Maintaining Audio Quality in the Broadcast Facility 2011 - Orban

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in the Broadcast/Netcast Facility 51 Conventional AM, FM, or TV audio processors that employ pre-emphasis/deemphasis and/or clipping peak limiters do not work well with perceptual audio coders such as AAC/HE-AACv1/v2. The pre-emphasis/de-emphasis limiting in these processors unnecessarily limits high frequency headroom. Further, their clipping limiters create high frequency components—distortion—that the perceptual audio coders would otherwise not encode. In addition, several audio processing manufacturers offer pre-processing claimed to minimize codec artifacts at low bit rates. Orban’s technology is called PreCode. This manipulates several aspects of the audio to minimize artifacts caused by low bitrate codecs, ensuring consistent loudness and texture from one source to the next. PreCode includes special audio band detection algorithms that are energy and spectrum aware. This can improve codec performance on some codecs by reducing audio processing induced codec artifacts, even with program material that has been preprocessed by other processing than Optimod. Summary Maintaining a high level of broadcast/netcast audio quality is a very difficult task, requiring constant dedication and a continuing cooperation between the programming, engineering, and computer IT departments. With the constantly increasing quality of home and mobile receivers and stereo gear, the broadcast audience more and more easily perceives the results of such dedication and cooperation. One suspects that in the future, FM, DAR, and netcasts will have to deliver ever-increasing quality to compete successfully with the many other program sources vying for audience attention, including CD’s, DVD’s, Blu-ray disks, digital audio, subscription television, direct satellite broadcast, DTV, streaming programming on the Internet, high resolution downloads and who knows how many others! The human ear is astonishingly sensitive; perceptive people are often amazed when they detect rather subtle improvements to the broadcast audio chain while listening to an inexpensive car radio. Conversely, the FM broadcast/reception system can exaggerate flaws in audio quality. Audio processors (even OPTIMOD) are especially prone to exaggerating such flaws. In this discussion, we have tried to touch upon the basic issues and techniques underlying audio quality in radio operations, and to provide useful information for evaluating the cost-effectiveness of equipment or techniques that are proposed to improve audio quality. In particular, we concluded that today’s high-quality IC opamps are ideally suited for use as amplification elements in broadcast, and that compromises in digital standards, computer sound cards, disk playback, and tape quality are all likely to be audible on the air. The all-digital signal path is probably the single most important quality improvement that a station can make, but the installing engineer must be aware of issues such as lossy compression (particularly when cascaded), word length, sample rate, headroom, jitter, and dither, and 0dBFS+-induced clipping.
52 Maintaining Audio Quality Following the suggestions presented here will result in better broadcast/netcast audio quality—and that is a most important weapon in attracting and maintaining an audience that is routinely exposed to compact discs and other high-quality audio reproduction media. Provide your audience with the best possible experience. The future belongs to the quality-conscious.
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Robert Orban Greg Ogonowski Maintai
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Orban®, Optimod®, and Opticodec®
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Maintaining Audio Quality in the Broadcast Facility 2011 - Orban

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