 signal (data rate or other parameters
do not matter) or an AES reference to the REF/PGM4 input
• Verify that the front panel indicator shows either a Green (AC-3) or Amber
(AES) signal has been detected on Input 4.
• Connect one or more AC-3 signals to be processed to the remaining PGM 1-
PGM 3 connectors
• Frame synchronized, rate shaped (to 448kbps) versions of these programs will be
produced at the corresponding Main Out Pgm 1-PGM 3 connectors.

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide Connections
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Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide
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Chapter 3: Applications
The LA-5448 is intended to be used in an emission (transmission) environment. This
chapter shows several applications of the system as it is intended to be used. Of
course other applications are possible:
•Frame synchronizer for multiple AC-3 streams, no rate shaping
• Frame synchronizer plus rate shaping for multiple AC-3 streams
Figure 3-1 LA-5448 processing three individual AC-3 streams, rate shaping disabled
Figure 3-1 above shows three sources being frame synchronized to a local plant ref-
erence signal. Data rates at the output are unchanged, but errors can be mitigated by
enabling Silent Frame mode.
Multiplexer
AC-3 448 kbps
Local 48 kHz AES Re
f
(AC-3 or PCM)
Satellite
AC-3 192 kbps AC-3
384 kbps
448
kbps
192
kbps
384
kbps
X
Synchronized to Local
Reference

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide Applications
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Figure 3-2 LA-5448 processing three separate streams, rate shaping enabled.
Figure 3.2 shows multiple AC-3 sources being frame synchronized to a local plant
reference as well as being rate shaped to a constant 448 kbps output data rate. Also
shown is a “crash switch” between two AC-3 sources that will be cleaned up and kept
at a constant data rate by the LA-5448. This is useful for commercial insertion appli-
cations.
Multiplexer
AC-3
448 kbps
Local 48 kHz AES Re
f
(AC-3 or PCM)
Satellite
AC-3 192 kbps AC-3
384 kbps
448
kbps
448
kbps
448
kbps
X
Synchronized to Local
Reference, fixed at 448 kbps
VTR/Server
AC-3
384 kbps
AC-3 384/448 kbps

Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide Applications
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3.1 AC-3 (Dolby Digital) Notes
The maximum data rate that is supported by the LA-5448 is 448 kbps. Rates higher
than this will be displayed as an error condition. When stream shaping is turned on,
no changes are made to AC-3 content. All metadata and audio parameters are passed
exactly as originally encoded with the exception that the data rate will now be fixed
at 448 kbps.
Several additional parameters and configurations are described below.
3.1.1 Output Mode
Typical external AC-3 encoders (i.e. Dolby DP569) or other AC-3 sources may have
several selections for output mode, which simply determines where inside an AES
pair the relatively tiny AC-3 data packets are carried. It does not matter which selec-
tion is chosen as long as the LA-5448 and the encoder match. The default for the LA-
5448 is Pro-32, the default for most known professional equipment that generates or
passes AC-3. The result of mis-setting this is that the output audio will mute.
3.1.2 Multiplexer Timing Issues
Tandberg encoders supply an AES reference signal that may be in the form of a fifth
wire with a BNC connector attached (later models), or it may be an XLR connector,
possibly of the opposite sex (i.e. an XLR Female) requiring an AES balun. There also
may be a menu setting to enable this reference output (automatically enabled in later
models). This reference MUST be used to drive the local AC-3 encoder’s reference
input. It is NOT necessarily the same as plant reference as it is derived from the en-
coder’s internal 27MHz clock. Save some headaches and lost sleep, and use this pro-
vided connection!
NOTE: Tandberg encoders provide an external reference output which MUST be
used to lock the local AC-3 encoder.

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Linear Acoustic LA-5448 AC-3 Frame Synchronizer/Rate Shaper User Guide
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Chapter 4: Menus
This chapter discusses how to use the front panel LED interface to access the menus. Most
of it is rather obvious, and a bit of experimentation will quickly make you comfortable nav-
igating through the submenus. The menus and submenus are structured to access more
complex functionality as you go deeper into the hierarchy.
The following two pages show the menu structure for the LA5124. All up/down access is
by the up/down front panel buttons, all left/right access is by the left/right (Prev/Next)
front panel buttons, and parameter changes (where applicable) are by the use of the rotary
encoder knob. When a parameter is changed, an asterisk (*) will be displayed next to the
parameter denoting that it has changed and that in order for this change to be stored, the
right (Next) front panel button must be pressed. To continue without storing the change,
press the left (Prev) front panel button.
Like all of our products, when in doubt you can simply use the Left Arrow (Prev) to back
out towards the Main menu level.