Jeffrey Riedmiller

Delivering Scalable Audio Experiences using AC-4

AC-4 is a state-of-the-art audio codec standardized in ETSI (TS 103 190 and TS 103 190-2) and included in the DVB toolbox (TS 101 154 V2.2.1 and DVB BlueBook A157) and, at the time of writing, is a candidate standard for ATSC 3.0 as per A/342 part 2. AC-4 is an audio codec designed to address the current and future needs of video and audio entertainment services, including broadcast and Internet streaming. As such, it incorporates a number of features beyond the traditional audio coding algorithms, such as capabilities to support immersive and personalized audio, support for advanced loudness management, video-frame synchronous coding, dialog enhancement, etc. This paper will outline the thinking behind the design of the AC-4 codec, explain the different coding tools used, the systemic features included, and give an overview of performance and applications. It further outlines metadata aspects (immersive and personalized, essential for broadcast), metadata carriage, aspects of interchange of immersive programing, as well as immersive playback and rendering.

Audio for Digital Television

Audio is an area in television broadcasting and production that causes apprehension with some engineers because of its complexity and the care needed to get it right in design, installation, and operations. With the transition to digital television (DTV), there is a new level of uncertainty because the requirements for audio are far more advanced and complex than before. Yet digital audio provides significantly more sophistication, artistic creativity, greater processing power, and higher quality than its predecessor. This chapter provides a general overview of the key features and requirements of audio for DTV, a detailed review of one of the largest problems today (loudness), and some real-world suggestions on making it all work. By no means an exhaustive discussion of what is involved, the material here will at least bring to light what must be done, and a view of what is possible with television and digital audio beyond just getting a signal on-air.