| Narrow-band visual telephone systems and terminal equipment | |
| Status | Published |
|---|---|
| Year started | 1990 |
| Latest version | (03/04) March 2004 |
| Organization | ITU-T |
| Related standards | H.221, H.230, H.242, H.261, H.262, H.263, H.264, H.265 |
| Website | https://www.itu.int/rec/T-REC-H.320 |
H.320 or Narrow-band visual telephone systems and terminal equipment is an umbrella Recommendation by the ITU-T for running multimedia (audio/video/data) over ISDN based networks. The main protocols in this suite are H.221, H.230, H.242, audio codecs such as G.711 ( PCM) and G.728 ( CELP), and discrete cosine transform (DCT) video codecs such as H.261 and H.263. [1]
It is formally named as Narrow-band visual telephone systems and terminal equipment. It specifies technical requirements for narrow-band visual telephone systems and terminal equipment, typically for videoconferencing and videophone services. It describes a generic system configuration consisting of a number of elements which are specified by respective ITU-T Recommendations, definition of communication modes and terminal types, call control arrangements, terminal aspects and interworking requirements. [2]
The service requirements for visual telephone services are presented in ITU-T Recs F.720 for videotelephony and F.702 for videoconference. Video and audio coding systems and other technical aspects common to audiovisual services are covered in other Recommendations in the H.200/F.700-series.
Narrow-band for this specification is defined as bit rates ranging from 64 kbit/s to 1920 kbit/s. This channel capacity may be provided as a single B/H0/H11/H12-channel or multiple B/H0-channels in ISDN.
Used video codecs: H.261, and optionally H.262, H.263, H.264 according to the video hierarchy specified in specification, and in ITU-T Recs H.241 and H.242. H.261 is mandatory in any enhanced H.320 system with video capability. Baseline H.263 capability shall be required in systems that use enhanced video modes. [2]
Used audio codecs: G.711, and optionally G.722, G.728, G.723.1, G.729. (Example of usage: If a visual telephone interworks with a wideband speech terminal, G.722 audio may be used instead of G.711 audio.) [2]
See also
References
- ^ Davis, Andrew (13 June 1997). "The H.320 Recommendation Overview". EE Times. Retrieved 7 November 2019.
- ^ a b c ITU-T (2004-03) (PDF) H.320 : Narrow-band visual telephone systems and terminal equipment, Retrieved on 2009-07-21
External links
- ITU-T website
- ITU-T H.320 : Narrow-band visual telephone systems and terminal equipment - technical specification
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