DAB+/DAB Surround

The ETSI standard DAB+ is based on the original DAB (Digital Audio Broadcasting) standard. For higher audio quality it employs the audio codec High Efficiency AAC (HE-AAC) v2 which delivers excellent sound at very low bit rates. As a result, DAB+ provides significantly greater bandwidth efficiency than conventional DAB allowing up to three times the programs per channel compared to traditional DAB. DAB+ is designed to provide the same functionality as the original DAB radio services, including traffic announcements and PAD multimedia data.

DAB+ features:

• HE-AAC v2 delivers exceptional performance efficiency
• More stations can be broadcast on one multiplex (greater station choice for consumers, more efficient use of radio spectrum, lower transmission costs for digital stations)
• Compatible with existing scrolling text and multimedia services
• Robust audio delivery
• Optimized for live broadcast radio
• Fast re-tuning response time (low zapping delay)

The audio codec DAB Surround is designed to bring multichannel sound at stereo bit rates to DAB/DAB+ services by combining HE-AAC v2 with MPEG Surround. Broadcasters can provide 5.1 surround at a total audio sub-channel bit-rate of only 96 kbit/s or less.

DAB Surround features:

• multichannel sound at stereo bit rates
• no need to simulcast stereo and multichannel programs: stereo and surround signal are broadcast in one single stream.
• compatible with existing stereo and mono receivers
• Surround quality is similar to that offered by discrete systems at substantially lower bit rates, and superior to that achieved with matrix-based systems

DAB Surround supports a binaural mode to play back surround sound over conventional stereo earphones.

DAB+ is the successor of DAB and can be applied for new digital radio services as well as it can enhance already existing services based on DAB. Especially services suffering from poor reception conditions benefit from DAB+ and its highly efficient audio codec.

For broadcasters and receiver manufacturers, Fraunhofer IIS offers DAB+ encoders and decoders as well as professional broadcast server systems. HE-AAC v2 encoders and decoders optimized for the DAB+ transport layer are available, including super-framing capability and comprehensive PAD support. Fraunhofer IIS provides these codecs for various PC platforms, a wide range of fixed-point and floating-point DSPs, and embedded processors. All have been successfully tested for compatibility with other DAB+ implementations. These codecs can also be obtained in combination with the highly optimized multichannel extension MPEG Surround.

See also

• MPEG-4 HE-AAC v2
• MPEG Surround

The Fraunhofer DAB/DMB Content-Server™ is available as the professional broadcast solution with full DAB+ and DAB Surround support. The ContentServer for Eureka 147 Digital Audio and Multimedia Broadcasting is an easy-to-use encoder system for the DAB/DMB broadcast chain. It features real-time audio and video encoding in MPEG Audio Layer 2, MPEG-4 HE-AAC v2 (DAB+), MPEG Surround, and MPEG-4 AVC, as well as the generation and insertion of all kind of data services in PAD and NPAD, like Journaline, Dynamic Labels, Slideshow, TPEG and EPG.  

See also

• Fraunhofer DAB/DMB ContentServer
• MPEG-4 HE-AAC v2
• MPEG Surround

DAB Surround is based on the MPEG Surround standard and enables any digital radio service to broadcast in surround. A generic surround extension, MPEG Surround can be used in conjunction with HE-AAC v2 (DAB+).

The DAB Surround technology works as follows. A compact set of parameters representing the spatial image of the original surround signal is transmitted along with an automatic mono or stereo downmix. Alternatively, an externally created downmix signal (‘artistic downmix’) may be used. On the decoding side, the transmitted downmix signal is expanded into high-quality, multi-channel output based on the spatial parameters. MPEG Surround offers an impressive sound quality similar to that provided by discrete systems and substantially beyond that of traditional matrix-based surround systems commonly found in the marketplace today.

The resulting audio quality is very close to that provided by a fully discrete surround system, despite the fact that the surround image is represented by a very low additional bit rate, typically in the range of 4-10 kbit/s. The data rate for the surround parameters is scalable from 3 kbit/s up to 32 kbit/s (and beyond), allowing a variety of application scenarios to be addressed.