Digital Voice Systems Net-2000-P25, Руководство пользователя

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Net-2000™ Voice Codec Unit
User’s Manual
Page 19
DVSI Confidential Proprietary
Section 4 – Net-2000™ VCU Interface Protocol
The AMBE APCO coder runs in either one of two rates. The Full-Rate at 7200 bps including 4400
bps voice and 2800 FEC. The Half-Rate coder runs at 3600 including 2450 data and 1150 FEC.
rate [5] vocoder rate
rate [0] Packets
Byte 6
7 6 5 4 3 2 1 0
Byte 7
7 6 5 4 3 2 1 0
Hex
Value
APCO Full-Rate Vocoder (7200bps) 0 0 0 0 0 0 0 0 1 1 0 0 0 0 1 0 0x00C2
APCO Half-Rate Vocoder (3600bps) 0 0 0 0 0 0 0 0 1 1 0 0 0 0 1 1 0x00C3
APCO Half-Rate V Bit Stealing
(3600 bps)
0 0 0 0 0 0 0 0 1 1 0 0 0 1 0 0
0x00C4
Table 11 Vocoder Rate Parameter
For the APCO Full-Rate vocoder
(rate[0] & 0x00ff) == 0x00c2
For the APCO Half-Rate vocoder
(rate[0] & 0x00ff) == 0x00c3
For the APCO Half-Rate vocoder with bit-stealing
(rate[0] & 0x00ff) == 0x00c4
cmode
The cmode element of the Channel packet contains the input flags to the decoder when it is
transmitted to the VCU and the output flags of the encoder when it is transmitted by the VCU. The
value of cmode also depends on the vocoder in use. Tables 12a and 12b list values for the decoder
input and encoder output flags of the Channel packet.
Cmode parameter
Decoder Input Flags
Byte 16
7 6 5 4 3 2 1 0
Byte 77
7 6 5 4 3 2 1 0
Hex Value
Nominal Value 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0x0000
Lost Frame 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0x0004
Mute 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0x0008
Tone Signaling 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0x4000
Table 12a. cmode Parameter (Decoder Input Flags)
The nominal value for the cmode parameter should be zero when transmitting Channel packets to
the VCU. To get the decoder to perform a frame repeat set the Lost Frame flag. To generate
comfort noise (i.e., mute) set the Mute flag. The Tone Signaling Flag can be set to get the APCO
Half-Rate vocoder to ignore the channel data in the packet and generate a tone. The index and
amplitude of the tone should be set in the
tone[]
parameter of the Channel packet. The Standard
APCO decoder does not support tone signaling and ignores this flag.
Cmode parameter
Half-Rate Encoder Output Flags
Byte 16
7 6 5 4 3 2 1 0
Byte 77
7 6 5 4 3 2 1 0
Hex Value
Voice Active 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0x0002
VAD 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0x0400
Tone Frame 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0x8000