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DIGITAL RADIO GUIDE TERRESTRIAL TRANSMISSION SYSTEMS - DRM
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• MDI – Multiplex Distribution Interface: covers the transport of data and
commands from the DRM multiplexer to the DRM Modulator.
• MCI – Modulator Control Interface: covers the remote signalling of commands
and setups to the modulator and transmitter equipment.
• SDI – Service Distribution Interface: covers the transport of data and
commands from the studio and other sources to the DRM Multiplexer.
• RSCI – Receiver Status and Control Interface: covers the transport of receiver
status information in addition to the DRM multiplex as well as commands to
control the receiver’s behaviour.
(3) Audio Source Coding
Figure 4.2 depicts the variety of digital audio encoders in the DRM system – in
effect, AAC, AAC with SBR, CELP and HVXC – all of which can operate in a range
of bit rates, and consequently produce a range of audio quality. (See the ETSI
DRM standardization document ES 201 980 v2.1.1, 2004-06.)
The full range runs approximately from 2 kbps (HVXC minimum) to 25 kbps (AAC
maximum) within the 9/10 kHz channels for standard broadcasting in the
broadcasting bands below 30 MHz. HVXC and CELP are used for “speech only”
applications. AAC and AAC/SBR, within the permissible range, result in excellent
music and speech audio quality.
Figure 4.2: DRM Source Encoding and Decoding
SBR Encoder
(configuration
dependent)
AAC
Encoder
CELP
Encoder
Audio
super
framing
Audio-
signal
mux &
channel
coding
HVXC
Encoder
DRM Source Encoding