Specifications

MyPBX SOHO Administrator Guide
113/204
each other directly, bypassing the system. It is not always possible for the system to
negotiate endpoint-to-endpoint media routing.
3) Codecs
Figure 6-61
A codec is a compression or decompression algorithm used in the transmission of voice
packets over a network or the Internet.
u-law: A PSTN standard codec, used in North America, which provides very good voice
quality and consumes 64kbit/s in each direction (receiving and transmitting) of a VoIP call.
a-law: A PSTN standard codec, used outside of North America, which provides very good
voice quality and consumes 64kbit/s in each direction (receiving and transmitting) of a
VoIP call.
GSM: A wireless standard codec, used worldwide, that provides adequate voice quality
and consumes 13.3kbit/s in each direction (receiving and transmitting) of a VoIP call.
GSM is supported by many VoIP phones.
SPEEX: Speex is an Open Source/Free Software patent-free audio compression format
designed for speech. The Speex Project aims to lower the barrier of entry for voice
applications by providing a free alternative to expensive proprietary speech codecs.
Moreover, Speex is well-adapted to Internet applications and provides useful features that
are not present in most other codecs.
G.722:G.722 is a wideband speech coding algorithms which supports the bit rate of 64, 56
and 48kbps wideband. It’s a broadband voice encoding of G series.
G.726: A PSTN codec, used worldwide, that provides good voice quality and consumes
32kbit/s in each direction (receiving and transmitting) of a VoIP call. G.726 is supported by
some VoIP phones.
ADPCM, G.729A, H261, H263, H263p, H264, MPEG4.
Note: If you would like to use G.729, please enter your license.