Broadcast Engineering - February 2009 - (Page 20)

TransiTion To digiTal Digital hanDbook Provide new viewer services by implementing the DVb/EtSi coding specification. By DaviD austerBerry Digital audio a receiver for one national market. One example is audio description. If it is not included as a standard feature, then receivers that do support audio description are manufactured in small volumes, resulting in a high price tag. This puts them outside the reach of many potential users. Because of the flexibility of the DVB standard for video and audio services, this had led to several different receiver specifications. Receiver manufacturers prefer as large a market as possible to gain the efficiencies W hen the DVB Project developed the digital television standards that have been adopted across Europe, the means of encoding stereo and surround audio was mandated in detail. Early services were SD, and were a multichannel replacement for existing analog transmissions. With the rollout of HD services across the region, the provision of enhanced features has become more important as viewers’ expectations increase. User control of audio description level most common), and support for disability services. DVB/ETSI coding specification The DVB standard for audio and video coding was released in a first edition in 1996. The current edition is now an ETSI standard, TS 101 154, last published in 2007. This version gives guidelines for encoding to a number of standards, including the MPEG family (1, 2 and 4), Dolby and DTS. However, it does not specify which codec should be used. It does lay out a mandatory implementation of the codec(s) chosen by an operator. The service in one country may only provide a subset of the possible audio features, and will have been specified by a government regulator for an over-the-air service or by the service provider — a satellite or cable operator — for subscription services. The ETSI standard refers to an integrated receiver and decoder (IRD), which could be a set-top box or a television set with an integrated digital tuner. Early SD services used MPEG-1 Layer 2 stereo coding. With the onset of HD transmissions, surround sound has become an additional requirement. The EBU developed a service requirement for free-to-air HDTV receivers (Tech 3307, 2005) to provide a common feature set. This stipulates a minimum of 5.1 surround, but does not recommend any codec from those listed in the ETSI standard. It also includes low bit rate audio services for the sensory impaired (audio description) and dynamic range processing. National governments have developed more wide-ranging specifications to cover satellite, cable and IPTV receivers. Examples include the NorDig specification from the Nordic Decoded mono audio description Decoded main program audio L R Σ Σ Control metadata to dip program sound during description User control of overall level Figure 1. Audio description allows a commentary to be optionally added to the main program audio. As HDTV services are being introduced alongside existing SD digital services, there have been moves to reduce the number of variables in the audio feature set. Some early digital broadcasters and pay-TV operators used different subsets of the features in the DVB standard, leading to the requirement for special features in of scale. This is driving efforts by the EBU to create a recommended practice that could be adopted across the region, leading to lower manufacturing costs for STBs and TV sets. In Europe, the common features required from an HDTV receiver are surround sound, operation with up to four languages (with two being 20 broadcastengineeringworld.com | February 2009 http://www.broadcastengineeringworld.com

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Broadcast Engineering - February 2009 Contents Viewing the Slowdown in 3-D Examine Workflows Tapeless Technology Digital Audio 24p and 25p Judder Video Routing: A Look at What's Next Managing AFD The Right Connections Solid State Logic's AWS 900+ SE and More... Advertisers Index

Broadcast Engineering - February 2009

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