Broadcasters, distributors work toward solving sound glitches on diginets

Broadcasters and distributors are scheduled to meet on March 20 to try to come up with a plan to better manage audio levels on the new digital specialty television channels. The Canadian Cable Television Association (CCTA) is organizing the session in response to complaints from digital subscribers about varying sound levels across digital channel lineups. "We got complaints from cable customers about audio levels that were all over the map," says Michèle Beck, VP of regulatory engineering at the CCTA, which plans to provide broadcast technicians with recommendations for quality control of audio signals. The CCTA arranged for Dolby to send a digital monitoring box to Canada to test the sound levels of the various channels. The box was first used by CHUM Ltd., before being passed along to other broadcasters. With the Dolby monitoring equipment, it’s possible to get an average audio level during a period of dialogue in a channel’s programming to determine the proper dialogue normalization level (DAL). "We’re the first one to actually take (audio) measurements on our 12 channels," Bruce Cowan, CHUM’s director of broadcast technology, told CCR at the Canadian Satellite Users Association conference in Toronto on Feb. 19. "What is interesting is that we found the audio levels to be fairly consistent across our channels,…which tells me the problem is not specifically with the programming, but more to do with the distribution chain. "We’re just trying to get some consistency so that when people change channels, the audio level doesn’t put them out of their seat."He says the interim solution is to adjust the DAL at the digital video encoder either at the satellite uplink or at the cable headend. The most appropriate DAL value for each diginet would be based on the results of tests using the Dolby analyzer. At the March 20 session, the broadcast technicians will present their findings on DAL measurements for their respective channels, and the group will attempt to establish a direction on how best to adjust the audio levels. "We’ve found that these encoders are not set to the appropriate level for each service, depending upon the type of programming you have…I know for our services, all the DAL norm values are set the same, which is really not correct," Cowan states. "Because the DAL norm value for a music service should be different than a channel that is essentially talk, or a service like Bravo, which has different dynamics from MuchLoud." While making some adjustments in the headend encoders is a step toward improving the audio problems, Cowan points out that eventually producers will have to become involved. "Ultimately, what we need to achieve is setting the dialogue normalization level at the appropriate point during the time of production, so that when you’re producing digitally, that level would be set appropriately by the audio people, and that value would then travel with the digital signal from the broadcaster through the BDU and to the home set-top box. That would mean that the audio could change on a program-by-program basis versus a channel-by-channel basis." He says the process isn’t yet at the stage where the producer is involved, as broadcasters and distributors work toward obtaining some consistency in sound levels by adjusting the encoders for channels running programming that has already been produced. "It’s a problem that we need to work to try to improve. But I don’t consider it a major problem because it’s an annoyance that we know that we can do more to fix," Cowan concludes. Sound level problems have also manifest themselves with the analog specialty channels. This issue will also be examined at the March meeting.

Broadcasters, distributors work toward solving sound glitches on diginets

News | 03/01/2002 5:00 am EST

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