H.320 MULTIMEDIA CONFERENCING STANDAR

Multimedia communication 24-Mar-15

PREPARED BY:ANILA SAGHIR TC-17

FARHEEN NAJEEB TC-43YUSRA KANWAL TC-46

IQRA AYUB TC-51

H.320 MULTIMEDIA CONFERENCING STANDARD

YUSRA KANWALTC-046

INTRODUCTION

H.320 Multimedia Conferencing Standards 2

• Multimedia conferencing, or video conferencing, is an important application of real time media

• Multimedia conferencing refers to meetings at a distance that involve some combination of audio, video, and data collaboration

• When these meetings contain all three media types they are called videoconferences

Introduction

• As an advanced communication tool, inter-connectivity and inter-operability require

* that the video conferencing devices involved in the same conference can talk to each other

* i.e., they comply with some common standard

Introduction(cont..)

• Multimedia conferencing standard is an umbrella set of standards because

* specifies audio and video coding standards

* addresses call control, conference management, media packet formation and delivery

Multimedia Conferencing Standard

• There are two major categories of Multimedia conferencing standards:

* H.32x series from the telecommunication world, standardized by ITU (International Telecommunications Union)

* SIP (Session Initial Protocol) based video conferencing standard from the Internet World, Recommended By IETF (Internet Engineering Task Force)

Multimedia Conferencing Standard(cont..)

• All of today’s ITU-T standard-based multimedia conferencing protocols are built from a similar base architecture

• Each standard shares the same basic components that are organized to deliver control, audio, video, and data collaboration to the user

• The differences between the standards are driven from each standards optimal packaging of data for transmission on the network for which they were designed to service

Multimedia Conferencing Architecture

• Multimedia conferencing equipment can be categorized into terminals or end-user devices

• Figure 1 shows the generic multimedia terminal architecture’s basic components:

Multimedia Conferencing Architecture(cont…)

• H.320, the first international standard of video conferencing, was released by ITU in the early 1990s

* The standard was designed for narrow band switched ISDN (Integrated Service Digital Networks)

• Later on its variants for different network infrastructures were standardized in the mid and late 1990s

ITU-T H.32x Multimedia Conferencing Standards

• Its different variants include

* H.321 3 (for broadband ISDN)

* H.322 4 (for guaranteed bandwidth packet switched networks)

* H.324 6 (for Public Switched Telephone Network)

* H.323 5 (for non-guaranteed bandwidth packet switched networks)

ITU-T H.32x Multimedia Conferencing Standards

• The ISDN based multimedia conferencing market has been deployed using the ITU-T’s H.320 conferencing standard

• H.320 became a standard in 1990 and is used as the default mode of operation by every major manufacturer of ISDN based videoconferencing equipment

• The protocol is built on a bit level multiplex that can use multiple ISDN B-channels 64 Kbps to send control, audio, video, and data information

H.320 Multimedia Conferencing Standard

• The multiplex, which formats data in a synchronous stream where fields are distinguished by bit position, does not require packet headers

• The lack of packet headers makes the multiplex very efficient in its use of bandwidth but requires

* complex implementation

* significant amount of processing power to operate in real-time

H.320 Multimedia Conferencing Standard(cont..)

ANILA SAGHIRTC-017

H.320 Components

• H.320 consists of

* Terminals

* and multipoint control units called MCUs

• The terminal is the end-user device that is used to participate in a point-to-point or multipoint conference

• A MCU is a network device that enables a terminal to participate in a multipoint conference

H.320 Components

• Fig. 2 shows the relationship of the terminal and the MCU for H.320

H.320 Components (cont..)

• Audio codec

• Video codec

• Synchronization

• Data application

• Data services

• Multiplexer/de-multiplexer

• System control

• Call setup/signaling

H.320 Terminal

A H.320 terminal includes the following components:

• Call setup/signaling

* H.320 uses the ISDN call signaling protocol Q.931 for call setup and tear down

• Connection control :

* Connection control is carried out by the H.242 and H.243 protocols

• Audio codec:

* Although H.320 specifies G.711 as its base audio codec, but G.722 and G.728 are also used

H.320 Terminal(cont..)

• Video codec:

* H.320 specifies the H.261 video codec as mandatory and the H.263 video codec as optional

• Data applications:

* Standard data applications defined for use with H.320 come from the T.120 protocol suite. These applications include

� T.126 for still image exchange and white boarding

� T.127 for file transfer

� T.128 for application sharing

• Data services:

* Data services in H.320 are provided by the T.120 protocol suite. The data services include

� generic conference control GCC (T.124)

� and multipoint communication service MCC (T.122)

• Synchronization(Transmit Audio Delay):

* In H.320, the addition of audio delay for synchronization is optional

• Multiplex:

* H.221 provides the H.320 multiplex capability

• To conduct a multipoint conference, a MCU performs

* the capability negotiations between its attached endpoints

* to achieve a common operating mode and controls

• MCU functionality can be broken into three main Components

* control processing

* media processing

* media distribution

H.320 Multipoint Control Unit(MCU)

• Control processing:

* A MCU is responsible for the connection control processing associated with each terminal connection in a conference

• Media processing:

* A MCU processes the audio, video, and data received from each terminal in a conference based on the configuration defined for that conference

• Media distribution:

* MCU distributes individual audio, video, data, and control streams to each terminal in a conference

H.320 Multipoint Control Unit(cont..)

• The audio codec carries out redundancy reduction coding and decoding for audio signals

• Audio codec is a technique implementing an algorithm

* that compresses and decompresses digital audio data according to a given audio file format or streaming media audio format

Audio Codec

• The object of the algorithm is

* to represent the high-fidelity audio signal with minimum number of bits

* while retaining the quality

• This can effectively reduce

* the storage space and

* the bandwidth required for transmission of the stored audio file

Audio Codec(cont..)

• Although H.320 specifies G.711 as its base audio codec

• But

* Most 128 Kbps conferences Basic Rate ISDN use G.728 for their audio mode

* And most 384 Kbps Primary Rate ISDN Conferences use G.722

Audio codecs for H.320

• Table shows the details of the audio algorithms specified for use in H.320

Audio codecs for H.320(cont..)

Algorithm Audio bandwidth Type of algorithm Bit rate

Frame duration

or sample rate

G.711 Narrowband _3

PCM _Pulse Code

Modulation

48, 56, or

8 kHz sample

G.722 Wideband

Sub band ADPCM

_Adaptive Differential

48, 56, or

8 kHz sample

G.728 Narrowband

LD-CELP _Low Delay

Code Excited Linear

Prediction

16 2.5 ms frame

• G.711 is the international standard for encoding telephone audio on an 64 kbps channel

* Its formal name is Pulse code modulation (PCM) of voice frequencies

• Sampling rate:

* G.711 uses a sampling rate of 8,000 samples per second, with the tolerance on that rate 50 parts per million (ppm)

* Non-uniform (logarithmic) quantization with 8 bits is used to represent each sample, resulting in a 64 kbps bit rate

• Audio bandwidth: G.711 can encode frequencies between 0 and 4 kHz

• Encoding law: Telco’s can select between two different variants of G.711 and these are commonly referred to as the * A-law* µ-law

• A-law is the standard for international circuits

• Each of these encoding schemes is designed in a roughly logarithmic fashion

• Lower signal values are encoded using more bits

G.711(cont..)

• higher signal values require fewer bits

• This ensures that low amplitude signals will be well represented, while maintaining enough range to encode high amplitudes

• Transmission of character signals: When character signals are transmitted serially, i.e. consecutively on one physical medium

* bit No. 1 (polarity bit) is transmitted first

* And No. 8 (the least significant bit) last

G.711(cont..)

• When network traffic is normal, a low-compression algorithm is used but

* When network traffic is heavy, bandwidth is automatically conserved by means of a higher than usual ratio of digital compression

• The G.722 ITU Standard is a wideband audio codec

• It is a standard for high-quality digital voice communications

• It operates at a data sampling rate of 16kbps

* which is double that of a traditional Pulse Code Modulated telephone

• The higher sampling rate allows the G.722 codec to provide higher clarity of audio signals than G.711

• The G.722 codec can provide 7 kHz wideband speech at transmission rates of 48Kbps, 56Kbps and 64Kbps

G.722(Cont..)

• A key reason the G.722 codec is used by broadcasters to transmit speech via telephone lines [ISDN 64Kbps B Channels can carry G.722]

* is the greater level of audio clarity it provides

* In practice, this codec generally negotiates at 64Kbps even though it can operate at lower bandwidth rates

G.722(cont..)

• G.728 is an ITU-T standard for audio coding

* And specified as part of the H.320 international video conferencing standard

* operating at 16 kbps

* uses low-delay code excited linear prediction(LD-CELP)

• G.728 coders are widely used for applications of

* telephony over packet networks

* especially voice over cable and VoIP, where low delay is required

• Video codec requires processing delays

• So to maintain lip synchronization

* audio must be delayed in the system

• In H.320, Transmit Audio Delay enable the audio is to be delayed in the transmitter

* to compensate for the video encode path delay

* to allow the receiver to maintain lip synchronization

Synchronization(Transmit Audio Delay)

FARHEEN NAJEEB TC-043

SYSTEM CONTROL,CALL SETUP & MULTIPLEXING IN

Call Setup

• The call setup procedure associated with an ISDN is defined in recommendation Q.931

ITU standard ISDN connection

control signaling protocol

• The system control unit carries out such functions as network access through end-to-network signaling and end-to-end control

• The system control standard :

* H.242

* H.230

SYSTEM CONTROL

• ITU-T Recommendation for a system for establishing communications between audiovisual terminals

• H.242 addresses :

* call setup and teardown

* in-band signaling and control

* channel management

• Frame synchronous control and indication signals for audiovisual systems

• Defines call control

• Defines the transmission frame structure for audiovisual tele-services in channels of 64 to 1920 Kbps

MULTIPLEXING

• Divide bit stream into 80 octet frames

• Logically, divide each frame into 8 sub channels

• Bit 1 of each octet is in sub channel 1, etc.

H.221 FRAMING

• Sub channel 8 contains metadata (and some real data):

• FAS(Frame Alignment Signal):

* Easily recognized bit pattern repeated in alternate frames

• BAS(Bandwidth Allocation Signal):

* Sequence of code points used to negotiate how the sub channels are used and to add sub channels for higher data rates

H.221 FRAMING(cont..)

• There are many different ways of dividing up the sub channels between audio, video and data

H.221 FRAMING(cont..)

IQRA AYUBTC-051

USER DATA APPLICATIONS

• The user data applications are based on the T.120

standard which, in practice, consists of a set of

recommendations

• There is a set of application-specific

recommendations that support the sharing of

various media types

• These all recommendations are ITU-T

recommendations

User Data Applications

• The T.120 standard contains: A series of

communication and application protocols and

services

• T.120 Recommendations s series: Provides support for

real-time, multipoint data communications for use in

multimedia conferencing environment

User Data Applications(cont..)

• T.120 Recommandation series contains following

components:

* T.121 (1996)

* T.122 (1993)

* T.123 (1993)

* T.124 (1995)

* T.125 (1994)

* T.126 (1995)

* T.127 (1995)

T.120 Components

Model of T.120 Series Architecture

• Transport Protocols - T.123:

* Specifies transport profiles for

PSTN,ISDN,CSDN,PSDN and TCP/IP

* Protocol Stack for Audio graphics and

Audiovisual Teleconference Application

* Includes built-in error correction facilities

Components Overview

• Multipoint Communication Service (MCS) - T.122,

* T.122: Defines multipoint services available to

the developer

* T.125: Specifies data transmission Protocol

Components Overview(cont..)

• T.124 : Generic Conference Control (GCC)

* Provides set of facilities for establishing

and managing the multipoint conference

* Provides conference security

Components Overview(cont..)

• T.121: Generic Application Template (GAT)

• T.126 : Multipoint Still Image and Annotation

Protocol (MSIA)

• T.127 : Multipoint Binary File Transfer Protocol

(MBFT)

Components Overview (cont..)

• Node Controller

* The Node Controller manages defined GCC Service Access Points (SAPs)

* This provides the node flexibility in responding to GCC events

* Most of these GCC events relate to:

� establishing conferences

� adding or removing nodes from a conference

� breaking down and distributing information

Components Overview (cont..)

• Multipoint Data Delivery

• Interoperability

• Reliable Data Delivery

• Multicast Enabled Delivery

• Network Transparency

• Application Independence

• Co-existence with Other Standards

• Extendibility

• Support for Varied Topologies

Key Benefits of T.120

• Video Conferencing Standards by TANDBERG, Application Notes,D10740, Rev 2.3

• Computer Networks 31 1999. 225–235(Multimedia conferencing over ISDN and IP networks using ITU-T H-series recommendations: architecture, control and coordination Mark )

• Reid VideoSerÍer Inc., 63 Third AÍenue, Burlington, MA 01803, USA

• http://www.itu.int/rec/T-REC-G.711/e

• http://www.freesoft.org/CIE/Topics/127.htm

• http://www.allaboutfoip.com/g711.html

• ITU-T Recommendation T.120(1996), Data Protocol for Multimedia Conference.

• A Primer on the T.120 Series Standard, http://www.packetizer.com/ipmc/t120/primer/

References

THANK YOU

H.320 MULTIMEDIA CONFERENCING STANDAR

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