Linear Acoustic LA-5448, User Manual

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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.