- Recommendation H.223 (07/01) – Multiplexing Protocol for Low Bit Rate Multimedia Communication
This Recommendation specifies the frame structure, format of fields and procedures of the packet multiplexing protocol for low bit rate multimedia communication. This protocol can be used between two low bit rate multimedia terminals, or between a low bit rate multimedia terminal and a Multipoint Control Unit (MCU) or an InterWorking adapter (IWA).
The protocol allows the transfer of any combination of digital voice/audio, digital video/image and data information over a single communication link. This protocol provides low delay and low overhead by using segmentation and reassembly and by combining information from different logical channels in a single packet. The control procedures necessary to implement this multiplexing protocol are specified in Recommendation H.245.
In this Recommendation communication between different protocol layers is modeled as a set of abstract primitives, which represent a logical exchange of information. The decomposition of functionality into (sub)layers, as well as the description of the primitives, do not imply a particular method of implementation. In particular, layers may exchange the contents of a logical unit (an SDU) in a "streaming" mode where information exchange may start before the transferring layer has the complete unit in its possession.
- Recommendation H.225.0 (12/09) - Call signalling protocols and media stream packetization for packet-based multimedia communication systems.
This Recommendation covers the technical requirements for narrow-band visual telephone services defined in H.200 and F.720-series Recommendations, in those situations where the transmission path includes one or more packet-based networks, each of which is configured and managed to provide a non-guaranteed Quality of Service (QoS) which is not equivalent to that of N-ISDN, such that additional protection or recovery mechanisms beyond those mandated by ITU-T Rec. H.320 need be provided in the terminals. It is noted that ITU-T Rec. H.322 addresses the use of some other LANs which are able to provide the underlying performance not assumed by the ITU-T Recs H.323 and H.225.0.
This Recommendation describes how audio, video, data, and control information on a packet-based network can be managed to provide conversational services in H.323 equipment.
Products claiming compliance with Version 7 of H.225.0 (this version) shall comply with all of the mandatory requirements of this Recommendation. Version 7 products can be identified by H.225.0 messages containing a protocolIdentifier value of {itu-t (0) recommendation (0) h (8) 2250 version (0) 7}.
- Recommendation H.246 (05/06) – Interworking of H-series multimedia terminals with H-series multimedia terminals and voice/voiceband terminals on GSTN and ISDN
This revision of H.246 incorporates the separately published text of Amendment 1 (Usage of H.243 multipoint control messages and support for Unicode characters in H.320 systems), Annex E1 (Mobile Application Part and H.225.0 interworking), Annex E2 (ANSI-41 (Americas) Mobile Application Part and H.225.0 interworking), Annex C (Annex C:ISDN User Part function - H.225.0 interworking, and Annex F (H.323-H.324 interworking), along with some changes of editorial nature. It also incorporates the technical and editorial corrections from the H.323 System Implementors’ Guide (09/2005).
- Recommendation H.263 (01/05) - Video coding for low bit rate communication
This Recommendation specifies a coded representation that can be used for compressing the moving picture component of audio-visual 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 video source formats: sub-QCIF, QCIF, CIF, 4CIF and 16CIF, and can also operate using a broad range of custom video formats.
The decoder has motion compensation capability, allowing optional incorporation of this technique in the coder. Half pixel precision 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.
In addition to the basic video source coding algorithm, eighteen negotiable coding options are included for improved compression performance and the support of additional capabilities. Additional supplemental information may also be included in the bitstream for enhanced display capability and for external usage.
- Recommendation H.264 (03/05) - Advanced video coding for generic audiovisual services
As the costs for both processing power and memory have reduced, network support for coded video data has diversified, and advances in video coding technology have progressed, the need has arisen for an industry standard for compressed video representation with substantially increased coding efficiency and enhanced robustness to network environments.
This Recommendation | International Standard was developed in response to the growing need for higher compression of moving pictures for various applications such as videoconferencing, digital storage media, television broadcasting, internet streaming, and communication. It is also designed to enable the use of the coded video representation in a flexible manner for a wide variety of network environments. The use of this Recommendation | International Standard allows motion video to be manipulated as a form of computer data and to be stored on various storage media, transmitted and received over existing and future networks and distributed on existing and future broadcasting channels.
- Recommendation H.323 (06/06)- Packet-based multimedia communications systems
This Recommendation covers the technical requirements for multimedia communications systems in those situations where the underlying transport is a Packet Based Network (PBN) which may not provide a guaranteed Quality of Service (QOS). These packet based networks may include Local Area Networks, Enterprise Area Networks, Metropolitan Area Networks, Intra-Networks, and Inter-Networks (including the Internet). They also include dial up connections or point-to-point connections over the GSTN or ISDN which use an underlying packet based transport such as PPP. These networks may consist of a single network segment, or they may have complex topologies which incorporate many network segments interconnected by other communications links.
This Recommendation describes the components of an H.323 system. This includes Terminals, Gateways, Gatekeepers, Multipoint Controllers, Multipoint Processors, and Multipoint Control Units. Control messages and procedures within this Recommendation define how these components communicate.
This Recommendation describes terminals and other entities that provide multimedia communications services over Packet Based Networks (PBN) which may not provide a guaranteed Quality of Service. H.323 entities may provide real-time audio, video and/or data communications. Support for audio is mandatory, while data and video are optional, but if supported, the ability to use a specified common mode of operation is required, so that all terminals supporting that media type can interwork.
The packet based network over which H.323 entities communicate may be a point-to-point connection, a single network segment, or an internetwork having multiple segments with complex topologies.
H.323 entities may be used in point-to-point, multipoint, or broadcast (as described in ITU-T Rec. H.332) configurations. They may interwork with H.310 terminals on B-ISDN, H.320 terminals on N-ISDN, H.321 terminals on B-ISDN, H.322 terminals on Guaranteed Quality of Service LANs, H.324 terminals on GSTN and wireless networks, V.70 terminals on GSTN, and voice terminals on GSTN or ISDN through the use of Gateways.
- Recommendation H.324 (04/09) - Terminal for low bit-rate multimedia communication.
This Recommendation describes terminals for low bit-rate multimedia communication, utilizing V.34 modems operating over the GSTN, I.400-series user-network interface for ISDN or an appropriate wireless interface for mobile networks. H.324 terminals may carry real-time voice, data, and video, or any combination, including videotelephony.H.324 terminals may be integrated into personal computers or implemented in stand-alone devices such as videotelephones. Support for each media type (voice, data, video) is optional, but if supported, the ability to use a specified common mode of operation is required, so that all terminals supporting that media type can interwork. This Recommendation allows more than one channel of each type to be in use. Other ITU-T Recommendations in the H.324-Series include the H.223 multiplex, H.245 control, H.263 video codec, and G.723.1 audio codec.
This Recommendation makes use of the logical channel signalling procedures of ITU-T Rec. H.245, in which the content of each logical channel is described when the channel is opened. Procedures are provided for expression of receiver and transmitter capabilities, so transmissions are limited to what receivers can decode, and so that receivers may request a particular desired mode from transmitters. Since the procedures of this Recommendation are also planned for use by ITU-T Rec. H.310 for ATM networks, and ITU-T Rec. H.323 for non-guaranteed bandwidth LANs, interworking with these systems should be straightforward.H.324 terminals may be used in multipoint configurations through MCUs, and may interwork with H.320 terminals on the ISDN, as well as with terminals on wireless networks.
- Recommendation H.501 (03/02) - Protocol for mobility management and intra/inter-domain communication in multimedia systems
The purpose of this Recommendation is to define messages and procedures for mobility management and for communication within and between domains of a mobile or non-mobile multimedia environment for the purpose of address resolution, user authentication, service data exchange, access authorization, call validation and usage reporting.
This Recommendation describes a protocol for communication between logical elements of a multimedia packet network to allow the completion of calls to and from users managed by such logical elements. This protocol can be used in mobile and non-mobile environments for the purpose of address resolution, user authentication, service data exchange, access authorization, call validation and usage reporting. These capabilities enable the protocol to be used for mobility management in mobile environments.
The general procedure is for logical elements to exchange information regarding the location of users or endpoints, in the form of addresses each administrative domain can resolve. Addresses can be specified in a general manner or in an increasingly specific manner. Additional information allows elements within an administrative domain to determine the most appropriate administrative domain to serve as the destination for the call. Logical elements may control access to their exposed addresses, and require reports on the usage made during calls to those addresses.
- Recommendation H.510 (03/02) - Mobility for H.323 multimedia systems and services
The purpose of this Recommendation is to define services and procedures for the support of mobility in H.323 multimedia systems.
This Recommendation deals with mobility aspects for H.323 systems above the transport layer. H.510 applies new functions defined in support of mobility management to H.323-compliant systems.
The main focus is on the support of terminal mobility, although support of user mobility in the context of H.323 is covered as well. This version of this Recommendation does not cover handover procedures where active calls can be maintained during location changes.
Interworking with other networks to support mobility across networks of different types is outside the scope of this Recommendation.
- Recommendation H.530 (03/02) - Symmetric security procedures for H.323 mobility in H.510
The purpose of this Recommendation is to describe security procedures for an H.323 multimedia mobility environment. This Recommendation provides the details about the security procedures for H.510.
So far, the signalling capabilities of ITU-T Rec. H.235 in its versions 1 and 2 [4] are designed to handle security in mostly static H.323 [5] environments. Those environments and multimedia systems can achieve some limited mobility within gatekeeper zones; ITU-T Rec. H.323 [5] in general and ITU-T Rec. H.235 [4] specifically provide only very little support for secure roaming of mobile users and terminals across different domains with many involved entities in a mobility, distributed environment for example.
The H.323 mobility scenarios depicted in ITU-T Rec. H.510 [6] regarding terminal mobility pose a new situation with their flexible and dynamic character also from a security point of view. Roaming H.323 users and mobile terminals have to be authenticated by a foreign, visited domain. Likewise, the mobile user would like to obtain evidence about the true identity of the visited domain. In addition to that, it may be also useful to obtain evidence about the identity of the terminals complementing user authentication. Thus, these requirements demand for mutual authentication of the user and the visited domain and optionally also of the identity of the terminal.
As the mobile user is usually known only to the home domain where the user is subscribed and assigned a password, the visited domain initially does not know the mobile user. As such, the visited domain does not share any established security relationship with the mobile user and the mobile terminal. In order to let the visited domain achieve the authentication and authorization assurance for the mobile user and for the mobile terminal, the visited domain would relay certain security tasks such as authorization checks or key management to the home domain through intermediate network and service entities. This requires securing the communication and key management between the visited domain and the home domain too.
While, in principle, mobility H.323 environments are more open than closed H.323 networks, there is of course also need to appropriately secure the key management tasks. It is also true that communication within and across the mobility domains deserves protection against malicious tampering.
In summary, this Recommendation describes a generic security concept for mobility among domains for multimedia applications and multimedia services. The technical details describe the deployment for H.323 and for H.510 in particular, but are considered potentially open to other environments.
- Recommendation G.722.2 (07/03) – Wideband coding of speech at around 16 kbit/s using adaptive multi-rate Wideband (AMR-WB)
This Recommendation describes the high quality Adaptive Multi-Rate Wideband (AMR-WB) encoder and decoder that is primarily intended for 7 kHz bandwidth speech signals. AMR-WB operates at a multitude of bit rates ranging from 6.6 kbit/s to 23.85 kbit/s. The bit rate may be changed at any 20 ms frame boundary.
G.722.2 AMR-WB is the same codec as the 3GPP AMR-WB. The corresponding 3GPP specifications are TS.26.190 for the speech codec and TS 26.194 for the Voice Activity Detector.
- G.728 (1992) Amendment 1 (05/06) - revised Annex J - Variable bit rate operation of LD-CELP mainly for voiceband-data applications in DCME
Annex J to ITU-T Rec. G.728 defines a 40 kbit/s extension optimized for voiceband data signals of the existing Annex G/G.728 - 16 kbit/s fixed point specification. The main difference between the codec described hereby and the codec described in Annex G/G.728 is the application of a Trellis-Coded Quantization (TCQ) approach to codebook search. The TCQ approach replaces the analysis-by-synthesis approach to codebook search of ITU-T Rec. G.728 only in voiceband data (VBD) mode.
The backward adaptation of the predictor achieved in VBD mode is almost identical to the backward adaptation achieved in speech mode (ITU-T Rec. G.728). Additionally, the same adaptation cycle is used for both speech mode (ITU-T Rec. G.728) and VBD mode. In speech mode, the 40 kbit/s reverts to the LD-CELP of ITU-T Rec. G.728.
This annex includes an electronic attachment containing test vectors for implementation verification of Annex J/G.728.
- Recommendation G.729 (01/07) - Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear prediction (CS-ACELP).
This Recommendation contains the description of an algorithm for the coding of speech signals at 8 kbit/s using Conjugate-Structure Algebraic-Code-Excited Linear-Prediction (CS-ACELP).
This coder is designed to operate with a digital signal obtained by first performing telephone bandwidth filtering (Recommendation G.712) of the analogue input signal, then sampling it at 8000 Hz, followed by conversion to 16-bit linear PCM for the input to the encoder. The output of the decoder should be converted back to an analogue signal by similar means.
- Recommendation G.729.1 (05/06) – G.729 based Embedded Variable bit-rate coder: An 8-32 kbit/s scalable wideband coder bitstream interoperable with G.729
G.729.1 describes an 8-32 kbit/s scalable wideband (50-7000Hz) audio/speech coding algorithm extension to the ITU-T G.729 speech coder/ G.729.1 can encode wideband signals at bitrates of 14 to 32 kbit/s. The produced embedded bitstream has granularity steps of 2 kbit/s allowing graceful quality improvements. G.729.1 can also be used as a narrowband codec to encode 50-4000 Hz signals at bit rates of 8 and 12 kbit/s. At 8 kbit/s, the bitstream is compliant with the G.729 bitstream format. This allows full interoperability with G.729, G.729 Annex A and G.729 Annex B. Hence an efficient deployment in existing G.729 based VoIP infrastructures is foreseen. Frame size (20 ms), delay (48.9375 ms), complexity (35.8 WMOPS) and quality in various conditions are all compliant with the requirements set and suitable for the targeted applications.
