G.723.1
An audio codec that provides 4-KHz speech bandwidth switch able at 40, 32, or  or 24 kbps.
(See Codec.)
 
G.729
Both G.729 (compression at 8 kbps) and G.723 (compression to 5.3 kbps and 6.3 kbps)
have been defined as baseline voice compression coders to be used for audio
calls over an H.323 connection. Although the IMTC selected G.723, and the ITU
recommended G.729 for audio-only calls, both coders have the potential for
widespread deployment by VoIP vendors, including those developing PC telephony clients.
 
Codec
Coder/decoder. A device that converts (codes) analog voice signals into digital signals
for transmission and decodes them on reception.
 
H.323
H.323 is an International Telecommunications Union (ITU) standard for multimedia
communications (voice, video, and data) over connectionless networks that do not
provide a guaranteed quality of service, such as IP-based networks and the Internet.
It provides for call control, multimedia management, and bandwidth management for
point-to-point and multipoint conferences. H.323 mandates support for standard audio and video
codecs and supports data sharing via the T.120 standard. The H.323 standard is network,
platform, and application independent, allowing any H.323 compliant terminal to
interoperate with any other.
 
IP
Internet Protocol. Part of the TCP/IP family of protocols IP is the IETF
protocol used in the Internet. It describes software that tracks the Internet address
of nodes, routes data from its source to its destination, and recognizes incoming messages.
 
PSTN
Public Switched Telephone Network. The telephone network connecting all users.
 
QoS
Quality of Service. This measure can be either a network-oriented measure,
such as bit-error rate or QoS can be user-oriented, with measures
oriented toward the perceived quality received by the end user for audio,
video or multimedia applications.
 
VoIP
Voice over Internet Protocol. The transport of a real time
phone call over packet switching IP networks.