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[Tuesday at NAB]
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Audio Splits for the Good of the Band
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by Kelly M. Brooks ,
~ April 15, 2008
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RADIO WORLD
As broadcasters large and small continue to bicker over HD Radio and its pros and cons, Wheatstone/Vorsis Technical Director Jeff Keith reminds them what should be a main objective of radio stations in any market: “Ensuring the very best signal is delivered to the listener regardless of how they might choose to listen.”
Keith adds that in order for a station to improve or even maintain its ratings, “Processing capable of shaping the station’s sound so that it sounds good on any receiver, analog or digital, is key. … Algorithms have been under development that are faster and smarter, making them capable of providing a smoother and more competitive on-air sound without the usual audible side effects.”
In short, both listener and station win with good audio processing, and the offerings at this year’s NAB Show make it easy to attain.
Equipment manufacturers, cognizant that today’s multifaceted radio stations are both demanding and requiring more from their processors, are touting multiband, increased DSP horsepower, better loudness control, absolute peak limiters and look-ahead algorithms that anticipate and eliminate over-modulation peaks before they occur as the must-have features for broadcast audio processors.
GET SMART
A proliferating number of bands is the new standard, addressing the limitations of past processing by splitting the audio into more frequency bands and processing each one separately. The result is super-clean and clear audio.
Processing flexibility also is important in today’s broadcast environment of HD Radio multicasts and Internet streaming.
“From conventional terrestrial transmission, to a plethora of coded audio systems, processing must be flexible enough to manage all of these methods,” said Omnia President Frank Foti.
“Additionally, processing must be smart enough to understand the embodiment of content. With mastering practices becoming more like traditional radio processing, on-air signal conditioning must be able to recognize the sonic signatures of content, and adapt itself accordingly, or added distortion results. Methods of this nature are a far cry from the simplistic static dynamic functions of yesterday.”
And as units get smaller, DSP power keeps getting bigger. “DSP power, host processing power and memory density have increased 100 fold in the past five years while the size, cost and power consumption of these devices has been decreasing nearly as rapidly,” said Tim Anderson, FM/digital radio product line manager for Harris Broadcast. “Dedicated, embedded processors allow for the design of ever-more-complex algorithms, look-ahead processing, psychoacoustic analysis and even format encoding in a single box.”
What was once an added or special feature is likely standard on this latest batch of audio processors, with many enhancements borrowed from our friends in television, as the push to digital continues to push right on through the wall that separates us.
“Nearly everything is being designed with what were once advanced features such as Web-enabled GUI interfaces and Ethernet access, SNMP notification and integrated diversity delay,” said Anderson.
“Many of the radio technology advancements today are being leveraged from television as the lines between the two mediums become blurred in the digital realm. These systems are now being designed to be faster, smarter, more cost effective and more reliable than ever before.”
New offerings from Wheatstone and its Vorsis line include the AP-1000 31-band digital spectral processor, now equipped with the Vorsis Bass Management System algorithm in the FM limiter/clipper section, and five-band AGC. The factory presets also have been refined, and there are now more than 50 tuned custom presets included.
Additionally, the FM-5 audio processor has been added to the Vorsis series. Features include a proprietary five-band multiband dynamics controller, and precision 10-band final limiter with distortion-masked clipper. The FM-5 also ships with additional custom presets.
“The FM5 and AP1000 FM audio processors have been helping engineers, program directors and audio consultants achieve on-air loudness and quality,” said Keith. “Both processors provide on-the-dial loudness while still sounding natural, musical and pleasing to the station’s listeners.”
Omnia is debuting its Omnia.8X, which processes eight channels at once. Features include eight stereo processors in the 2 RU chassis, each with three bands of AGC, wideband AGC, look-ahead final limiter and Omnia Bass Management, numerous presets, as well as networked remote control and configuration using a standard Web browser.
Also making a Vegas debut is the Omnia One FM audio processor. Features include a distortion-controlled pre-emphasized final limiter/clipper; four-band AGC to add consistency and build density before the limiter stages; four-band peak limiter using feedback limiters for the lower two bands (optimized for bass punch and lower mid-range warmth); and feed-forward limiters for the upper two bands.
Omnia processors also feature the company’s Sensus technology, “where the audio processor is able to modify its internal algorithmic architecture. This enables advanced algorithms designed to improve broadcast quality, [and is] applicable to both conventional and coded transmission systems,” said Foti.
He said the Omnia.8X also is suitable for surround-sound broadcast, fast gaining in popularity, particularly in the car.
“Consumer market research indicates surround sound is one of the most sought features in automobile listening,” he said. “Now, through the use of an innovative transmission system, we are able to add discrete surround sound, not tricked up matrix, to conventional FM broadcasting.
“This provides the ‘wow’ factor consumers desire, and creates a mechanism enabling broadcasters to compete for listeners who are able to hear surround in other media formats.”
Orban/CRL is introducing the Optimod 8585 digital surround audio processor. The manufacturer builds on its Optimod 6300 two-channel processor and incorporates multichannel processing that reflects the latest psychoacoustic research into loudness perception.
The 8585 features two- and five-band audio processing for surround sound broadcasting, netcasting and mastering. The company highlights features such as compression ratio controls and a look-ahead peak limiter, which it said makes the unit suitable for mastering audio in broadcast productions, as well as productions intended for media such as DVD and BluRay.
A third-generation CBS Loudness Controller helps retain audiences by controlling subjective loudness and annoyance, according to Orban/CRL. The controller works in both two-band and five-band modes.
SAMPLING THE SPECTRUM
Audemat is introducing the 3U Digiplexer 246, or “Radio All in One.” It includes a digital audio processor (two-/ four-/six-band), RDS and stereo generators, transmitter remote control capabilities, backup audio-over-IP capabilities and an Ecreso FM exciter (1, 20 or 100 W).
Audio processing specs for the four-band version include 192 kHz sampling frequency for processing, and 1.5 MHz sampling frequency for final clipper. Audemat describes the digital stereo generator as accurate and stable, adding that audio bandwidth can be expanded to 17 kHz without affecting the pilot.
“The Digiplexer 246 has an Ethernet port that can be used as an additional audio input. It can stream the audio from a remote server for audio back up application or as a main audio source,” said Christophe Poulain, executive vice president, Audemat Inc. “Reliability is crucial for such a product. That’s why we have decided to port the Linux-based OS on a CF card instead of a HDD.”
Inovonics has a Rev. 2 firmware upgrade for its Model 261 digital utility processor. Introduced at the 2007 convention, the company describes the 261 as a simple “workhorse” stereo-AGC, compressor and limiter to provide audio level consistency in production applications, and to give protection limiting for STLs and satellite links.
Rev. 2 firmware adds optional independent pre-emphasis protection limiting to the Model 261, making it suitable for LPFM and similar air chain uses that do not require multi-band processing.
Aphex Systems is featuring the Model 240 dual logic-gated Easyrider Compres-sor, billed as a low-cost solution for processing incoming phone lines. Each of the two channels combines the Logic-Assisted Gate with the Easyrider Compressor.
The Model 240 links the gate and the compressor so that the processing of both the gate and the compressor are “even more seamless,” said President Marvin Caesar.
“Phone signals vary greatly in level as well as in noise floor. On-air processing corrects the levels, but often brings up the noise from the phone line to an unacceptable level. The Model 240 smoothes the level of the incoming phone line, and reduces background noise while maintaining clarity and intelligibility. The Model 240 frees the jock to think about what the caller is saying rather than riding levels or pushing mute buttons.”
Sonifex is showing its Redbox RB-SSML1, a 1U rack-mountable source selector for compressing or limiting an incoming microphone or line signal, along with selectable level metering and headphone monitor outputs. The unit is mainly used in situations where level control is required, such as voiceover applications.
The compression ratio and threshold limits are adjustable via linear pots located on the front panel. The threshold can be set between –30 dBu and +20 dBu. When the input signal rises above the threshold level a soft-knee compression is applied at the selected ratio. The compressor has an attack time of approximately 20 ms and a release time of approximately 400 ms. The Redbox RB-SSML1 also can work in bypass, where no compression is applied.
Harris is introducing several upgrades to its FlexStar line of HD Radio equipment, including a Host Audio Extraction feature that takes place within the E2X (exporter-to-exciter) link.
It takes the encoded MPS audio from the exporter and decodes it back to audio at the exciter for use as the legacy analog program audio, thus eliminating the need for a separate STL audio stream dedicated to the analog FM signal. Program content for both the HD Radio and analog signals is provided over the E2X link.
The audio for the host FM signal is extracted from the E2X stream by the FlexStar HDX exciter through the HAX daughter board and presented as AES-3 audio on the rear XLR connector of the exciter. This allows the FM audio to be processed externally using traditional FM audio processors.
As the system delay is now identical for both the analog and HD-R audio streams, the only additional diversity delay required is 4–5 seconds to compensate for the receiver’s additional digital processing latency. This delay is adjustable and incorporated into the HAX adapter.
“Using only the HD Radio encoded bit stream for transport over the STL, the host analog audio is extracted at the transmitter site through the exciter where it can then be processed separately as traditional main program FM audio,” said Anderson. “With proper preconditioning of the HD-R codec, bit rates of 32 to 96 kbps can provide high-fidelity transport of the main program analog FM and HD-R audio over smaller, less expensive data circuits than have been required to date.”
Logitek said it continues to enhance the audio processing functions available in its routing and console systems. User-configurable profanity delays, EQ and dynamics functions have been updated in the company’s Supervisor software with enhanced detail and graphical displays.
Jünger Audio is showing its C8086 M, an eight-channel Level Magic surround processor; C8601 Dolby E decoder for the C8000 system; and C8611 Dolby E encoder.
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