Audio mode, function

D82.85-0117-79

Function requirements, audio mode, general

 Circuit 30g ON

 Transport mode not active

General information on the audio mode

The audio mode functions can be operated as follows:

 With the Audio/COMAND control panel.

The operation signals are transmitted from the Audio/COMAND control panel to the radio (Audio/COMAND) via the telematics CAN.

 Via the voice control system integrated in the radio (Audio/COMAND).

 With the multifunction steering wheel button groups.

The control signals of the multifunction steering wheel button groups are forwarded to the radio (Audio/COMAND) via the following route:

 Steering wheel electronics

 Steering wheel CAN

 Steering column tube module (MRM) control unit

 Chassis CAN

 Central gateway (CGW)

 User interface CAN

The audio mode consists of the following component functions:

 Function sequence for volume and sound settings

 Function sequence for radio mode function (FM/AM)

 Function sequence for playing and managing media

 Function sequence for Bluetooth®audio

Function sequence for volume and sound settings

All volume and tone settings are made via the radio (Audio/COMAND).

The volume and sound settings function is subdivided into the following subfunctions:

 Function sequence for manual volume and sound settings

 Function sequence for speed-dependent volume control (SDV [GAL])

Function sequence for manual volume and sound settings

Manually volume and tone settings can be selected as follows:

 The volume for the media sources is increased or decreased using the right multifunction steering wheel button group.

 The user can select the corresponding tone settings by selecting the "Sound" menu.

 The volume and tone settings are performed using the voice control system.

Function sequence for speed-dependent volume control (SDV [GAL])

The noise level in the vehicle interior is determined via the vehicle speed. The instrument cluster sends the data on vehicle speed over the user interface CAN to the radio (Audio/COMAND). Depending on this information, the radio (Audio/COMAND) raises or lowers the output level.

Function sequence for radio mode function (FM/AM)

The antennas receive signals for the FM (ultra-short wave), AM (medium wave (MW)), and short wave (SW) frequency bands - not in all national versions). The following useful signals relevant for the radio reception are modulated onto these signals:

 Music signals

 Speech signals

 Data signals (e. g. traffic information)

The AM and FM signals are received from the radio (Audio/COMAND) via the following route:

 FM/AM antenna

 Antenna amplifier

The radio mode function sequence consists of the following procedures:

 AM tuner function sequence

 Function sequence for FM double tuner with diversity reception (FM)

 Function sequence for radio data system (RDS)

AM tuner function sequence

For the MW and SW radio frequency bands, the useful signals are broadcast using amplitude modulation (AM).

Function sequence for FM double tuner with diversity reception (FM)

For the FM radio frequency band, the useful signals are broadcast using frequency modulation (FM).

Function sequence for radio data system (RDS)

In addition to the radio program, many radio stations (FM) also broadcast additional digital information such as station name, type of program and traffic message channel recognition. This information is evaluated by the radio (Audio/COMAND) and shown on the Audio/COMAND display control unit, if an RDS station is set and the "RDS" function is activated.

Function sequence for playing and managing media

 Explanations:
Secure Digital card = SD, Universal Serial Bus = USB

The following media sources are available for the audio mode:

 SD card via the memory card reader of the multimedia connection unit

 USB devices via the 2 USB connections of the multimedia connection unit

 CD or DVD via the drive integrated in the radio (Audio/COMAND)

 Media database

Audio files stored on an SD card can be shown on the Audio/COMAND display control unit by activating the "Memory Card" media source and played back by the radio (Audio/COMAND).

External devices (e.g. audio equipment, USB memory sticks, smartphones) can be connected to the USB connectors.

The CD or DVD drive is integrated in the radio (Audio/COMAND), and is read in by it.

For vehicles with COMAND Online, files can be saved in MP3-format or in a video format by an external media source on the hard drive integrated into the radio (Audio/COMAND) in a media database and then can be called up and managed at will. The media database offers 10 GB of memory.

Metadata are also stored along with the actual media files on a CD, DVD, SD card or a connected device. Metadata includes, e.g., the title, interpreter, composer, album, genre, audio book, podcast, file identifier, file type (audio or video). These metadata are evaluated by the radio (Audio/COMAND), i.e. a search engine integrated in the radio (Audio/COMAND) can be used to search for them.

For vehicles with COMAND Online, the metadata is collected in a memory, the media database. The radio (Audio/COMAND) permanently stores the meta data for up to three devices. When one of these devices is reconnected, the metadata is updated. As soon as a fourth device is connected, the oldest metadata record is overwritten.

Function sequence for Bluetooth®audio

The Bluetooth® antenna enables the radio (Audio/COMAND) to receive Bluetooth® audio signals from external devices. Bluetooth® audio is divided into the following additional information:

 Search for devices and authorization

 Connection and reconnection

 Metadata and display of information

Search for devices and authorization

The same options exist for the authorization of a Bluetooth® audio source as are available for telephony:

 Search via the device list

 External authorization

The device lists are set up the same for Bluetooth® audio and telephony. In the respective list, only those devices that support the corresponding Bluetooth® profile of the respective function are found or displayed during a search. With Bluetooth® audio, the Audio/Video Remote Control Profile (AVRCP) and Advanced Audio Distribution Profile (A2DP) are used. During telephony, the hands-free profile (HFP) is used. If a device supports both functions, it appears in both lists after authorization.

Connection and reconnection

If a device is connected that supports both HFP and AVRCP/A2DP, all profiles are connected. In this case the device is a telephone and the source of Bluetooth® audio at the same time.

When starting up, the radio (Audio/COMAND) searches for the last two telephones. If one of these devices is found, the radio (Audio/COMAND) connects to this device. If this telephone also supports AVRCP/A2DP, these profiles are also connected.

If a device is connected that only supports HFP, and a change is made to use "Bluetooth® Audio", the radio (Audio/COMAND) shows "Bluetooth audio equipment not connected", insofar as corresponding audio sources are listed in the device list.

The last used Bluetooth® audio source can be connected using the "Connect last device" function bar. However, the connection to the current telephone is interrupted here.

If a device that only supports AVRCP/A2DP is connected and a switch to the telephone application is then made, the connection to the device is disconnected, and the radio (Audio/COMAND) starts to search for the last two telephones.

Metadata and display of information

The display of information for Bluetooth® audio depends on the respective device used. If it supports AVRCP 1.0, only "Audio streaming" is shown on the Audio/COMAND display control unit and in the instrument cluster (IC) control unit. As of AVRCP 1.3, the track, album and artist are shown. In addition, the currently played time of the track can also be conveyed.

Function sequence for digital radio (DAB)

The DAB control unit enables the reception of digital radio in DAB format. The stations are categorized into groups in DAB, so-called "Ensembles".

With DAB reception, the radio (Audio/COMAND) transmits the FM station lists to the DAB control unit. If a comparable FM station is found, it is requested by the DAB control unit and the radio (Audio/COMAND) makes the FM audio signals available.

If DAB reception deteriorates, the system switches to the radio's (Audio/COMAND) FM station, whereby the DAB control unit adjusts the time lag between the digital and the analog signal. In this way the switchover is almost inaudible ("Seamless Linking").

For audio output via the speaker system, the DAB control unit transmits the audio signals to the radio (Audio/COMAND).

The DAB control unit is designed as a diversity tuner, and thus offers the following advantages:

 A background tuner collects the names of all available stations and ensembles for display on the Audio/COMAND display control unit.

 Display of "Electronic Program Guide" data on the Audio/COMAND display control unit (e.g. start and finish times of programs, if supported by the station).

 Faster switchover to another ensemble.

 Almost inaudible switchover between various ensembles with identical program (e.g. Deutschlandradio in various nationwide ensembles).

 Support of the extended audio codecs DAB+ and DMB audio (Digital Multimedia Broadcasting (DMB)), and thus reception of programs transmitted with these codecs.