Operation Manual

Standards Used by Alice
Alice – 4 How Alice Works 21
4.1 Standards Used by Alice
Alice uses the following standards:
Standard Description
H.320 An ITU (International Telecommunications
Union) standard. General term for all audio
and video transmission over ISDN.
H.323 An ITU (International Telecommunications
Union) standard. A package of standards for
audio and video transmission via IP
connections.
H.221 / H.225 These standards define the protocols with
which video and audio data is sent and
user-defined data is transmitted.
H.230 This standard defines audio and video
commands in the H.221 standard.
H.242 This standard defines how the B channels
are managed. It also describes the
protocols for establishing and clearing a
connection.
H.245 This standard defines a control channel
over which the properties of the connection
are negotiated.
H.261 Standard for video compression. H.261
supports the CIF and QCIF formats (see
below).
H.263 An improved standard for video
compression which requires less bandwidth
than H.261. H.263 also
supports the QCIF
and 4CIF formats (see below).
G.711 A standard for audio coding. In this
standard a bandwidth of 56 kBit/s is
required for transmission of the audio data.
A number of remote sites allow G.711 only
for transmission with two B channels
(128 kBit/s), so that enough bandwidth
remains available for the transmission of
video data.
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