H.323.


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... are the prevalent transport media utilized as a part of desktop feature conferencing. ... based multipoint sound and feature conferencing to existing desktop feature conferencing frameworks when utilized as a part of ...
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H.323 Liane Tarouco Leandro Bertholdo

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Standard elements Telecommunications principles are set by the United Nations office, International Telecommunications Union (ITU) The ITU has built up the H, G and T Series of measures Internet Engineering Task Force (IETF) characterizes stadards for the Internet IETF has grown Real-Time Protocol (RTP), Real-Time Control Protocol (RTCP) & Resource Reservation Protocol (RSVP). Items that stick to these gauges permit clients to take an interest in a meeting, paying little mind to their stage.

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Available Transport Media. ISDN, LAN, WAN, Internet, ADSL (Asynchronous Digital Subscriber Lines) and VPN, (Virtual Private Networks) are the famous transport media utilized as a part of desktop video conferencing. The overall accessibility of the Internet has essentially ceased the utilization of POTS (Plain Old Telephone Service) as an immediate method for interfacing video conferencing frameworks. Be that as it may, the inevitable media-empowered 3G cell telephone has brought about the making of a subsidiary of the H.324 POTS standard as 3G-324M and in addition cutting edge Gateways to transcode the new conventions.

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ISDN There are two accessible ISDN associations Basic Rate Interface (BRI) Primary Rate Interface (PRI). Basically, a BRI gives two 64kbps B-channels and one 16kbps D-divert while a PRI in Europe gives 30 x 64kbps B-channels and one 64kbps D-channel.

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ISDN associations typically total the BRI and offer the same number for both B channels. Known as ISDN-2, this gives a line velocity of 128kbps is normally utilized as a part of a desktop gathering over ISDN. For expanded data transfer capacity, ISDN-6 gives a line rate of 384kbps and is commonly utilized as a part of room-based meetings over ISDN. With ISDN-6, the succession in which the lines are collected must be known and followed as well! Besides, if the association is going to utilize some type of \'switch\', this must be designed to pass both voice and information!

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ISDN for multipoint gathering To hold a multipoint meeting over ISDN, members utilize a Multipoint Control Unit (MCU), that associates and deals with all the ISDN lines. This can be either a different MCU or an endpoint with an inserted H.320 multipoint capacity

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H.320 is the ITU standard for ISDN conferencing and incorporates: Audio: G.711, G.722, G.722.1, G.728 Video: H.264, H.263, H.261 Data: H.239, T.120 Control: H.221, H.231, H.242, H.243

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Local Area Network (LAN) or Intranet and Wide Area Network (WAN). LANs and WANs use TCP/IP convention and the H.323 standard characterizes how to collect the sound, video, information and control (AVDC) data into an IP bundle.

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DHCP Most organizations use DHCP and distribute dynamic IP locations to PC\'s. In this manner, keeping in mind the end goal to effectively distinguish a client, the H.323 endpoints are typically enrolled with a Gatekeeper and "called" into a meeting by their H.323 nom de plume. The Gatekeeper makes an interpretation of the nom de plume into the relating IP address. Another strategy for recognizing H.323 clients is for them to enlist their nearness utilizing Light Directory Access Protocol (LDAP) with a Directory Service, for example, Microsoft\'s Site Server ILS or Windows 2003 Active Directory.

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Multipoint gathering To hold a multipoint meeting over IP, H.323 frameworks require some type of Multipoint Conference Server (MCS). This is additionally alluded to as a H.323 Multipoint Control Unit (H.323 MCU), which is not the same as a H.320 MCU;

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Lan & WAN H.323 is the ITU standard for LAN conferencing and incorporates: Audio: G.711, G.722, G.722.1, G.723.1, G.728, G.729 Video: H.264, H.263, H.261 Data: H.239, T.120 Control: H.225, H.245

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Cellular Networks. The PDA system is a promptly accessible type of remote interactive media conveyance and with the anticipated media-empowered 3G cellular telephone or Personal Digital Assistants, PDAs, that backing the CDMA2000 or WCDMA Air Interface, there is adequate data transmission to empower IP-based multipoint sound and video conferencing to existing desktop video conferencing frameworks when utilized as a part of conjunction with cutting edge Gateways and MCU\'s that likewise bolster these new conventions.

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Cellular systems 3G-324M is an expansion by the third Generation Partner Project (3GPP) and third Generation Partner Project2 (3GPP2) to the ITU H.324M standard for 3G cell telephone conferencing and incorporates: Audio: G.722.2 (AMR-WB), G.723.1 Video: MPEG-4, yet not H.264 Control: H.223 A/B, H.245

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Internet, VPN & ADSL. Like LANs, the Internet, VPNs and ADSL are different types of TCP/IP systems and thus can be utilized as a vehicle media as a part of desktop conferencing frameworks. What the clients must do is to get their Internet Service Provider (ISP) to give them a settled IP address

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Directory benefits Alternatively, clients can enroll their nearness utilizing LDAP with a Directory Service, for example, Microsoft\'s Site Server ILS or Windows 2003 Active Directory. This is the manner by which you decide the location of the machine that you need to meeting with. Clearly, speed is constrained to that of the slowest connect, however most ISPs now bolster ISDN Dial-up at 128kbps or V.92 modems at 56kbps

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Internet H.323 is the ITU standard utilized for Internet conferencing and incorporates: Audio: G.723.1, G.722.1, G.728 Video: H.264, H.263, H.261 Data: H.239, T.120 Control: H.225, H.245

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Video models H.261 - video codec for varying media administrations at p x 64Kbps. H.263 - video codec for thin broadcast communications channels at < 64 Kbps. H.264/AVC - another video codec standard offering real upgrades picture quality.

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Image size QCIF is Quarter Common Intermediate Format and speaks to a 176x144 pixel picture. This is the base size that must be bolstered to be H.320 consistent. CIF is the discretionary full-screen H.320 video picture of 352x288 pixels and requires significantly additionally processing capacity. Note: while this is named full-screen, it is no place close to the extent of a commonplace PC screen (1024x768) pixels or that of a UNIX workstation (1280x1024) pixels.

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Video and PC Window Sizes NTSC - National Television Standards Committee, utilized as a part of USA, Canada & Japan. 640 x 480 pixels. Buddy - Phase Alternation by Line, utilized as a part of Europe (with the exception of France), Africa & Middle East. 768 x 576 pixels.

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Video and PC Window Sizes CIF - Common Intermediate Format; discretionary for both H.261 & H.263, 352 x 288 pixels. QCIF - Quarter Common Intermediate Format; required by both H.261 & H.263, 176 x 144 pixels. SQCIF - Sub Quarter Common Intermediate Format; utilized by 3G mobiles MPEG4 video and H.263, 88 x 72 pixels.

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Video and PC Window Sizes SXGA - 1280 x 1024 pixels - utilized by top of the line design workstations. XGA - 1024 x 768 pixels - run of the mill PC or portable PC determination. SVGA - 800 x 600 pixels. VGA - 640 x 480 pixels.

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H.264 Ratified in late 2003, this new codec standard was an advancement between the ITU and ISO/IEC Joint Video Team, (JVT) and is known as H.264 (ITU name) or ISO/IEC 14496-10/MPEG-4 AVC (ISO/IEC name). This new standard surpasses H.261 and H.263 as far as video quality, compelling pressure and flexibility to transmission misfortunes, giving it the possibility to split the required data transfer capacity for computerized video administrations over the Internet or 3G Wireless systems. H.264 is liable to be utilized as a part of uses, for example, Video Conferencing, Video Streaming, Mobile gadgets, Tele-Medicine and so forth. Current 3G mobiles utilize a derivate of MPEG-4, yet not H.264.

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Audio benchmarks G.711 - Pulse Code Modulation of voice frequencies (PCM), were 3.1 kHz simple sound is encoded into a 48, 56 or 64 kbps stream. Utilized when no other standard is similarly bolstered. G.722 - 7 kHz sound encoded into a 48, 56 or 64 kbps stream. Gives high caliber, yet takes data transmission. G.722.1 - 7 kHz sound encoded at 24 and 32 kbps for without hands operation in frameworks with low edge misfortune. G.722.2 - Coding of discourse at around 16 kbps utilizing Adaptive Multi-Rate Wideband, AMR-WB. Five required modes, 6.60, 8.85, 12.65, 15.85 and 23.85 kbps. G.723.1 - 3.4 kHz double rate discourse codec for media communications at 5.3 kbps & 6.4 kbps.

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Audio guidelines G.728 - 3.4 kHz Low Delay Code Excited Linear Prediction (LD-CELP) were 3.4 kHz simple sound is encoded into a 16 kbps stream. This standard gives great quality results at low bitrates. G.729 A/B - 3.4 kHz discourse codec that gives close toll quality sound encoded into a 8 kbps stream utilizing the AS-CELP strategy. Add A will be a decreased multifaceted nature codec and Annex B underpins hush concealment and solace commotion era.

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Data gauges T.120 - characterizes conventions and administrations for sight and sound conferencing. T.121 - Generic Application Template (GAT). Characterizes a format as an aide for engineers in overseeing T.120 assets. T.122 - characterizes Multipoint Communication Services (MCS) accessible to designers. T.123 - characterizes Network Specific Data convention for interactive media conferencing. T.124 - characterizes Generic Conference Control (GCC), obligatory for "gathering" meetings. T.125 - characterizes MCS information transmission convention.

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Data models T.126 - Multipoint Still Image and Annotation convention. Characterizes the convention used to furnish interoperability with design information in applications, for example, whiteboarding, commented on picture trade, screen sharing and remote applications control. T.127 - Multipoint Binary File Transfer convention. Characterizes the convention used to bolster twofold document exchange inside a meeting. T.128 - characterizes Multipoint Application Sharing convention (otherwise called T.SHARE) T.134 - characterizes Multimedia Application Text Conversation convention (otherwise called T.CHAT).

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Data principles T.135 - User-to-reservation framework exchanges inside T.120 conferencing. T.136 - Remote gadget control application convention. T.137 - Virtual meeting room administration

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