EQUIPPING OBTRUCKS FOR HDTV

The Olympic Stadium viewedfrom the International

JASON POWER, MarketDevelopment Manager, DolbyLaboratories, explains some ofthe implications of HD for

OBs.

High Definition TV services havebeen available for several years inthe US and Japan, but the launch of

HD services in Europe has only recentlybeen announced – with many Europeanbroadcasters planning to go on air withHDTV by early 2006. The falling prices of‘living room friendly’ flat-screen displaysand the availability of new codingtechnology that enables HD broadcasts tobe squeezed more easily into Europe’scrowded broadcast spectrum are oftenmentioned as factors that make HD moreviable in the region than ever before.

From the viewer’s point of view, theoverall HDTV experience is more vivid,more realistic, and plunges them into thecentre of the action. This experience iscreated not just by larger images withgreater resolution, but is completed byimmersive 5.1 surround sound. It isexpected that sport will feature significantlyin early HD programming in Europe – oneof the three new satellite channels plannedto launch later this year by Germanoperator Premiere will be devoted to sport.So how is Europe’s outside broadcast

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industry preparing for this rapidly

developing demand for live HDprogramming with 5.1 sound?

Several major outside broadcast facilityproviders have already equipped trucksready for HD production, but providingsurround sound involves more than justinstalling a 5.1 capable mixing console andsuitable monitoring. The truck needs to beable to deliver the mix in the format thatthe broadcaster wants to use to feed it backto the broadcast centre via their telecomslink, or to record onto tape. The mostcommon format used for this purpose isDolby E, which enables up to eightchannels of audio to be fed over a standarddigital stereo AES link.

Additionally, where the final mix isbeing generated in the truck, the mixershould ideally also be generating themetadata that will ultimately be broadcastalongside the audio. This metadata is usedto control how the mix will sound whenreplayed on different home systems, andcan be used to optimise stereo and monocompatibility.

OB Trucks at the Olympic GamesNever were OB trucks tested as much as atlast year’s Olympic Games in Athens.Twelve trucks covered more than 14venues and 16 different sports in surroundsound at the Games – and many engineershad never mixed in surround before. Thesurround sound feeds they produced wereoffered to broadcasters around the world to

Broadcast Centre

transmit their Olympic coverage in Dolby

Digital 5.1, or in Dolby Pro Logic II forthose limited to stereo sound transmissionchannels.

Just two weeks before the Gamesbegan, Dolby consultants flew to Athens tosupport the final installation of equipmentby the host broadcaster Athens OlympicBroadcasting (AOB), prepare their mixingteams, and provide assistance throughoutthe Games coverage. In total, 51 Dolbyunits were employed by AOB throughoutthe broadcast chain, including encoders,decoders, test tools, and loudness meters.

Dolby sound consultant, AndreaBorgato visited each of the 12 outsidebroadcast trucks in turn to install andcalibrate the equipment, and helped to trainthe sound mixers in surround productiontechniques. Broadcasting live sport is acomplicated process and so surround audioproduction is generally kept relativelysimple. However, the mixers at theOlympic Games still managed to provideseveral mixes simultaneously using a singlemixing console (International TV mixes in5.1, Pro Logic II encoded stereo, and plainstereo – plus the International Radio Stereo Mix).

Preparing the OB trucks for mixing andmonitoring was made that bit morecomplicated as many of them weredesigned only for stereo production. Soeach truck was equipped with a rackcontaining a DP571 Dolby E Encoder for 5.1sound feeds, as well as a DP563 Encoderand a DP564 Decoder for the Dolby ProLogic II feeds. Vistek units to compensatefor video re-synchronisation delays wereincluded in the rack, and Voice Systems’BEEE 5.1 loudspeaker monitoring wasprovided, with SPL model 2380 surroundmonitoring controllers.

Capturing the SoundIn the production of 5.1 extra microphonesare typically used to capture the rearchannel ambiance and to help give theviewer that sense of being in the midst ofthe action. Generally, standard stereo micconfigurations were used for the frontalimage, supplemented in most of the venueswith a spaced pair to provide the rearchannel contribution of the environmentand crowd.

By far the most complicatedmicrophone setup at the Olympic Gameswas in the main Olympic stadium whichplayed host to the athletics, the footballgold medal match, and the opening andclosing ceremonies. A number of miniatureshotgun microphones covered the actionon the track, supplemented with additionalstereo microphones. The crowd was picked

up with five microphones hung around the

broadcasts.

Dolby Processors in OB truck rack

www.dolby.com

stadium, as well as by extra crowdmicrophones for smaller localised events.

A strategy was developed to enable asingle audio mixer to create all of thevarious stereo and surround mixes needed.For example, in the 5.1 mix, the centrechannel was kept free to simplify theaddition of commentary by localbroadcasters and to simplify mixing onstereo consoles. This also meant that thefront left and right channels of the 5.1 mixcould be used as the international stereo FXmix. The disadvantage of this approach wasthat the centre speaker could not be used toanchor the sounds of on-screen action for5.1 listeners, but this was considered to bean acceptable compromise.

A basic set of metadata was createdwithin the Dolby E encoder at each locationfor the rights-holding broadcasters to use asa guide, but it did not prove necessary tomonitor or adjust metadata in the truckwhilst mixing. Since the 5.1 was aninternational mix, each individualbroadcaster was left to create or modify themetadata once they had added their localelements (such as commentary in thecentre channel). Each event’s 5.1 mix andaccompanying metadata was encoded as

Dolby E, embedded into an SDI signal andtransmitted to the Olympic broadcastcentre via a standard fibre-optic link.

Production ChallengesThe complexity of the coverage and thesheer number of events to cover presentedsome unique difficulties, which oftenresulted in some equally unique solutions.For example, the sound mixer for the trackevents shared a console with the mixer forthe field events – yet even in this difficultenvironment, he was still able to create andmonitor a surround sound mix. When hiscolleague was using the surroundmonitoring in the truck, he used DolbyHeadphone technology to listen to a guideversion of the 5.1 mix. Of course, the oddnudge was needed to alert him to importantcalls over talkback!

Examples such as this demonstrate that,even in circumstances where productionfacilities are not optimised for 5.1, aconvincing surround soundtrack can becreated without compromising theproduction of the other required feeds.Fortunately, in Europe where use of 5.1 isspreading even on standard definition (SD)television, many broadcasters are already

devoting more care and attention to 5.1production without adding prohibitivecomplexity. With demand for 5.1 audiogrowing, there is every chance that livesurround sound production will continue tobe an area of innovation, and withinternational events such as the WinterOlympics and the football World Cup takingplace in Europe next year, it should be anexciting time for audio in outside

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