Lancaster, PA (December 19, 2005)–Linear Acoustic has been invited to address the Society of Broadcast Engineers on ways to control and maintain consistent audio levels during multichannel HDTV transmission. Company president Tim Carroll, a surround sound technologies expert, will speak to the Sacramento SBE Chapter 43 on January 24, 2006, and San Francisco SBE Chapter 40 on January 25; both are noontime lunch meetings.
“Through the use of AC-3 audio data compression technology–better known as Dolby Digital–DTV has the capability of delivering pristine quality digital audio,” Carroll stated, “with a potential dynamic range exceeding 100 dB on each of its 5.1 channels, equaling or surpassing the performance of a high-quality movie theater. While such a specification looks good on paper, and is referred to as ‘What Hollywood has always asked for,’ it is unclear whether this dynamic range is appropriate for the typical television viewer.”
“Importantly,” Carroll emphasized, “the AC-3 system makes a basic assumption that audio dynamic range and program loudness are separable and can be controlled independently. This is a dramatic departure from the actions of legacy broadcast dynamic range processors installed at so many broadcast stations and networks. While there are some controls built into the so-called metadata portion of AC-3 to help tailor the audio for appropriate presentation to each listener, these parameters must be set correctly on each program for the system to function effectively. Which means that current audio producers must not only take care to make good quality audio, but also take the time to author proper audio metadata. Assuming this takes place, are there any guarantees that the metadata will make it intact all the way to the point of transmission? What if it fails or is maliciously set incorrectly?”
Carroll considers that the question of controlling dynamic range boils down to a single question: Is it all working? “In an effort to answer this question,” Carrols said, “my presentations to the SBE Chapter Meetings will explore some real-world scenarios and their measured results. I will present actual examples of successes and failures, and the root cause of each will be described along with technical details of several add-on solutions designed to help broadcasters and consumers. And I will also take a few minutes to explore surround for digital radio and discuss some of the technical challenges emerging in this new market.”