The 8685 is Orban's second-generation surround/2.0 processor. In addition to the effective automatic loudness control of its predecessor, the 8685 offers new input/output capabilities that include support for SDI and HD-SDI and for Dolby E. Dual redundant power supplies help ensure maximum uptime. In addition to surround processing, the 8685 can simultaneously provide up to three channels of 2.0 processing, allowing it to provide all the audio processing necessary for a typical ATSC broadcast with multiple subchannels. Like the 8585, the 8685 is dialnorm-aware. Loudness control is excellent when measured by the ITU BS.1770-2 and EBU R-128 standards or by the 8685's built-in CBS Loudness Meters, allowing stations to comply effortlessly with the requirements of the CALM act.
Experience has shown that the mass television audience wants two things from television audio: dialog should be comfortably intelligible and commercials should not be irritatingly loud compared to program material. Home theater owners may want the opportunity to watch feature films while hearing a wide dynamic range signal. However, even these viewers usually consume television in a much more passive way when viewing garden-variety programs. To be an acceptable part of the domestic environment, television sound cannot overwhelm household members not interested in viewing (not to mention neighbors, particularly in multi-family dwellings). For a variety of reasons, the dynamic range of sound essential to the intelligibility of the program should not exceed 15 dB in a domestic listening environment. Underscoring and ambient sound effects will, of course, be lower than this.
The issue of loud commercials is particularly important. In the U.S., it is against Federal Communications Commission rules to broadcast irritatingly loud commercials. As a result of viewer complaints, the FCC has twice investigated the problem.
Orban understands such issues well. Since 1980, they have provided analog television broadcasters with industry-standard dynamics processors: Optimod-TV 8180, 8182, 8282, and 8382. In 1998, they introduced Optimod-DAB 6200 - two-channel processing specifically tailored for digital channels using lossy compression like Dolbys AC-3, which is used for ATSC transmissions. The 6300, introduced in 2006, is a second-generation two-channel processor for digital channels, including DTV, DAB, and netcasting.
In typical analog television practice, all audio is applied to a single transmission audio processor that automatically controls the average modulation and the peak-to-average ratio while smoothing out transitions between program elements. Simple compression and peak limiting cannot do this effectively. Starting with the 8182, all Optimod-TV processors have incorporated the CBS Loudness ControllerTM.
Developed after 15 years of psychoacoustic research at CBS Laboratories, the CBS LC accurately estimates the amount of perceived loudness in a given piece of program material. If the loudness exceeds a preset threshold, the controller automatically reduces it to that threshold. The CBS algorithm has proven its effectiveness by processing millions of hours of on-air programming and greatly reducing viewer complaints.
In ITU parlance, the CBS LC relies on a "short-term" loudness measurement that takes into account the human ear's loudness integration time - approximately 200 milliseconds. The CBS algorithms attack time is fast enough to prevent audible and irritating loudness overshoots - blasts of sound that have viewers scrambling for their remote controls. Loudness control is always smooth and unobtrusive. Unlike "long-term" loudness measurement and control technologies, the CBS LC recognizes that a piece of program material whose average loudness seems acceptable according to a long-term loudness measurement may nevertheless have short sections whose loudness should be reduced because it is extremely annoying. While main purpose of this processing is to control the loudness of commercials, other exuberantly mixed elements can also benefit.