
PSB 7280
Semiconductor Group
149
Data Sheet 1998-07-01
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
Chapter 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 the table below for the
various operating modes:
Compressed Audio Protocol with Outband Control
Note: Independently of the interface selection for the compressed audio, always the
most significant bit of the most significant byte is transferred first, e.g. when using
pass-through modes, the 16-bit samples are split up into two bytes and the most
significant bit of the most significant byte is transferred first (big endian).
6.2.1.3
The following paragraph describes an H.221/H.223 oriented protocol which transfers the
control information inband with the compressed audio data.
The user sends commands and data, and the provider sends status and data.
Commands and data or status and data are grouped into blocks of 16-bit words.
Between the user and the JADE one data packet is transferred each way every 10 ms.
The packet, that is transferred from the video processor to the JADE - called “command
data” - consists of eight command words followed by the appropriate number of data
words for the current speech algorithm:
Compressed Audio Protocol with Inband Control
1)
Always the most significant bits of a byte are valid and the least significant bits are ignored.
Table 19
Compression Mode
Compressed Data Packet
Size in Bytes
0
160
320
80
80
80
80
20
Valid Bits per Byte
1)
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
0
8
8
8
8
7
6
8