DWG2000 GSM/CDMA/WCDMA User
Manual
23
Copyright @ 2015
The API Server Address, API Server Port, User ID and API User Password on the above interface of
DWG2000 must be the same with the IP Address, Port, Auth ID and Password on the setting interface of
SMS Server.
Introduction to GSM Audio Coding
There are eight formats for GSM Audio Coding, including Auto, FR, HR, EFR, AMR_FR, AMR_HR, FR
and EFR, EFR and FR.
Auto
: it means GSM Audio Coding is automatic.
FR (Full Rate)
: the first digital speech coding
speech
standard used in the
GSM
digital mobile phone system.
The bit rate of the codec is 13 kbit/s, or 1.625 bits/audio sample (often padded out to 33 bytes/20 ms or 13.2
kbit/s).
HR (Half Rate)
: the bit rate of the codec is
6.5 kbit/s. It requires half the bandwidth of the
Full Rate
codec
and network capacity for voice traffic is doubled, at the expense of audio quality. It is recommended to use
this codec when the battery is low as it may consume up to 30% less energy.
EFR (Enhanced Full Rate)
:
is a speech coding standard that was developed in order to improve the quite
poor quality of
Full Rate
codec. Working at 12.2 kbit/s, the EFR provides good quality in any noise
conditions. The EFR is compatible with the highest
AMR
mode (both are
ACELP
). Although the EFR helps
to improve call quality, this codec has higher computational complexity, which in a mobile device can
potentially result in an increase in energy consumption as high as 5% compared to 'old' FR codec.
AMR (Adaptive Multi-Rate)
:
is an audio compression format optimized for speech coding. AMR
speech codec consists of a multi-rate narrowband speech codec that encodes narrowband (200–3400 Hz)
signals at variable bit rates ranging from 4.75 to 12.2 kbit/s with toll quality speech starting at 7.4 kbit/s.
There are two modes for the AMR codec in the DWG2000:
AMR_FR
:
the AMR codec in a full rate channel (FR)
AMR_HR
:
the AMR codec in a half rate channel (HR).
FR and EFR
: GSM Audio Coding supports both FR and EFR, but FR is prior to EFR.
EFR and FR
: GSM Audio Coding supports both EFR and FR, but EFR is prior to FR.\