Net-2000™ Voice Codec Unit
User’s Manual
Page 31
Section 3 – Net-2000™ VCU Control
DVSI Confidential Proprietary
seq
=
Sequence number*
Byte 4
7 6 5 4 3 2 1 0
Byte 5
7 6 5 4 3 2 1 0
Decimal
Value
Minimum Value
1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
-32768
Maximum Value
0 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
32767
Table 16 seq header parameter
Note:
Sequence numbers should be incremented by one every time a packet is
transmitted. When the sequence number reaches 32767, the next valid sequence
number is -32768.
Channel Packet Bytes 6 to 17 (rate[6])
There are six rate information words and four parameter words that are common to the Encoder
Command Packet, Decoder Command Packet, Voice Response Packet and the Channel Response
Packet. These are shown in Table 17.
rate [5] vocoder rate
Bytes
(msb-lsb)
Bit
7 6 5 4 3 2 1 0
Bit
7 6 5 4 3 2 1 0
Parameter Name
… … …
…
6 - 7
x x x x x x x x
x x x x x x x x
rate [0]
8 - 9
x x x x x x x x
x x x x x x x x
rate [1]
10 - 11
x x x x x x x x
x x x x x x x x
rate [2]
12 - 13
x x x x x x x x
x x x x x x x x
rate [3]
14 - 15
x x x x x x x x
x x x x x x x x
rate [4]
16 - 17
x x x x x x x x
x x x x x x x x
rate [5]
… … …
…
Table 17 Rate Channel Parameter
The six Rate words contain information of the vocoder and data/FEC rate details. The bottom 8 bits
of the rate [0] word contains the vocoder type. The rate [1-4] words will contain specific information
on the voice compression rate and FEC used. This information will vary for the different types of
vocoders.
Rate information can be decoded as follows:
the bottom 8 bits of rate[0] contains the source rate in bits-per-frame, 1 frame=20 ms.
the bottom 8 bits of rate[5] contains the total rate in bits-per frame
the top 8 bits of rate[5] specifies the vocoder type:
0xc0 : ambe/ambe+ (i.e. ambe2000)
0xc1 : ambe+2
0xc5 : mu-law
0xc6 : A-law
All others are reserved.