PSB7238 SIEMENS [Siemens Semiconductor Group], PSB7238 Datasheet - Page 155

• Manufacturer Part Number: PSB7238
• Description: Joint Audio Decoder-Encoder - Multimode
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Table 19
Packet#
(10 ms)
24.
25.
26.
27.
28.
The pipelining is identical for the 8 kHz pass-through mode.
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 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.
2.
Semiconductor Group
the 4th packet after a mode change shows the desired mode
subsequent packets will be numbered correctly.
Wait for status packet showing the desired mode. The firmware takes care that
Wait for the 1st valid G.723 encoded packet numbered as packet #0. All
MODE OPT1* #Data
02
00
00
00
00
Control/Status Pipeline for G.711 (identical for Pass-Through) (cont’d)
(User to JADE)
Control
00
00
00
00
00
Bytes
80
80
0
0
0
MODE OPT1 #Data
02
02
02
02
00
(JADE to User)
155
Status
00
00
00
00
00
Bytes
0
0
0
0
0
Comment
–
Command: Neutral Mode,
last G.711 data to JADE
–
Last G.711 A-law decoded
data from JADE
4th neutral packet, next can
change mode
Data Sheet 1998-07-01
Firmware Features
PSB 7238