H.320 is an umbrella recommendation by the ITU-T

ITU-T

The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....

 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

G.711

G.711 is an ITU-T standard for audio companding. It is primarily used in telephony. The standard was released for usage in 1972. Its formal name is Pulse code modulation of voice frequencies. It is required standard in many technologies, for example in H.320 and H.323 specifications. It can also...

, and video codecs such as H.261

H.261

H.261 is a ITU-T video coding standard, ratified in November 1988. It is the first member of the H.26x family of video coding standards in the domain of the ITU-T Video Coding Experts Group , and was the first video codec that was useful in practical terms.H.261 was originally designed for...

 and H.263

H.263

H.263 is a video compression standard originally designed as a low-bitrate compressed format for videoconferencing. It was developed by the ITU-T Video Coding Experts Group in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T.H.263...

.

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

Videoconferencing

Videoconferencing is the conduct of a videoconference by a set of telecommunication technologies which allow two or more locations to interact via two-way video and audio transmissions simultaneously...

 and videophone

Videophone

A videophone is a telephone with a video screen, and is capable of full duplex video and audio transmissions for communication between people in real-time...

 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.

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.262

H.262 or MPEG-2 Part 2 is a digital video compression and encoding standard developed and maintained jointly by ITU-T Video Coding Experts Group and ISO/IEC Moving Picture Experts Group . It is the second part of the ISO/IEC MPEG-2 standard...

, 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.

Used audio codecs: G.711, and optionally G.722

G.722

G.722 is a ITU-T standard 7 kHz wideband speech codec operating at 48, 56 and 64 kbit/s. It was approved by ITU-T in November 1988. Technology of the codec is based on sub-band ADPCM ....

, G.728

G.728

G.728 is an ITU-T standard for speech coding operating at 16 kbit/s. It is officially described as Coding of speech at 16 kbit/s using low-delay code excited linear prediction....

, G.723.1

G.723.1

G.723.1 is an audio codec for voice that compresses voice audio in 30 ms frames. An algorithmic look-ahead of 7.5 ms duration means that total algorithmic delay is 37.5 ms...

, G.729

G.729

G.729 is an audio data compression algorithm for voice that compresses digital voice in packets of 10 milliseconds duration. It is officially described as Coding of speech at 8 kbit/s using conjugate-structure algebraic code-excited linear prediction .Because of its low bandwidth requirements,...

. (Example of usage: If a visual telephone interworks with a wideband speech terminal, G.722 audio may be used instead of G.711 audio.)

External links

• ITU-T website
• ITU-T H.320 : Narrow-band visual telephone systems and terminal equipment - technical specification