Tempe, AZ (January 24, 2007)–A Model LA-5448 Multi-Input AC-3 Synchronizer and Rate Shaper supplied last July by Linear Acoustic to KAET-TV, the PBS member station based at Arizona State University, is being used to seamlessly switch between incoming PBS multichannel audio soundtracks in AC-3 format and locally originated programming.
“We prefer to switch AC-3 bitstreams directly,” said KAET-TV chief engineer Terry Harvey, “simply because it avoids a series of decode and re-encode audio processing stages that can degrade audio performance. And we can switch and splice compressed AC-3 audio streams without additional complicated routing systems. We place a high priority on providing outstanding sound quality for our local PBS community, and the LA-5448 was the only way to go.”
Use of the LA-5448 Synchronizer and Rate Shaper also ensures that the essential metadata parameters encoded at PBS’ Washington headquarters, including DialNorm, are preserved and on-passed to consumer receivers and set-top boxes.
The LA-5448 Synchronizer and Rate Shaper was designed specifically by Linear Acoustic to correct timing and synchronization anomalies in AC-3 digital audio bitstreams, and eliminates many problems caused by poorly formatted signals. “The LA-5448 maintains consistent, error-free AC-3 bitstreams that are critical for high quality audio transmissions,” offered company founder Tim Carroll, an acknowledged expert in multichannel audio.
“To prevent multiplexer issues, audio bitstreams delivered from sources outside of the local plant must be synchronized to local reference, free of errors and of a consistent data rate. Decoding and re-encoding AC-3 is expensive and can affect audio quality due to metadata being lost, and is therefore no longer an option. Model LA-5448 satisfies these requirements and more, all without re-encoding.”
The unit performs frame synchronization, error correction/concealment and rate shaping for up to four separate AC-3 streams in 1U rack unit.