Net-2000™ Voice Codec Unit
User’s Manual
Page 49
Section 3 – Net-2000™ VCU Control
DVSI Confidential Proprietary
Table 46 cmode Bits for Channel Response Packets
The AMBE/AMBE+ and AMBE+2 coders both support the DTMF_FRAME_FLAG.
The VAD flag is output by the AMBE+2 coder only to indicate that the frame contains voice or data,
the VOICE_ACTIVE flag is output by the AMBE+2 coder to indicate that the packet should be
transmitted to the decoder.
The AMBE/AMBE+ coder does not support the VAD flag and uses the VOICE_ACTIVE flag for that
function. The AMBE/AMBE+ coder does not have a flag to indicate whether the packet should be
transmitted. With the AMBE/AMBE+ coder you must transmit the first silence frame following a frame
with VOICE_ACTIVE set to do DTX.
The mu-law and A-law coders don't support any of these Channel Response Packet Flags.
Voice Response Packet
The Net-2000™ VCU transmits decoder data in Voice response packets (Table 47 Voice Response
Packet).
cmode parameter bits
Channel Response
Packet Flags
Byte 18
7 6 5 4 3 2 1 0
Byte 19
7 6 5 4 3 2 1 0
Bits
AMBE DTMF FRAME FLAG
If set, the encoder detected a tone and the data in
the channel[] array is a single, DTMF, or call
progress tone. The index and amplitude of the tone
should be put in the tone.idx and tone.amp
parameters of the packet, respectively.
1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
15
AMBE VAD FLAG
If set, the channel[] array contains voice data. If
cleared the channel[] array contains a silence frame.
0 0 0 0 0 1 0 0
0 0 0 0 0 0 0 0
10
AMBE VOICE ACTIVE FLAG
If set, the data in the channel[] array must be
transmitted to the decoder. If cleared, the data does
not need to be transmitted.
0 0 0 0 0 0 0 0
0 0 0 0 0 0 1 0
1
*Not Used
x * * * * x * *
* * * * * * x *
14, 13,
12, 11, 9,
8, 7, 6, 5,
4, 3, 2, 0