DIGITAL RADIO GUIDE

bit

stream

super

framing demux

TERRESTRIAL TRANSMISSION SYSTEMS - DRM

DRM Source Decoding

AAC

Decoder

CELP

 

 

 

SBR

 

Audio

Decoder

 

 

 

Decoder

 

output

 

 

 

 

 

 

 

 

 

 

HVXC

Decoder

Extensive tests on these codecs at the sampling rates and resulting “bandwidths” have determined that AAC and especially AAC with SBR produce a perceived audio quality to listeners that is effectively the equivalent of monophonic FM in a 9 or 10 kHz channel. HVXC produces intelligible speech quality with bit rates of 2 to 4 kbps for HVXC and CELP produces excellent speech quality using around 8 kbps. All of these codecs are a part of the MPEG-4 audio standard.

SBR (Spectral Band Replication) is a special means of enhancing the perception of a spectrally truncated low band audio signal by utilizing, on a dynamic basis, the spectral content of the low band information to simulate the missing higher band behaviour. This requires about 2 kbps and therefore does not seriously subtract from a 20 to 25 kbps AAC output.

In concept, the technique is not complicated. Consider a violin as an example. A string stimulated by a bow and the placement of a finger on the string produces a fundamental frequency and harmonics characteristic of a violin. These frequencies can go as high as the audibility of the human ear – say somewhere between 15 and 20 kHz.

For a 9 or 10 kHz channel, the AAC sampling and processing of the violin’s output can only cover the lower part of the audio spectrum, for example not higher than 6 kHz. The SBR algorithm examines this lower band spectrum on a dynamic basis and infers what the “missing” higher audio frequency “harmonics” probably are. The level of re-inserted harmonics depends on the 2 kbps SBR helper signal which describes the shape of the spectral energy in the original signal before truncation for AAC coding stereo (which uses an additional 2 kbps of SBR). From the standpoint of a listener, the combined audio output sounds like 15 kHz audio rather than 6 kHz audio.

(4)Multiplexing, including special channels and energy dispersal

This section refers to the left side of Figure 4.1 through “energy dispersal”, not including the DI and audio/data encoding portions.

As noted in Figure 4.1, the DRM system total multiplex consists of 3 channels: the MSC, the FAC and the SDC. The MSC contains the services – audio and data. The

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Grundig Digital Radio manual DRM Source Decoding
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Digital Radio specifications

The Grundig Digital Radio represents a significant advancement in radio technology, combining aesthetics, functionality, and a user-friendly interface. As a pioneer in the audio and electronics industry, Grundig has successfully integrated modern digital capabilities into its traditional radio design, appealing to both nostalgic listeners and tech-savvy users.

One of the standout features of the Grundig Digital Radio is its versatility in reception. With DAB+ (Digital Audio Broadcasting) technology, users can enjoy a wide array of radio stations with superior sound quality, free from the hiss and interference commonly associated with analog broadcasts. The inclusion of FM and AM bands ensures that listeners are not limited, providing access to local stations that may not yet have transitioned to digital.

The Grundig Digital Radio is designed with ease of use in mind. Its intuitive interface, often featuring a clear LCD display, allows users to navigate through stations and settings effortlessly. Many models also include a built-in tuner that automatically scans and presets available stations, simplifying the setup process. For those who appreciate personalization, some variants come equipped with customizable presets, allowing users to save their favorite stations for quick access.

Portability is another key characteristic of the Grundig Digital Radio. Many models are lightweight and come with built-in handles, making them ideal for on-the-go listening, whether it's in the garden, on the beach, or during a picnic. Battery options, alongside mains power, ensure that users can take advantage of their radios wherever they choose.

In terms of sound quality, Grundig utilizes advanced audio technologies to deliver rich and clear sound. Enhanced bass responses and treble controls allow users to fine-tune their listening experience to match their preferences. Furthermore, many models feature additional inputs, such as AUX and USB ports, enabling users to connect their smartphones or other devices, expanding their audio options.

Other notable characteristics include built-in alarms and timers, which make the Grundig Digital Radio a versatile companion for daily routines. Some models even support Bluetooth connectivity, allowing for seamless streaming from a variety of devices.

In summary, the Grundig Digital Radio embodies the perfect blend of traditional radio appeal and modern digital technology, offering versatility, ease of use, superior sound quality, and portability to meet the diverse needs of today’s listeners. Its well-thought-out features and user-friendly design make it an excellent choice for anyone looking to enhance their audio experience.
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