H.323 Standards

H.323 Standards

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What standards apply to H.323?
Where do standards come from?
Why isn't the document I need available on this site?
Documents available for download

What standards apply to H.323?

Call signallng and control

H.323 - the standard describing videoconferencing over local area networks.
H.225 - call control protocol
H.235 - security
H.245 - media control protocol
Q.931 - digital subscriber signalling

Audio codecs

G.711 - PCM audio codec 56/64 kbps
G.722 - audio codec for 7 Khz at 48/56/64 kbps
G.723 - speech codec for 5.3 and 6.4 kbps
G.728 - speech codec for 16 kbps
G.729 - speech codec for 8/13 kbps

Video codecs

H.261 - video codec for >= 64kbps
H.263 - video codec for < 64kbps

Related standards

H.320 - The original ISDN videoconferencing standard.
H.324 - An extension of H.320 for videoconferencing over PSTN lines
T.120 - Real time data conferencing protocol

Where do standards document come from?

The documents covering the H.323 protocol suite are created mainly by the International Multimedia Teleconferencing Consortium (IMTC) and are distributed by the International Telecommunications Union (ITU).

The membership of the IMTC covers most of the big telcos and companies, and membership is "open" to anyone who can afford the $US6000 per year membership fee.

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Why isn't the document I need available for download?

There are three good reasons why the document you want may not be available:

The ITU charges between $US20 and $US100 for any standards document. Someone has to pay for it...
Documents cannot be freely distributed.
Once the IMTC has decided upon a standard, it must be ratified by the ITU and then made available. This may take many months.

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