Digital Voice Systems VC-20-MR2, User Manual

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Section 2 – VC-20 AMBE™ Vocoder Board Overview
VC-20 AMBE™ Vocoder Board User’s Manual
page 5
The Speech Compression Specialists
D
IGITAL
V
OICE
S
YSTEMS,
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NC.
2 VC-20 AMBE™ Vocoder Board Overview
2.1 Advanced Multi-Band Excitation (AMBE

Vocoder)
The Advanced Multi-Band Excitation (AMBE

Vocoder) technology is based on
the Multi-Band Excitation (MBE) speech model. This speech model provides a
unique speech coding framework which results in a number of advantages over
linear prediction based speech coders such as CELP, RELP, VSELP, MELP,
ECELP, MP-MLQ, and LPC-10, etc. .
(1)
The AMBE

voice coder (vocoder) was first developed in the mid 1990’s by
Digital Voice Systems, Incorporated. This vocoder maintains speech intelligibility
and naturalness at rates as low as 2.4 kbits/sec. The AMBE

Vocoder system is
less complex than either CELP or VSELP, and therefore, it is easily integrated into
low-cost, low-power, communication integrated circuits.
2.2 VC-20 AMBE

Vocoder Board Basic Operation
Connections are made to the VC-20-MR2 using the attached DIN 41612 connector
which is described in Sections 4 and 5. The user must supply the VC-20-MR2 with
a 5v digital power supply and a +/-5v analog power supply. It is preferable to
decouple the analog supply from the digital supply by using separate power supplies.
The VC-20-MR2 contains one set of jumpers which is used to loop-back the encoder
signals to the decoder, and to enable the on-board clocks and frame signals. The pin
assignment for this jumper is documented in Section 6.
The VC-20-MR2 can be operated in loop-back mode by using the internal clock and
frame generator to generate the clock signals, TXCK and RXCK, and the frame
signals, FMEN and FMDE, as shown in Figure 2. Jumpers 1-12 on the fourteen pin
jumper block should be connected and all other jumpers should be disconnected.