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H

H

Horizontal.

H.221

ITU-T recommendation regarding frame structure for audiovisual teleservices operating between 64 kbps and 1920 kbps.

H.222.1

ITU-T recommendation regarding multimedia multiplex and synchronization for audio-visual communication in an ATM environment.

H.223

ITU-T recommendation describing a multiplexing protocol for low bit rate multimedia cCommunication. Annexes include considerations for mobile and other high error rate environments.

H.224

ITU-T recommendation regarding a real-time control protocol for simplex operation using H.221 LSD, HSD and MLP channels.

H.230

ITU-T codec recommendation regarding frame-synchronous control and indication signals for audio-visual systems.

H.231

ITU-T MCU recommendation for multipoint control units using audio-visual channels up to 1920 Kbps.

H.233

ITU-T recommendation regarding a confidentiality system for audio-visual services.

H.234

ITU-T recommendation regarding encryption key management and authentication system for audiovisual teleservices.

H.235

ITU-T recommendation regarding security and encryption for H.323 and other H.245 based multimedia terminals.

H.241

ITU-T recommendation regarding extended procedures and control signals for H.300-series terminals.

H.242

ITU-T codec recommendation regarding a system for establishing communication between audio-visual terminals using digital channels up to 2 Mbps.

H.243

ITU-T recommendation defining procedures for establishing communication between three or more audio-visual terminals using digital channels of up to 1920 Kbps.

H.244

ITU-T recommendation regarding synchronized aggregation of multiple 64 or 56 Kbps channels (a.k.a. BONDING).

H.245

ITU-T recommendation setting out a control protocol for multimedia communication.

H.248.x

A series of 35 ITU-T recommendations regarding various forms of gateway control protocols.

H.261

ITU-T recommendation regarding a video codec for audio-visual services at p x 64 Kbps. Note that motion compensation and field sub-sampling (loop filter) are implementation-optional in the standard. Users considering the H.261 codec at bit rates of 384 Kbps or below should verify that the manufacturer has implemented these optional aspects.

H.261 Annex D

ITU-T codec recommendation for simultaneous graphics transmission in the North American region. Other administrations may use JPEG.

H.263

ITU-T recommendation regarding a video codec for audio-visual services, video coding for low bit rate communication. Considerably broadens H.261 capabilities, extending from low- resolution, credit card-size images, to high-quality, exceptionally detailed images for applications such as telemedicine. Backward compatibility is provided with H.320 QCIF (Quarter Common Intermediate Format) and optionally to CIF and SQCIF (Sub-QCIF).
 
The following table compares H.320 and H.324 video capabilities:

 

Picture Format	Luminance Pixels	Video Modes
		H.320/H.261	H.324/H.263
SQCIF	128H x 96V	O	R
QCIF	176H x 144V	R	R
CIF	352H x 288V	O	O
4CIF	704H x 576V	-	O
16CIF	1408H x 1152V	-	O

Where:
S = Sub, Q = Quarter, H = Horizontal pixels, V = Vertical pixels,
R = Required, O = Optional and, - = Not Defined.

H.262

ITU-T recommendation regarding advanced video coding for high-quality applications. This standard is the result of the merging of the ISO/IEC MPEG2 (which see) work and the ITU-T H.262.

H.264

ITU-T recommendation regarding advanced video coding for high-quality motion video applications. This standard is the result of the merging of the ISO/IEC MPEG4 Part 10 AVC and the ITU-T H.26L committees, to avoid duplication of parallel development efforts. In general, H.264 provides quality superior to MPEG2 at about 30 per cent of the bit rate or less. It is expected to fully replace MPEG2 over time.

There are two significant versions of H.264: Level 3 provides for mainstream video while Level 4 focuses on HDTV. Significant changes from MPEG2 include 4x4 PEL block-size and what is called foreground-background video coding.

H.281

ITU-T recommendation regarding far-end camera control protocol for videoconferencing using H.224.

H.282

ITU-T recommendation regarding remote device control protocol for multimedia applications.

H.310

ITU-T recommendation regarding broadband audio-visual terminals and communication systems.

H.320 (suite spec.)

ITU-T codec recommendation bringing together other recommendations to produce an overall visual telephony system specification including terminal equipment operating over a narrow bandwidth between 56 Kbps and 1920 Kbps.

H.321

ITU-T recommendation describing adaptation of H.320 to an ISDN n times ISDN B-channel environment.

H.322

ITU-T recommendation describing visual telephone systems and terminal equipment for local area networks that provide a guaranteed quality of service (guaranteed bandwidth). This standard makes direct reference to the Draft IEEE P802.9a, (which see). These standards describe low latency LANs, suitable for videoconferencing (Iso-Ethernet).

H.323 (suite spec.)

ITU-T recommendation describing packet-based visual telephone systems and terminal equipment for local area networks that provide a non-guaranteed quality of service. Includes multiple annexes.

H.324 (suite spec.)

ITU-T recommendation describing a terminal for low bit rate multimedia communication; includes various recommendations including video codec for low-speed connections using single or dual V.34 connected to analog POTS, plus ISDN, ATM and probably mobile, bringing together other recommendations to produce an overall visual telephony system specification. Some compatibility with H.320, network transcoding, exceptionally good multipoint support and continuous presence are also provided.

HDB3

High Density Bipolar 3. Zero suppression scheme used for signals transmitted over E1 links, similar to B8ZS and is based on AMI. A European digital network transmission line protocol allowing information and control data to both be embedded in the transmission bit stream.

HDLC

ISO: High-level Data Link Control protocol.

HDSL

High bit-rate Digital Subscriber Line, requiring two pairs, it can provide full duplex 1.544 Mbps over a distance of 3.65 Km (2.25 miles), mimicking a T1 line. This type of DSL does not support simultaneous telephony over the same physical wires. HDSL is a good choice for applications like videoconferencing requiring symmetrical communication links.

HDTV

High-Definition TeleVision. Any of a number of television technologies providing an image aspect ratio of about 2:1 (WxH) and with horizontal and vertical resolution far superior to NTSC, PAL or SECAM.

HTML

HyperText Markup Language, a subset of SGML, commonly used for Internet Web-page design.

HTTP

HyperText Transport Protocol, the method used for Internet domain addressing.

Huffman Coding

A lossless, statistically-based entropy coding technique used to compress data in which the most frequently occurring code groups are represented by shorter codes, and rarely occurring code groups are represented by longer codes. Used in H.320 and other videoconferencing codecs, Group 3 facsimile and JPEG.

Hz

Hertz, analog usage, cycles per second.

To use the glossary, click on the first letter of the term of interest:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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