Specifications
Net-2000™ VCU Users Manual
Version 4.0, December, 2013
Interface Protocol
The
voice data format to synthesize is as follows:
The voice data to be synthesized is 16 bit PCM
(format & 0x000f) == 0x00
All other formats are invalid.
Soft Decision ONLY applies to the AMBE+™, AMBE+2™ , GMR-1 and GMR-2+ Vocoders. If channel[] contains
hard decision data (no soft decision error detection)
channel[i] == 0x01 is a one,
channel[i] == 0x00 is a zero
If 4 bit soft decision error detection is used then,
channel[i] == 0x0f is the most confident one
channel[i] = 0x00 is the most confident zero
Other values for the number of soft-decision bits are coded in a similar manner. For transmitting DTX frames a
channel data packet must contain all ones in the channel[] array. To signal no data and force a frame repeat the
channel[] array data packet must contain all zeros.
6.3.2.12 Channel Data Packet Bytes 28-219 (channel[0-191])
For simplicity, and since channel data packets are small compared to nominal Ethernet frames, all 192 channel bytes
are ALWAYS transmitted regardless of the actual bit-rate of the vocoder. Each byte of the channel [] array contains
one channel data “bit”.
Channel
[
192
]
16 bit Word
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Bytes
B
y
te
(
n
)
B
y
te
(
n+1
)
Parameter Name
… … … …
28 - 29 x x x x x x x x x x x x x x x x channel [0-1]
30 – 31 x x x x x x x x x x x x x x x x channel [2-3]
32 – 33 x x x x x x x x x x x x x x x x channel [4-5]
… … … …
218-219 x x x x x x x x x x x x x x x x channel [190-191]
Table 29 channel Parameter
6.3.3 Voice Data Packet
Voice Data Packets contain 8kHz sample rate 16 bit PCM voice data that are inputs to the VCU encoder or are
synthesized outputs of the VCU decoder. Encode Command Packets and Voice Response Packets use the Voice
Data Packet format.
6.3.3.1 Encode Command Packet
The VCU can receive an Encode Command Packet from a PC in File Mode. The VCU encodes the voice data and
responds by sending a Channel Response Packet to the PC.
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