PSB7238 SIEMENS [Siemens Semiconductor Group], PSB7238 Datasheet - Page 143

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

6.2.1.2
To minimize the bandwidth on the compressed audio interface, an outband controlled
protocol is implemented in the JADE. This means that the mode settings for the JADE
are usually done before audio data exchange is started using the procedure described
in Section 6.2.1.1. During audio data transfer the JADE keeps its current mode settings
and only compressed audio is exchanged.
The size and format of the compressed data is summarized in Table 18 below for the
various operating modes:
Table 18
Compression Mode
Neutral
8-kHz pass-through
16-kHz pass-through
G.711
G.722, 64 Kbit/s
G.722, 56 Kbit/s
G.722, 48 Kbit/s
G.728
G.723, 6.3 Kbit/s
G.723, 5.3 Kbit/s
1)
2)
In G.723 mode the natural frame size of 30 ms is split up into three 10 ms packets. To
simplify the protocol handling all different G.723 modes are transmitted with the same
data rate. Please refer to the following figure for sub-frame numbering with P(1-0) bits
and valid bytes per packet in the corresponding G.723 packets:
Semiconductor Group
Always the most significant bits of a byte are valid and the least significant bits are ignored.
All different G.723 packets are transmitted with the same number of bytes which is determined by the 6.3 Kbit/s
mode. This is to make the protocol simple, not to minimize the data rate. Please refer to the drawing below for
details
Compressed Audio Protocol with Outband Control
Compressed Data Packet
Size in Bytes
0
160
320
80
80
80
80
20
8
8
2)
143
Valid Bits per Byte
0
8
8
8
8
7
6
8
8
8
Data Sheet 1998-07-01
Firmware Features
PSB 7238
1)