Commnuications Standards
H.281 Far End Camera Control
Handles the control of remote cameras during videoconferences.

H.320 ITU-T CODEC
Recommendation that combines other recommendations for creating video phone system specifications.

Dual H.320
Protocol for simultaneous sending and receiving of video signals.

H.321
Describes ATM-based Local Area Networks (LANs)

H.322
Recommendation describing video phone systems and terminals for Local Area Networks with guaranteed bandwidth (Quality of Service). It directly refers to the IEE P802.9a draft concerning rapid-response-time LANs.

H.323
Recommendation describing video phone systems and terminals for Local Area Networks without guaranteed bandwidth (Quality of Service).

Top

Conection Standard
H.221
ITU-T – Recommendation concerning framework structure of audio-visual telecommunication services.

H.230CODEC
ITU-T CODEC recommendation for controlling frame synchronisation and control signals of audio-visual systems.

H.231
ITU-T MCU recommendation for bridges with channels of up to 2 Mbps.

H.242
ITU-T CODEC recommendation for systems enabling the connection of two audio-visual terminals using digital channels of up to 2 Mbps.

H.243
ITU-T recommendation: Procedure for establishing communication links between three or more audio-visual terminals with digital channels of up to 2 Mbps.

H.245
H.245 ITU-T recommendation: Control protocol for multimedia communication. Bonding mode 1.

Top

Image Transmission Standards
CIF
Common Intermediate, image resolution 352 x 288 pixels.

FCIF
see CIF

QCIF
Quarter Common Intermediate, image resolution 176 x 96 pixels.

SQCIF
Sub Quarter Common Intermediate, image resolution 128 x 96 pixels.

4xCIF
Common Intermediate for still image transmission, image resolution 704 x 576 pixels.

16xCIF
Common Intermediate for still image transmission, image resolution 1408 x 1152 pixels.

VGA/SVGA
image resolution of 640 x 480 pixels / 800 x 600 pixels

XGA/SXGA
image resolution of 1024 x 768 pixels / 1280 x 1024 pixels.

Top

Video
H.261
Annex D ITU-T CODEC recommendation for simultaneous transmission of image data in North America. Other areas can also use JPEG.

H.263
video encoding for transmission of audio-visual services a low transfer speeds. Greatly enhances the H.261 provisions by facilitating high-quality image transmission. The former standard only supported transfer of low-resolution images of credit card size. The H.263 standard is, for example, very useful in the area of medical teleworking.

H.263+
ITU-T recommendation for still images of 4xCIF resolution.

H.263++
ITU-T recommendation for two live images a resolution of 4xCIF.

Near TV
proprietary Polycom standard for video transmission in 16:9 format a 60 frames/sec.

ProMotion
proprietary PictureTel standard for video transmission a 50 frames/sec.

Top

Audio Standards
G.711
ITU-T recommendation for voice transmission a 3.1 kHz using bit rates of 48, 56 or 64 kbps.

G.722
ITU-T recommendation for voice transmission up to 7 kHz using bit rates of 48 or 64 kbps.

G.722.1
7 kHz audio bandwidth a a transmission speed of 16.24 or 32 kbps.

G.723
ITU-T recommendation for multimedia data transmission a 5.3 or 6.3 kbps.

G.723.1
ITU-T recommendation for voice transmission over the Internet using small bandwidths.

G.728
ITU-T recommendation for voice transmission at 3 kHz using bit rates of 16kbps.

PT716plus
proprietary advanced PictureTel standard for voice transmission at 7 kHz and 16, 24 or 32 kbps.

PT724
proprietary advanced PictureTel standard for voice transmission at 7 kHz and 24 kbps.

Siren 14
proprietary advanced PictureTel standard for voice transmission at 14 kHz and 24.32 or 48 kbps.

Acoustic Plus 716
Proprietary Polycom audio norm.

PSTN Audio
General term for voice transmission via public telephone networks.

Top

Compression Standards

MPEG
Motion Picture Experts Group. An ISO standard for video and audio compression supporting zero-loss and loss-prone compression. Is used for playing multimedia images from CD-ROM, for pay TV, broadcasting, and is also suited for video communication.

JPEG
Joint Photographic Experts Group. An ISO standard for compression, storage and transfer of diverse still image formats (not restricted to NTSC source). JPEG can be employed in conjunction with CODECs (coder/decoder)complying with the ITU-T standard. It supports zero-loss and loss-prone modes. The so-called “Motion-JPEG” is a proprietary motion picture transfer type – it is not a standard.

Huffman encoding
zero-loss encoding algorithm that describes the image data based on statistic functions. Data is compressed by having common data groups of short length represent less frequent data groups of greater size. Huffman encoding is employed by H.320 and other video communication CODECs as well as by the group-3 fax and the JPEG standard.

Top

Data Standards
T.120
A general ITU-T overview recommendation describing transfer protocols for multimedia data. It contains multi-layer protocols that greatly enhance multimedia, MCU and CODEC controlling capabilities. This enables advanced MCU operation well beyond the specifications of the H.231 and H.243 standards.

T.122
ITU-T recommendation describing multipoint communication services (MCS) for audio-graphical and audio-visual conferences.

T.123
ITU-T recommendation describing protocol stacks for audio-graphical and audio-visual teleconferencing applications. There is a current version and also a new draft (10/95).

T.124
ITU-T recommendation for controlling remote audio-graphical and audio-visual terminals.

T.125
ITU-T recommendation describing multipoint conference service specifications.