Press Release

AUDI AG, Ulrich Leierseder, Head of Multimedia Development

 

The first radio transmissions were made more than one hundred years ago, at that time still in mono. The transmission method was amplitude modulation (AM), with which people will be familiar from the medium and long-wave bands, for instance. When VHF with frequency modulation (FM) was introduced more than fifty years ago, it brought a substantial improvement in sound quality; this led to the appearance on the market of the first stereophonic revolution from the USA at the start of the 1960s. For many years the magic word "stereo" was synonymous with high-quality sound reproduction.

 

In the same way that the vinyl record was supplanted by the CD, digital media are currently gaining the upper hand in the field of radio transmission technology. The advantages are plain to see: like the audio CD, digital radio provides better sound quality, is easier to handle and offers a large number of additional features.

 

Digital Audio Broadcasting DAB

 

In Europe, digital radio is available in the guise of Digital Audio Broadcasting (DAB). The most outstanding feature of DAB is interference-free reception of a sound quality similar to a CD. The hiss that is often encountered with VHF receivers has thus become a thing of the past. DAB furthermore makes a greater variety of programmes and an extensive range of supplementary information possible. Between 5 and 9 programmes are grouped together in an ensemble that is broadcast either regionally or nationally.

 

The launch of DAB digital radio means that there is now a modern broadcasting method that overcomes the drawbacks of stereo FM radio, while offering a wide variety of options for extended features.

 

One of these possible extended features is the improvement of traffic information, which is an established feature on FM in the form of TMC (Traffic Message Channel). It is used to enable dynamic route guidance for navigation systems. DAB in conjunction with TPEG (Traffic Protocol Expert Group) represents a major step forward thanks to the more detailed information available.  TPEG means that the location of an accident, for instance, can be displayed with a precision of one metre and is not expressed merely in terms of crossroads and junctions, as with TMC. The TPEG concept has been kept sufficiently general that other applications, such as the incorporation of local public transport, can be incorporated in the future.

 

DAB is acknowledged as the standard in many industrial and emerging nations, and will gradually replace analogue systems in many countries.

 

DAB at Audi

 

Audi was the first car manufacturer to launch DAB successfully in the premium segment. It has been possible to enjoy the outstanding sound quality of the new digital radio standard since the start of this year in the A8 and A6 model series thanks to the quality of the sound systems installed. The Q7 will offer digital radio from the outset. Its functions are operated and displayed via the MMI (Multi Media Interface), either via the monochrome monitor for the basic version or via the colour TFT monitor for the high-end version of the MMI, in the Audi A8, A6 and Q7. The ensembles and their individual programmes are displayed.

 

In areas where there is no DAB reception, the MMI automatically switches over to the same station on FM and back to DAB as soon as it can be picked up again.

 

Most stations furthermore already transmit information to accompany programmes, such as details of the current track and artist, which can likewise be called up via the MMI.

In future, the information required in the vehicle will be supplied by further information and data services that are transmitted by DAB. Information such as news, weather forecasts and rail or air travel information will be available.

 

Surround sound via DAB

 

The film industry started using multi-channel recordings as long ago as the 1950s. But it was not until the 1970s that a surround method known as "Dolby Stereo" became established as the industry standard for space-filling film sound tracks. From the 1980s, the growing digitisation of audio and video media opened the door for further moves towards ever more authentic sound scenarios in the movie theatre. Following on from two, four and six channels, the standards for 14 channels have already been approved - and there is no end in sight to the race to introduce even more sound reproduction channels.

 

In the home environment, too, there is currently a shift from stereo towards multi-channel, in other words surround sound. Among suppliers, too, the trend is away from the distribution of purely stereo sources and towards the transmitting of multi-channel formats by satellite and cable. In parallel, picture and sound data carriers are being written with multi-channel information. A music DVD without a surround track is now scarcely accepted. The continuing spread of surround-compatible audio systems in the home, promoted by the success of the DVD with diverse surround sound formats, is also fuelling demand for multi-channel sound in the medium of radio. However, no satisfactory technical solution has yet been available.

 

DAB for the first time offers a fully digital chain of signals from the artist's microphone to the loudspeakers in the car. The customer benefits of the new system will be further enhanced in the future along with the introduction of source-encoded 6-channel surround sound on DAB.

 

Modern passenger cars often already satisfy the fundamental requirements for surround sound. For example, premium sound systems feature not only the obligatory front stereo speakers, but also rear speakers that can be used for the rear surround channels. Centre speakers and subwoofers are usually also present. The digital sound processor integrated into the amplifier then helps with signal processing and sound optimisation for the vehicle-specific reproduction of a surround signal.

 

The requirements facing DAB surround

 

The requirements to be met by a DAB surround technique are tough. It must always be compatible with existing DAB receivers and must not impair their playing characteristics.

For best results, it must be a genuine multi-channel technique that is supplied with channels received individually and reproduces them as faithfully as possible. The supplementary information required must be encoded in a bandwidth-saving manner in order not to inflate the transmission input and costs inordinately.

 

DAB surround, the technique

 

All the aforementioned requirements can currently be met with the new technique of "DAB surround", which will represent the next stage of DAB. The supplementary information required is keyed into the existing stereo data stream, though older DAB receivers will not evaluate the surround information and will consequently reproduce a normal stereo signal. The highlight of this technique is the economical way in which it handles the restricted channel bandwidth. Around a 10 percent increase in data is sufficient to generate a 6-channel surround signal from the 2-channel stereo signal. As the available bandwidth of an ensemble is limited, use of the new technique means for instance that only seven instead of eight audio programmes will be offered in an ensemble, but that these will then be in surround format.

 

The outstanding sound quality is assured by this alliance of ultramodern techniques of music encoding. The technological basis is a refined version of the music encoding method which became widely known as "MP3".

 

The benefits for the listener

 

The car is now regarded as an extension to a person's living space, and is often the only place where it is possible to listen to music undisturbed. It is only possible to make optimum use of the sound components already in the car with the aid of surround systems. This technique now permits more precise locating of sound sources and greater spatial acoustic depth than is possible with systems based on the traditional stereo signal.

 

Whereas the choice of sound carriers with recordings of genuine 6-channel surround was previously limited, the growing range of surround products will in future be delivered to the car "for free", at no additional input. Most radio stations are already prepared for multi-channel productions and are to some extent are already using them.

Audi Customers and electronics (Part 1)

Audi Electronics Centre as a process-chain building (Part 2)

Audi quality as the basis for success (Part 3)

Audi Electronics Venture GmbH (Part 4)

Audi Electronics Research Laboratory - Research in Silicon Valley (Part 5)

Audi Connectivity: integration and interfaces for multimedia (Part 6)

Audi transformation of the car into a mobile concert hall (Part 7)

Audi A8 Bang & Olufsen Advanced Sound System (Part 8)

Audi innovative solutions and future trends at the driver's workplace (Part 9)

Audi Driver Assistance (Part 10)