What Is Codec - ZyXEL Communications P-2602HWNLI Support Notes

What is codec?

Codec is an algorithm which converts analog signal into digital signal and vice versa. There are three main
types of waveform codec, source codec, and hybrid codec. Each consume different amount of bandwidth and
provide different voice quality level.
What is the relation of codec and VoIP?
As VoIP is general term send voice information in digital form in discrete packets over digital network and this
digital network is public network, thus there maybe other packet such data packet uses network at the same time.
The codec choose is related to how much bandwidth voice packet will consume. In bandwidth-wise aspect the
smaller amount of bandwidth used the better. But in voice aspect the higher quality the better.
What codec does Prestige support?
Prestige supports the following commonly used codec.
• G.729 voice codec
• G.711u-law voice codec
• G.711a-law voice codec
Note: G.711 u-law or G.711 a-law is country specific, thus ZyXEL device is shipped preconfigured to use u-law
or a-law according to specific country. If for special reason this setting needed to be changed. It can be
modify through device CI command through telnet. For the command please refer to the CI command list in
the firmware release note.
Which codec should I choose?
As which codec choose is depending on what codec is supported on both end of the VoIP host. Generally a
codec with low bandwidth consumption and high voice quality is a good codec.
What do I need in order to use SIP?
The minimum required to use VoIP is as follow.
1. A high-speed Internet connection. This can be a cable modem, or a high-speed network services such as
ISDN, DSL or a T-1 link. The need of the bandwidth required will depend on the amount of telephone traffic
will be in your network.
All contents copyright (c) 2006 ZyXEL Communications Corporation.
P-2602HWNLI Support Notes
171