
PSB 7230
Firmware Features
Semiconductor Group
141
Data Sheet 1998-07-01
In G.723 the natural frame length of 30 ms is split up into three 10 ms packets to fit into
the interface structure of the other audio modes. These packets are numbered by the
P(1-0) bits (in OPT1 for outband control, OPTIONS for inband control) taking on the
values 0, 1 or 2 for the first, second or third part of a 30 ms frame, respectively.
When entering G.723 mode the pipelining is similar to the above listing, but the first
G.723 packets from the JADE AN will be invalid (indicate by MSB of OPT1). As
mentioned above for synchronisation of input and output packets one has to wait for valid
packets from the JADE.
When in G.723 mode, mode changes will be recognized by the JADE with the beginning
of the first 10 ms packet. Thus, the control block for a mode change request should be
transmitted to the JADE during the previous 3rd packet exchange. After an exit from
G.723 encoder has been requested, the P(1-0) counter will no longer reflect the packet
numbers even during the phase of draining the JADE internal pipeline. See the
Example
below for details (high rate without voice activity detection used in this example,
behaviour for the other modes is similar). The recommended host procedure for setting
up G.723 encoding (and/or decoding) is as follows:
1.
Wait for status packet showing the desired mode. The firmware takes care that
the 4th packet after a mode change shows the desired mode
Wait for the 1st valid G.723 encoded packet numbered as packet #0. All
subsequent packets will be numbered correctly.
2.
Table 26
Packet#
(10 ms)
Control/Status Pipeline for G.723
Control (User to
JADE AN)
MODE OPT1* #Data
Bytes
00
00
0
Status (JADE AN to
User)
MODE OPT1 #Data
Comment
Bytes
0
1
00
00
Neutral status after Reset
2
66
00
0
00
00
0
Command: G.723 high rate
encode & decode
First (dummy) G.723
encoded data to JADE AN
for G.723 decoding
–
3
66
00
8
00
00
0
4
66
00
8
00
00
0
5
66
90
8
66
90
8
First (invalid) G.723
en-/decoded data from
JADE AN