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These are standards set by the ITU-T governing the transmission of video and communication compatibility.
H.221 ITU-T Recommendation regarding frame structure for audiovisual teleservices.
H.223 ITU-T Recommendation: Multiplexing Protocol for Low Bitrate Multimedia Communication;
H.230 ITU-T
codec Recommendation regarding frame-synchronous control and indication signals for audiovisual systems.
H.231 ITU-T MCU Recommendation for multipoint control units using channels up to 2 Mbps.
H.242 ITU-T codec Recommendation regarding: System for Establishing Communication Between AudioVisual Terminals using Digital Channels up to 2 Mbps.
H.243 ITU-T Recommendation: Procedures for Establishing Communication Between Three or More AudioVisual Terminals using Digital Channels up to 2 Mbps.
H.245 ITU-T Recommendation; Control Protocol for Multimedia Communication.
H.261 ITU-T codec Recommendation regarding a video codec for audiovisual services at p x 64 Kbps. Regrettably, motion compensation and field sub-sampling (loop filter) are implementation optional in the standard. Users considering an ITU-T codec for operation at bit rates of 384 Kbps or below should ensure that the manufacturer has implemented these options.
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, Video Coding for Low Bitrate Communication; regarding a video codec for audiovisual services. Considerably broadens H.261 capabilities, extending from low- resolution, credit card-size images, to high-quality, exceptional detail images, for applications such as telemedicine. Backward compatibility to H.320 QCIF(Quarter Common Intermediate Format) and, optionally, to CIFand SQCIF (Sub-QCIF) is provided.
H.320 A series of audio visual communications recommendations which were ratified by the CCITT in December 1990. The aim of the series, which applies to audio visual communications over 56/64 Kbps to 2.048 Mbps channels, is to ensure videoconferencing systems and video terminals will interconnect across any network. H.320 is an umbrella standard encompassing a series of recommendations, including:
  • H.221 (frame structure for a 64-1920Kbps channel);
  • H.230 (frame synchronous control and indication signals);
  • H.242 (systems for establishing communications between audio visual terminals using digital channels up to 2 Mbps);
  • H.261 (visual coding for transmission over 56/64-2048 Kbps digital channels);
  • G.711 (An ITU-T Recommendation detailing a 32- to 64-Kbps 3.4-KHz bandwidth audio coding algorithm);
  • G.722 (An ITU-T Recommendation detailing a 64-Kbps 7-KHz bandwidth audio coding algorithm. Part of the ITU-T codec requirements);
  • G.728 (An ITU-T Recommendation detailing a 16-Kbps 3.4 KHz bandwidth audio coding algorithm);
H.321 ITU-T Recommendation describing ATM-based LANs.
H.322 ITU-T Recommendation describing: Visual Telephone Systems and Terminal Equipment for Local Area Networks which Provide a Guaranteed Quality of Service [guaranteed bandwidth]. This standard makes direct reference to the Draft IEEE P802.9a (which see). These standards describe LANs which provide low latency, suitable for videoconferencing.
H.323 ITU-T Recommendation describing: Visual Telephone Systems and Terminal Equipment for Local Area Networks which Provide a NON- Guaranteed Quality of Service
H.324 (suite spec.) ITU-T Recommendation describing a Terminal for Low Bitrate 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 and exceptionally good multipoint support and continuous presence are also provided.
Health Care Information Infrastructure (HCII)
A subset of the NII, expected to save the U.S. in the neighborhood of $100 billion given that information processing alone amounts to approximately 20 percent of health care costs. HCII is expected to save health care costs through development of the following delivery systems:
  • administrative information systems (HIS) clinical information systems (CIS)
  • telemedicine
  • personal health information systems (CHINs).
The evolution of HCII will require development of four main segments of the current telecommunications infrastructure:
1.transmission lines, i.e., cable TV (CATV) and telephone companies. 2.microwave
SEE ALSO Medical Informatics.

Health Level-7 Data Communications Protocol (HL-7)
Defines standards for transmitting data for billing, hospital census, order entries, and results reporting over hospital networks. The protocol is accepted by most types of host computers. HL-7 allows bedside terminals, radiological image stations, patient accounting, order entries, and critical care monitors to be incorporated into a single system. SEE ALSO CPR and Medical Informatics.

Health Open Systems Trials (HOST)
A project funded by the National Library of Medicine (NLM) to develop telemedicine demonstration projects that evidence an Open Systems approach. Major partners include IBM and Sprint.

Health Services Technology Assessment Text (HSTAT)
HSTAT is an NIH initiative to develop national standards of clinical care.

High-Definition TeleVision (HDTV)
Any of a number of television standards providing an aspect ratio of about 2:1 and resolution far superior to PAL or NTSC.

High Density TeleVision (HDTV)
High resolution broadcast video. See MPEG-2. Vertical resolution about 4 times that of a standard television (1,125 lines compared to 352 lines in a standard NTSC television output) and an aspect ratio of 16:9, similar to a movie screen.

High pass filter See
low pass filter

High resolution still imagery
Still photographs taken with a digitizing camera, compressed into a storm JPEG format, transmitted via satellite and/or telephone lines, decompressed and processed in a digital film printer at 200 dots/sq inch.Quality and color better than regular still photographs. Especially useful for dermatology telemedicine consults.

Hospital Information System (HIS)
Provides support for all information processing within the organization with a focus on adminstrative support (e.g. planning and budgeting, marketing, personnel, etc.) It integrates the clinical information system with strategic planning and quality improvement. There is development underway to apply hypertext technology (such as this document) to Hospital Information Systems. One example is remote reading and interpretation of radiographic studies (RIS). For more explanation of this concept, read WWW and the Electronic Medical Record.

Provides a cost-effective single point of connection to the network for workstations and other devices.

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.320and other videoconferencing codecs, Group 3 facsimile and JPEG.

Human Interface
Human-computer interface technologies make it possible for human beings to get understandable information in to or out of computers. These can be as basic as a keyboard and mouse or as complicated as speaking to and computer and being understood--or receiving a dynamically generated, animated video/audio presentation of on-line information as an answer to a question. The technologies include: graphical user interfaces, animation and full-motion video, optical character recognition (OCR), handwriting recognition, speech (synthesis and recognition) and natural language (particularly translation)

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