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Videoconferencing 2000: H.323's Year?
September 6, 1999 |
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The Algorithms and Protocol Suites Alias: Character string, sometimes in e-mail domain form, that can be passed to gatekeeper to join a conference or call an endpoint. CIF: Common Intermediate Format for video; 352x288 pixels. Optional under H.323. E.164: Phone number or extension compatible with North America dialing plan. Usually a four-digit designator to join a conference or call an endpoint. G.711: Low complexity (no compression), high-quality audio algorithm. 50 to 3,600 Hz. Uses 48 to 64 Kbps. G.722: Medium complexity, high-quality audio algorithm. 50 to 6,000 Hz. Uses 48 to 64 Kbps. G.723: Medium complexity, medium-quality audio algorithm. 50 to 6,000 Hz. Uses 6.3 or 5.3 Kbps. G.728: Very high complexity, high-quality audio algorithm. 50 to 3,600 Hz. Uses 16 Kbps. H.320: ITU standards suite primarily for videoconferencing over ISDN circuits. H.323: Newer ITU standards architecture that adds options for operating over TCP/IP packet networks and analog telephone circuits. H.261: Standard discrete cosine transform compression algorithm required under H.320. Also recommended under H.323 if sufficient bandwidth is available. H.263: Similar, more aggressive compression algorithm. Optional under H.323 for low bandwidth conditions. QCIF: Quarter Common Intermediate Format for video; 176x144 pixels. Required under H.323. RAS: Registration/Admissions/Status information traded between H.323 endpoints and gatekeepers. Provides IP address, alias and E.164 identity.
T.120: Standards suite for data collaboration. Note this does not cover application sharing, which is implemented differently by various manufacturers.
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