Net-2000™ Voice Codec Unit
User’s Manual
Page 42
Section 3 – Net-2000™ VCU Control
DVSI Confidential Proprietary
Voice Packet Parameters
Voice Packet Bytes 0 &1 (len)
The len parameter (bytes 0 and 1) hold the 16-bit length of the packet (Table 3). The packet length
can vary from 344 to 348 bytes.
len
=
Length (in bytes) of total packet (including header)
Byte 0
7 6 5 4 3 2 1 0
Byte 1
7 6 5 4 3 2 1 0
Decimal Value
Data Packet Size
0 0 0 0 0 0 0 0
x x x x x x x x
344 - 348 bytes
Table 29 len header parameter
Voice Packet Bytes 2 & 3 (type)
The type parameter (bytes 2 and 3) is 16-bits packet type and is always 0x002 for voice data.
type
=
Packet type
Byte 2
7 6 5 4 3 2 1 0
Byte 3
7 6 5 4 3 2 1 0
Hex Value
Voice Data
0 0 0 0 0 0 0 0
0 0 0 0 0 0 1 0
0x0002
Table 30 type header parameter
Voice Packet Bytes 4 & 5 (seq)
Bytes 4 and 5 hold the 16-bit sequence number (see Table 5). The sequence number is used as a
method to detect if and when data packets are dropped, so it is important to ensure that consecutive
sequence numbers are transmitted for channel data packets during operation.
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 31 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.
Voice Packet Bytes 6 – 15 (rate[5])
The
rate[]
array is used to indicate the vocoder type and is identical to the
rate[]
array in the
Channel packet discussed in the previous section.
Voice Packet Bytes 18 & 19 (cmode)
The cmode element of the packet contains the input flags to the encoder when it is transmitted to the
VCU and the output flags of the decoder when it is transmitted from the VCU. The value of cmode