H.320 - Umbrella standard that references audiovisual conferencing protocols and procedures required for narrow-band visual telephone services. This recommendation also includes the audio coding recommendations that are used to encode, transmit and decode audio signals in association with video data.
H.221 - Defines the frame structure required for videoconferencing. This recommendation also defines the multiplexing scheme used to combine video, audio, data and control information on a single 64 kbps channel, as well as the aggregation of multiple individual channels for higher transfer rates.
H.230 - Defines communication control signals including Frame Synchronous control and Indications signals for audiovisual systems.
H.231 - Defines the minimum requirements for Multipoint Control Units (MCU) by describing the means by which three or more audiovisual terminals communicate simultaneously.
H.242 - Defines the sequences used when connecting two or more compliant terminals in a single conference where audio, video and data modes are exchanged and negotiated before communications can occur.
H.243 - Defines the sequences used when connecting three or more video CODECS in a single conference. The connection of one MCU to another MCU is also defined within the H.243 recommendation.
H.261 - Comprised of video signal digitalization and compression methods. The standard defines how to encode and decode video as information flows between the MCU and recipient terminal.
H.263 - Specifies a coded representation that can be used for compressing the moving picture component of audiovisual services at low bit rates. The basic configuration of the video source coding algorithm is based on Recommendation H.261 and is a hybrid of inter-picture prediction to utilize temporal redundancy and transform coding of the remaining signal to reduce spatial redundancy. The source coder can operate on five standardized picture formats: sub-QCIF, QCIF, CIF, 4CIF and 16CIF. The decoder has motion compensation capability, allowing optional incorporation of this technique in the coder. Half pixel precisions is used for the motion compensation, as opposed to Recommendation H.261 where full pixel precision and a loopfilter are used. Variable length coding is used for the symbols to be transmitted.
T.120 - A standard for audiographics exchange. The suite of T.120 data and graphics conferencing standards compliment the H.320 umbrella standard for audiovisual conferencing protocols.
G.711 - Standard encoding method that is used in 4 khz analog telephone signals digitized through a digital network. Such rates vary in a videoconferencing environment ranging from 56 to 48 kbps depending on network capabilities.
G.722 - Standard encoding method that is used to convert a 7 khz analog audio sample into a 56 kbps digital channel.
G.722 - is used in applications where audio quality is important.
G.728 - Recommendation for the coding of speech at 16 kbits/sec using Low-Delay Excited Linear Prediction (CELP) producing audio quality comparable to a G.711 signal. However, only 16 kbps are used to accomplish this, allowing for an additional 32-48 kbps of bit rate that can be used for video data.
T.120 - Standards that cover the document conferencing (data sharing) portion of a multimedia teleconference. The recommendations specify how to efficiently and reliably distribute files and graphical information in real-time during a multipoint multimedia meeting. The objective is to assure interoperability between terminals without either participant assuming prior knowledge of the other system; permit data sharing among participants in a multimedia teleconference, including whiteboard image sharing, graphic display information and image exchange; and, specify infrastructure protocols for audiographic or audiovisual applications.
T.121 - Generic Application Template: This provides a guide for development of T.120 application protocols.
T.122 - Multipoint Communication Service (MCS) Service Description: This describes the multi-port services available to developers.
T.123 - Protocol stacks for audio graphic and audiovisual teleconference applications: This specifies transport protocols for a range of networks.
T.124 - Generic Conference Control (GCC): This defines the application protocol supporting reservations and basic conference control services for multipoint teleconferences.
T.125 - Multipoint Communication Service (MCS) Protocol specification: This specifies the data transmission protocol for multipoint services.
T.126 - Multipoint still image and annotation protocol: This defines collaborative data sharing, including "whiteboard" image sharing, graphic display information, and image exchange in a multipoint conference.
T.127 - Multipoint Binary File Transfer Protocol: This defines a method for applications to transmit files in a multipoint conference.
T.130 - Realtime architecture for multimedia conferencing: Provides an overview description of how T.120 data conferencing works in conjunction with H.320 videoconferencing.
T.131 - Network-specific mappings: Defines how realtime audio and video streams should be transported across different networks (i.e. ISDN, LAN, ATM) when used in conjunction with T.120 data conferencing.
T.132 - Realtime link management: Defines how realtime audio and video streams may be created and routed between various multimedia conferencing endpoints.
T.133 - Audiovisual control services: Defines how to control the source and link devices associated with realtime information streams.
T.RES - Reservation Services: This is an overview document which specifies how terminals, MCUs, and reservation systems need to interact, and defines the interfaces between each of these elements.
T.Share - Application Sharing Protocol: This defines how participants in a T.120 conference can share local applications such that other conference participants can see the image of the shared application, and use the mouse and keyboard to take control of the shared application as if it were running locally.
T.TUD - User Reservation: This describes how to transport a user-defined bitstream between various endpoints in a T.120 data conference.
H.323 - Addresses videoconferencing over ISDN and other circuit switched networks and services. Since H.320 was ratified, in 1990, corporations have increasingly implemented Local Area Networks (LANs) and LAN gateways to the Wide Area Network (WAN). H.323 is a logical and necessary extension of the H.320 standard to include Corporate Intranets and packet-switched networks generally. Because it is based on the Real-Time Protocol (RTP/RTCP) from the IETF, H.323 can also be applied to video over the Internet.
H.225 - Specifies messages for call control including signaling, registration and admissions, and packetization/synchronization of media streams.
H.245 - Specifies messages for opening and closing channels for media streams, and other commands, requests and indications.
H.261 - Video CODEC for audiovisual services at P x 64 Kbps.
H.263 - Specifies a new video CODEC for video over POTS.
G.711 - Audio CODEC, 3.1 KHz at 48, 56, and 64 Kbps (normal telephony).
G.722 - Audio CODEC, 7 KHz at 48, 56, and 64 Kbps.
H.324 - Addresses and specifies a common method for sharing video, data and voice simultaneously using high-speed (V.34) modem connections over a single analog (POTS) telephone line. It also specifies interoperability under these conditions, so that videophones, for example, based on H.324 will be able to connect and conduct a multimedia session. Of the three ITU standards that address videoconferencing - H.324, H.323 and H.320 - H.324 has the broadest impact in the marketplace. That is because H.324 incorporates the most pervasive communications facility - POTS - installed today, on a global basis.
H.263 - Defines speech coding at rates less than 64 Kbps.
H.223 - Defines a Multiplexing protocol for low bitrate multimedia terminals.
H.245 - Defines control of communications between multimedia terminals.
G.723 - Defines speech coding for multimedia telecommunications transmitting at 5.3/6.3 Kbps.
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