Loudness control is an important issue in the broadcast industry today. In response to audio loudness concerns, President Barack Obama signed the CALM Act in December 2010 outlining information and guidelines for loudness control.
Upon implementing this technology, an important question is: At what stage should loudness control be integrated? There are three strategic locations in a broadcast facility that the loudness control processors are being placed: at the signal acquisition stage, master control stage or at transmission just prior to the encoding stage. All three locations are feasible; however, the loudness control location is ultimately determined by the specific internal practices of the individual facility. Therefore, the user can purchase a processor that accommodates his or her needs.
To achieve loudness control at any stage in the broadcast chain, Evertz offers its IntelliGain loudness processor, which can be added as an option to many of its products.
Loudness control at signal acquisition stage
Loudness control is often applied when the signal lands and is ready for baseband video processing. It can be applied at the output of the IRD, fiber receiver, frame synchronizer or at the output of a playout port from a media server. (See Figure 1.) IntelliGain allows loudness to be controlled at the acquisition stage, thereby enabling the user to adhere to the CALM Act.
Evertz's MPEG decoder products, such as the 3480DEC18-MP2SD and 3480DEC6-MP2HD bulk MPEG-2 decoders, offer high-density MPEG-2 decoding with integrated loudness processing technology on all 18 or six decoded outputs respectively. For further acquisition solutions, the company's 7812 and 7746 series of up/down/crossconverters and frame synchronizers provide an integrated system that enables a central point for monitoring audio and video signal integrity. To meet specific target loudness levels, loudness control at the acquisition stage normalizes all signals coming into the facility before any downstream plant processing. This establishes a target level for all audio flowing through the facility, thereby allowing any deviations in audio levels to be identified and controlled before entering the transmission stage.
Loudness control at master control stage
Another common location for loudness deviation to occur is during master control. This is because the master control stage experiences high levels of traffic due to transitions between multiple program feeds and commercial servers.
To deal with audio loudness at the master control stage, the EMC Evertz Master Control and Switcher platform has been designed with integrated IntelliGain technology. The smart loudness processor will enable the user to monitor and trend audio loudness in real time, thereby achieving target levels. The automation function enables the user to oversee a wide range of audio signals passing through the master control, which include voice-overs and discrete audio tracks, such as Dolby-E encoded audio. In relation to Dolby-E encoded sources, it is beneficial to apply loudness control at the master control stage as the EMC allows audio handling to decode, mix and re-encode the audio data, while the loudness processor manages the Dolby metadata to correspond with the defined target loudness.
The automation capabilities of this loudness control technology allow the user to configure the loudness control engine so that gain control is only applied during commercials and interstitials and therefore does not affect the program segments.
Loudness control at transmission stage
The most common location for audio loudness control is at the transmission stage. (See Figure 2.) Any undesirable audio levels are identified here before entering the compression ring. Loudness control at this stage is beneficial because undesirable audio levels are dynamically adjusted to meet the target level before it reaches the end of the chain. IntelliGain technology makes loudness control simple at this stage because of its flexibility and availability on a wide range of automatic protection changeovers; integrated Dolby-E and Dolby Digital audio encoders; and professional MPEG-2 and H.264/AVC HD and SD-SDI encoders. The loudness control processor enables backup protection and performs real-time automatic loudness control on the program output.
If a facility wants to maintain specific target loudness or perform real-time monitoring to keep records for future recall, it is good practice to apply loudness control at the transmission stage. At this stage, the user can also employ the loudness control processor to confirm that the dialnorm level is programmed correctly. The loudness control processor is capable of transmitting audio trending information samples over SNMP to VistaLINK, which enables loudness calculations to be logged and analyzed for compliancy.
Managing audio loudness for an entire system
The IntelliGain option for VistaLINK NMS provides the capabilities necessary to manage the audio loudness for an entire system. Because the FCC is responsible for ensuring that facilities are complying with the loudness guidelines and therefore must police the average loudness levels over time, it is crucial that the recorded audio levels are accurate. To prove compliancy with the CALM Act, it is essential that facilities log and track audio levels with the ability to datamine the necessary information. IntelliGain provides a central location to configure, store and analyze all signal metrics including loudness throughout the plant. Therefore, the system is completely accessible with the ability to extract the necessary logs.
The modular core technology of this processor allows control to be added as a soft ordering option on a module-by-module basis, providing advanced integration, flexibility and cost savings.
Tony Zare is product manager, modular products, at Evertz Microsystems.
