| H.320 | |
|---|---|
| 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 orNarrow-band visual telephone systems and terminal equipment is anumbrella Recommendation by theITU-T for running multimedia (audio/video/data) overISDN based networks. The main protocols in this suite are H.221, H.230, H.242,audio codecs such asG.711 (PCM) andG.728 (CELP), anddiscrete cosine transform (DCT)video codecs such asH.261 andH.263.[1]
It is formally named asNarrow-band visual telephone systems and terminal equipment. It specifies technical requirements for narrow-band visual telephone systems and terminal equipment, typically forvideoconferencing andvideophone 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 optionallyH.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 optionallyG.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]
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