
PSB 7238
Firmware Features
Semiconductor Group
149
Data Sheet 1998-07-01
d
decoding mute enable (1) and disable (0). After switching, a ramping function
is implemented to avoid audible clicks
e
encoding mute enable (1) and disable (0). After switching, a ramping function
is implemented to avoid audible clicks
Re(1-0),
Rd(1-0)
Restricted number of bits for encode and decode. Only used for G.722, that
offers modes where less than 8 bits per byte are used: 7 bits per byte
(56 Kbit/s) and 6 bits per byte (48 Kbit/s).
00
8 valid bits per byte
01
7 valid bits per byte
10
6 valid bits per byte
11
Reserved
G.723 uses these bits in a different way. When the encode mode is G.723
the Re bits give the desired encoding method:
00
High rate, don’t use silence suppression
01
High rate, use silence suppression
10
Low rate, don’t use silence suppresion
11
Low rate, use silence suppression
Rd is the same as the above, but indicates the mode of the data in this
packet. It is the same as the corresponding bits of the G.723 packet data.
S
Sampling Rate of the codec connected to the JADE, either 8 kHz (0) or
16 kHz (1). If the sampling rate of the codec is different from the sampling
rate expected by the selected speech coder, the JADE automatically uses
over-/undersampling filters to convert the audio data.
When using G.728 mode and S = 1 indicating a 16-kHz codec is connected,
the postfilter of G.728 is switched off to ensure the computational power for
the over-/undersampling filters is available. The effect on the audio quality is
negligible.
When using G.722 mode and S = 0 indicating an 8-kHz codec is connected,
the bandwidth of the G.722 input/output data is reduced to 3.4 kHz.
Nevertheless, the compressed data stream is fully compatible and
interoperable with the G.722 standard.