IPTV Luan Van

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    I HC QUC GIA H NI

    TR NG I HC CNG NGH

    ===Fotech===

    Ng c C ng

    CC GII PHP CNG NGHV TRUYN TNHIU TRUYN HNH TRN MNG

    KHO LUN TT NGHIP I HC HCHNH QUY

    Ngnh :in t - Vin thng

    H NI 2005

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    I HC QUC GIA H NITR NG I HC CNG NGH

    ===Fotech===

    Ng c C ng

    CC GII PHP CNG NGHV TRUYN TNHIU TRUYN HNH TRN MNG

    KHO LUN TT NGHIP I HC HCHNH QUY

    Ngnh :in t - Vin thng

    Cn bh ng dn : TS. Ng Thi Tr Cn b ng h ng dn : KS. Bi Vn Thnh

    H NI 2005

    Ngc C ng L p K46B - Tr ng H Cng Ngh 2

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    L I CM N

    Sau mt th i gian nghin cu v thc t p ti Trung tm Tin hc vo l ng i truyn hnh Vit Nam, v i sgip n tnh ca cc cn b thuc Trung tmgip em hon thnh Kho lun tt nghi p.

    Qua y em xin trn tr ng gi l i cm n n Thy gio TS Ng Thi Tr -

    ng i tn tm h ng dn, ch bo v ng vin em trong sut qu trnh thc t pcng nhkhi bt u nghin cu v hon thnhti.

    Xin c gi l i cm n chn thnhn KS Bi Vn Thnh (cn bTrungtm Tin hc vo l ng i truyn hnh Vit Nam) vsh ng dn, ch bo nhittnh trong sut qu trnh thc t p v hon tt kho lun.

    Cui cng, em v cng bit n sgip v to mi iu kin thun l i nhtca gia nh, bn b v thy c gio - nhng ng i gip , ng vin em trong

    sut nhng nm hc qua. M t l n n a xin chn thnh c m n !

    H N i, thng 6 n m 2005Sinh vin

    Ng c C ng

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    TM TT NI DUNG

    Truyn tn hiu truyn hnh trn mng l mt vn l n t ra cho chai ngnhTruyn hnh v Internet. Mt cu hi t ra y l lm thno truyn c tnhiu truyn hnh (cvideo v audio) v i dung l ng l n trn ng truyn Internet bng thng h p hin nay v bi ton y chnh l vn bng thng. Tr i qua th igian di chng ta m i tm c l i gii cho bi ton ny chnh l nhng k t qut nhng thnh tu m i trong l nh vc truyn dn Internet tc cao -c bit l cngngh ng dy thu bao bt i xng ADSL (Asymmetric Digital Subscriber Line)s dng k thut truyn dn bng r ng cho php nng tc ti (download) ln 2Mbps, 5 Mbps v cao h n na. Bn cnh l k thut nnnh ng v i cc chunnn MPEG-2, MPEG-3, MPEG-4, MPEG-7, MPEG-21( chun MPEG-4 cho phpgim tc truyn ti cn thit ca truyn hnh s t 4 6 Mbps xung cn 1,5 2Mbps). Tuy nhin, hin nay l i gii ny c thl ti u nht nhng v i spht trinnhv bo ca khoa hc cng nghth chng ta stm c nhng gii php c tnhu vit h n na.

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    THUT NG

    A/D

    ADSL

    ARP

    ASF

    CD

    CPED/A

    DNS

    DRM

    DSM

    DVB

    DVDFTP

    HDSL

    HTML

    HTTP

    ICMP

    IETFIP

    IPA

    IPv4

    IPv6

    ISDN

    Analog to Digital Converter

    Asymmetric Digital Subscriber Line

    Address Resolution Protocol

    Advanced Streaming Format

    Compact Disk

    Customer Premise EquipmentDigital to Analog Converter

    Domain Name Server

    Digital Rights Management

    Digital Storage Media

    Digital Video Broadcasting

    Double Video Disk File Tranfer Protocol

    High bit rate Digital Subscriber Line

    HyperText Markup Language

    HyperText Transfer Protocol

    Internet Control Message Protocol

    Internet Enginerring Task ForceInternet Protocol

    Interactive Production Area

    Internet Protocol version 4

    Internet Protocol version 6

    Intergrated Services Digital Network

    Bchuyn i t ng tsang s

    ng dy thu bao sbt i xng

    Giao thc phn gii a ch

    nh dng dng tin tin

    a quang

    Thit b tr gip khch hngBchuyn i ssang t ng t

    Dch vtn min

    Qun l bn quyn dliu s

    Thit b lu tr dliu s

    Pht sng video squng b

    a video dung l ng l nGiao thc truyn t p tin

    ng dy thu bao stc cao

    Ngn ng nh du siu vn bn

    Giao thc truyn siu vn bn

    Giao thc nhm tiniu khin mng

    Tchc tiu chun mng quc t Giao thc mng Internet

    Khu vc sn xut ch ng trnh t ng tc

    Giao thc mng phin bn 4

    Giao thc mng phin bn 6

    Mng stch h p a dch v

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    ISP

    LDAP

    MAC

    MPEG

    MRG

    MSA

    NAT

    NTSC

    PAL

    PDA

    QOS

    RMP

    RSVP

    RTCP

    RTP

    RTSP

    SMIL

    SSL

    STBS-VCD

    TCP

    TLS

    VCD

    VHS

    VOD

    Internet Services Provider

    Lightweight Directory Access Protocol

    Media Access Control

    Moving Picture Experts Group

    Multimedia Research Group

    MultiStreaming Area

    Information content NATural unit

    National Television System Commitee

    Phase Alternating Line

    Personal Digital Assistant

    Quality of Service

    Reliable Multicast Protocol

    Resource Reservatiion Protocol

    Real-time Control Protocol

    Real-time Transport Protocol

    Real-time Streaming Protocol

    Syschronized Multimedia Integration

    Language

    Secure Socket Layer

    Set Top BoxSuper Video Compact Disk

    Transport Control Protocol

    Transport Layer Security

    Video Compact Disk

    Video Home System

    Video on Demand

    Nh cung c p dch vInternet

    Chun gin dch v

    iu khin truy c p thit b

    Tchc chuyn nghin cunh ng

    Tchc nghin cu dch v a ph ng tin

    Khu vc dch v a lung

    n v tnhin cha thng tin

    Uban vhthng truyn hnh quc t

    Pha thayi theo tng dng

    Thit b htr c nhn

    Dch vtin cy

    Giao thc truyn a dng tin cy cao

    Giao thc dnh ring ti nguyn mng

    Giao thc kim sot th i gian thc

    Giao thc truyn ti th i gian thc

    Giao thc dng dliu th i gian thc

    Ngn ngtch h p truyn thnga ph ng

    tin ng b

    L p bo vkhe h trong mng

    H p chuyn i tn hiu ssang t ng t a hnh c dung l ng l n

    Giao thc iu khin truyn tin

    Bo mt l p truyn tin

    a quang c hnh

    Hthng truyn hnh ti nh

    Truyn hnh theo yu cu

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    VPN

    XML

    Virture Private Network

    Extansible Markup Language

    Mng ringo

    Ngn ng nh du m r ng

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    MC LC--------&&--------

    L I GI I THIUCH NG 1 : TNG QUAN V TRUYN HNH INTERNET

    1.1 Gi i thiu

    1.3 S hi tcc u im ca truyn hnh sv Internet

    1.4 Khi nim truyn hnh Internet

    1.5 Nh ng ng dng ca truyn hnh Internet

    CH NG 2 : KHI QUT VCNG NGH TRUYN HNH INTERNET

    2.1 Gi i thiu vmng truyn hnh Internet

    2.1.1 Cu trc mng

    2.1.2 Cc chun mng

    2.1.3 Khnng nng c p mng

    2.1.4 Trin khai l p t mng

    2.1.5 Chi ph

    2.2 Cng nghtruyn hnh Internet

    2.2.1 To ch ng trnh truyn hnh

    2.2.1.1 Truyn hnh theo yu cu

    2.2.1.2 Truyn hnh tr c ti p trn mng

    2.2.2 Truyn dn v phn phi

    2.2.3 Hin th

    CH NG 3 : CC CNG NGH TRUYN THNGA PH NG TIN

    TRN MNG HIN NAY

    3.1 Khi qut vmng Internet v m hnh TCP/IP

    3.1.1 Mng Internet

    3.1.1.1 Gi i thiu vInternet

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    3.1.1.2 Ccng dng ca Internet

    3.1.2 M hnh TCP/IP

    3.1.2.1 Giao thc mng IP3.1.2.2 Giao thc TCP

    3.1.3 Gi i thiu cng nghADSL

    3.2 Cc ph ng php truyn thng a ph ng tin

    3.2.1 IP Unicast

    3.2.2 IP Multicast

    3.2.2.1 Truyn thng IP Multicast trn mng Internet3.2.2.2nh tuyn trong truyn thng IP Multicast

    3.2.3 Truyn thng IP Simulcast

    3.2.3.1 Nguyn l truyn thng IP Simulcast

    3.2.3.2 Ph ng thc hot ng truyn thng IP Simulcast

    3.2.3.3m bo cht l ng dch vsdng truyn dn IP Simulcast

    3.2.3.3.1 Qu trnh b tr Jitter (Jitter Buffering)

    3.2.3.3.2 Qu trnh b tr sa li Retry Buffering

    3.2.3.3.3 u, nh c im ca truyn thng IP Simulcast trn mng Internet

    3.2.4 Mt sgiao thc, ngn ngv chun k thut sdng trong truyn thng

    a ph ng tin trn mng Internet

    3.2.4.1 Giao thc dnh ring ti nguyn mng RSVP

    (Resource Reservation Protocol)

    3.2.4.2 Giao thc truyn ti th i gian thc RTP (Real-time Transport Protocol)

    v giao thc kim sot th i gian thc RTCP (Real-time Control Protocol)

    3.2.4.3 Giao thc truyn a dng tin cy cao RMP (Reliable Multicast Protocols)

    3.2.4.4 Ngn ng nh du m r ng XML (Extansible Markup Language)

    3.2.4.5 Ngn ngtch h p truyn thnga ph ng tin ng b

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    SMIL (Synchronized Multimedia Integration Language)

    3.2.4.6 Giao thc dng dliu th i gian thc RTSP (Real-Time Streaming

    Protocol)3.2.4.7nh dng dng tin tin ASF (Advanced Streaming Format)

    CH NG 4 : CC GII PHP CUNG CP CH NG TRNH VTV QUAMNG INTERNET

    4.1 Xu thv nh ng iu kin pht trin truyn hnh Internet

    4.2 Cc gii php k thut a VTV ln Internet

    4.2.1 Khi qut vhthng VTV Online4.2.2 Hthng truyn dn v cung c p ch ng trnh VTV qua mng Internet

    4.2.3 Sn xut va ch ng trnh VTV ln Internet

    4.2.4 Tchc c s dliu v vn qun tr dliu, c p nht thng tin

    4.2.5 Giao din Website VTV Online

    4.2.6 Vn thanh ton tr c tuyn qua mng

    4.2.7 Bo mt vm bo an ninh hthng4.3. Gii php k thut tng thcho hthng VTV Onlinep ng nhu cu

    trao i, cung cp t liu truyn hnh qua mng Internet

    K T LUN

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    L I M U

    Trong nhng nm gn y, png nhu cu ngy cng cao ca ng i xem,cng nghtruyn hnhang chuyn sang mt b c ngot m i, l qu trnh chuyntcng nght ng tsang cng nghs. Bn cnh l sbng n, pht trin v sau l xm chim ca cng nghthng tin trong vin thng v trong truyn hnh. Khinhai ngnh cng nghny ngy cng xch li gn nhau h n v xu h ng hi t cxem l mt gii php h p l,m bo s tn ti v pht trin ca chng trong nn kinhtth tr ng. Xu h ng ny cng c khng nh khi m cc nh cung c p Internetang quan tmn vic phn phi cc ch ng trnh truyn hnh, v cc hng truynhnh cng trin khai cc dch vInternet trn mng truyn thng ca mnh.

    Vic k t ni cc ch ng trnh truyn hnh v i h thng vin thng Internet,nhiu hng truyn hnhang to ra cc dch v truyn hnh m i v h p dn, c kh nng png cc yu cu ngy cng cao ca khn gi.

    Sthm nh p t ca cng nghthng tin trong truyn hnh ni chung v qutrnh hi tca truyn hnh Internet ni ringang t ra cho truyn hnh Vit Namnhng c hi v cng l thch thc to l n : c hi to ra nhng b c nhy vt vk thut tin k p v v t cc n c trong khu vc v nguy c c thb tt hu v ph thuc vo n c ngoi vcng ngh, nu chng ta khng nm bt v b qua c hithun l i ny.

    Hin nay, nh nhng thnh tu m i trong l nh vc truyn dn Internet tc cao c bit l cng ngh ng thu bao sbt i xng ADSL (Asymmetric DigitalSubscriber Line) s dng k thut truyn thng bng r ng Broadband cho phpnng tc ti ca cc k t ni Internet lnn 2 Mbps, 5 Mbps v c thcao h n na.

    Bn cnh l thnh tu trong l nh vc nn tn hiu video (MPEG-4) cho phpgim tc truyn ti cn thit xung cn 1,5-2 Mbps. l nhng tin k thutcho shi ttruyn hnh Internet.

    T nhng vn c bn trn,ti i su vo nghin cu cc gii phpcng nghtruyn tn hiu truyn hnh trn mng Internet

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    CH NG 1 : TNG QUAN V TRUYN HNH INTERNET

    --------&&--------

    1.1 Gi i thiu

    Trong khong th i gian tr c, khi m truyn hnh pht sng smt t DVB-T Chu uang g p kh khn, k hoch chuyn i pht sng t ng tsang sb tr hon, v c nguy c v ti mt sn c, gy nhiu thit hi cho cci tc trongl trnh chuyn i t ng t sang s. Nhng cng trong th i im ny, truyn hnh pht sng s trong cc mi tr ng truyn dn khc (nh truyn hnh cp, vtinh...) liv n ln v thu c nhiu thnh tu khquan, khng nh c v tr ca mnh trongthgi i truyn thng gii tr. t c k t qu , khng thkhng nin vai trca cc dch vm i c xy dng trn nn tng ca shi thai cng nghtruynthng hin i lTruyn hnh s v Internet.

    1.2 Cc tin k thut ca s hi tgi a truyn hnh sv Internet

    Spht trin v ti p l sxm chim ca Cng NghThng Tin (CNTT)trong Vin thng v Truyn hnh vn c xem l hai l nh vc t ng i c l ptrong sut qu trnh hnh thnh v pht trin, khin hai ngnh cng nghi p ny ngymt xch li gn nhau h n v xu h ng hi t c xem l gii php h p l,m bocho s tn ti v pht trin ca chng trong nn kinh tth tr ng. Xu h ng ny cng c khng nh khi m cc nh cung c p Internetang quan tmn vic phn phicc ch ng trnh truyn hnh v cc hng truyn hnh cng trin khai cc dch v Internet trn mng truyn thng ca mnh (nhcp, vtinh DTH, smt t ).

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    Internet`

    Data andStreaming media Computer

    Radio andTV program

    BroadcastNetwork

    TV set(viewer)

    TV on the Internet

    Internet on TV

    Hnh 1 : M hnh hi tca truyn hnh v Internet

    Internet l mt hthng c pht trin u tin b i dn nghin cu gia B quc phng Mv cc vin nghin cu nhm chia xcc d liu lin quann quc phng gia cc c s ny. n nay Internet pht trin thnh mt hthng c quim ton cu v i nhng kho lu tr thng tin khng l cho php truy c p bt c lcno, bt c th i im no v th ng min ph cho ng i s dng. Chnh v vyInternet tr nn ph c p r t nhanh ,c bit trong vi nm gn y v i spht trinca bgiao thc TCP/IP cng mt sccng dng trnh duyt Internet. N cho phpng i sdng ddng truy c p, tm kim thng tin trn ton bhthng. Ngoi vncung c p d liu d i dng vn bn,nh ho Internet cng htr truyn dncc dng audio v video - c s ca cc dch v a ph ng tin (Multimedia) trn quim ton cu.

    D i con mt ca cc nh kinh doanh dch v truyn thng, sc h p dn ch yu ca Internet l khnng cho php ng i sdng t ng tc, traoi thng tin v inhau trn phm vi ton cu. Trn c s qun l tng c nhn sdng thng quaa ch IP (ging nhcc a ch c tr ng k theo snh), ng i ta c ththit l p mt th gi i kinh doanh dch v v th ng mi in t (e-service/ commerce) trn phm viton cu, v i nhiu loi hnh kinh doanh/dch vcng tn ti trong mt th tr ngo, bao gm ccc dch v truyn hnh v gii tr. Tuy nhin, do hn chvbng thngca h thng Internet bng h p truyn thng, khi l ng ng i s dng tr c tuyn

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    (online) ti cng th i im li tng vt v t qu khnng vbng thng, qu trnhtruyn thng trn mng sb chm li (thm ch gy ra nghn mng). V vy mt th igian di Internet b nhn nhn nh l mt cng nghkhng ph h p v i truynthnga ph ng tin.

    Mt tr ngi ng k khc cho cc dch v a ph ng tin trn mng l cutrc a hop ca Internet. Trong thc t, cc ni dung truyn trn Internet khng c gi tr c ti p t ngun n ng i dng, m c gi qua mt s cc my ch (server) v thit b nh tuyn (router). Mi sdi chuyn tmt server hay router nci k ti p c gi l mt hop. Mi hop (c thl nhiu hop) slm tng thm th igian vn chuyn v bng thng cn thit cung c p ni dungn ng i sdng cui

    cng. Khi ti cng mt th i im c nhiu ng i cng truy c p vo mt a ch dchvtrn mng, vn str nn nghim tr ng n mc lm nn lng cc bn tham giathng tin, thm ch gy ra nghn mng.

    Sra i ca truyn hnh k thut s, cc thnh tu m i trong l nh vc truyndn Internet tc cao - c bit l cng ngh ng dy thu bao sbt i xngADSL (Asymmetric Digital Subscriber Line) s dng k thut truyn dn bng r ngBroadband cho php nng tc ti ca cc k t ni Internet ln 500 Kbps, 2 Mbps,

    5 Mbps v cao h n na. Cng v i k thut nnnh ng (chun MPEG-4 cho phpgim b t tc truyn ti cn thit ca truyn hnh st4 n 6 Mbps hin nay xungcn 1.5n 2 Mbps) l nhng tin k thut cho shi tny.

    Cc nh nghin cu x hi hc gn y r t quan tmn vn ny v chor ng shi tgia truyn hnh v Internet scho ra i cc dch vMultimedia c vaitr r t l n trong x hi, thm ch tcng t i thi quen gii tr v tiu dng cc sn phm vn ha ni chung, lm thayi cm nhn ca khn givcc dch v truynhnh ni ring.

    1.3 S hi tcc u im ca truyn hnh sv Internet

    Shi tca truyn hnh v Internet c thhin thng qua vic hnh thnhcc mi tr ng mng truyn dn tc cao, c thx l sl ng l n ni dung truynthng Multimedia trn c s giao thc IP mt cch tin cy, hiu qu, an ton v i kh

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    nng t ng tc cng nhiu tnh nngu vit khc. Vthc cht, c thcoi cc yu t sau l sth p ccu im ca cng nghtruyn hnh sv Internet :

    Cung c p khnng t ng tc,iu kin bt buc i v i cc dch v truynthng m i nhVideo theo yu cu VOD, truyn hnh t ng tc

    Cung c p bng thng r ng trn cc mng tc cao, c th truyn i cc nidung truyn thnga ph ng tin c kch th c l n mt cch nhanh chng, hnch ti a nhng nh c im lin quann gi i hn bng thng, th i giantruyn ti ca Internet bng h p truyn thng.

    m bo vic cung c p ni dung mt cch tin cy, c bit l cc ni dungnhng cht l ng tt. Mng Internet truyn thng vn hnh theo nguyn tc thunhn ni dung tt nht mc tt nht c th, c ngh a l ng i sdng cuicng snhn c phn l n cc d liu theo yu cu - nhng gi d liu b h hng, tn tht hay tht lc do cc li trong qu trnh truyn Internet skhng c gi li. V i cc h thng mng tc cao, s dng cc ph ng thctruyn thng tin cy QOS (Quality Of Service) s m bo vic cung c p chong i dng cui cng 100% ni dung yu cu.

    To ngun thu nh p m i: trn cc mi tr ng hi tny cc nh truyn thngc th thay thhnh thc cung c p min ph thng tin trn Internet bng hnhthc kinh doanh truy c p tr tin. Hc thyu cu tr tin cho cc ni dungm hcung c p v ngn chn nhng ng i khng tr tin thu ni dung ca h.

    Bo van ton ni dung trong qu trnh truyn pht, chon khi ni dung ctruy c p b i ng i sdng. Ngoi ra, vic trin khai cc gii php qun l bnquyn d liu sDRM (Digital Rights Management) sbo vcc ni dungngay ckhi n c s dng b i ng i dng, trnh vic truyn b ti p nidung nyn ng i sdng khc.

    Cho php nh truyn thng kim sot chi tit v qun l bng thng t ccserver phn phi trn ton mng, phn bbng thng cho ng i s dng mtcch ph h p nht. iu ny r t quan tr ng khi s l ng ng i ng th i truyc p dch vkh l n (i v i Internet truyn thng, cc giao thc Internet ch cho php kim sot nghn mch mt mc nht nh, nhng cc nh cung

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    c p ni dung vn khng th kim sot c s phn chia bng thng trnmng).

    M ra mt l nh vc sn xut - kinh doanh m i : sn xut, kinh doanh cc thit b thu truyn hnh strn Internet.

    Khai thc th phn khn gisn c ca cc mng truyn hnhang hot ng,cung c p, bxung cc dch v Internet v cc dch vm i cho khi khn gi nytng ngun thu.

    1.4 Khi nim truyn hnh Internet

    Truyn hnh Internet (Internet Television) l cm tdngch dch vcungc p ch ng trnh truyn hnh qua mng Internet v vy n cn c gi l truyn hnhtr c tuyn (Online Television). Hin c hai ph ng thc xem ch ng trnh truynhnh qua mng Internet l:

    Xem tr c ti p theo th i gian thc Real-time (cn gi l ph ng thc Downloadand Play). Vic xem tr c ti p cho php khch hng khng cn ti file ch ngtrnh vmy tnh ca mnh, nhng cho cht l ng hnhnh th p h n. V vych ph h p v i nhng k t ni Internet tc cao, hoc p ng cc yu cukhng cao vcht l ngnh.

    Ti file ch ng trnh vmy tnh c nhn (Download stream-file): ph ng thcny s m bo c cht l ng hnhnh ch ng trnh, nhng li mt th i gianch i v khng p dng c cho cc ch ng trnh truyn hnh tr c ti p.

    Nhn chung chon nay, do nhng hn ch v c s h tng truyn dnInternet, ph ng thc ti file ch ng trnh vmy tnh c nhn c v c ng dng phbin h n v c nhiu ng i bit n v i tn gi truyn hnh theo yu cu VOD(Video On Demand). Cc ch ng trnh truyn hnh (hay cc bphim) sau khi csho slu tr d i dng cc file ch ng trnh (m thanh v hnhnh) ti my ch (server). Ng i xem c thchn cc ch ng trnh m mnh thch tbt k v tr no c

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    k t ni Internet, ti bt k th i im no thng qua mt ng tc click chut n ginvo file trn cc website ca nh cung c p dch v. y th ng l cc dch v truyn hnh tr tin v i hnh thc thanh ton thu bao, tr tin theo l ng ch ng trnh xem (pay per view) hoc tr theo th i gian thc s dng dch v (pay per minute).

    Ch ng trnh truyn hnh Internet tr c ti p u tin chnh thc xut hin ngy13/5/2000 ti Stockhom (Thy in), l ch ng trnh ca nhc Eurovision SongContest do EBU tchc hng nm. Hin nay, khi c s htng Vin thng- Internettc cao tr nn phc p th truyn hnh tr c tuyn c xem l ph ng thc chiu qukinh tnht phsng cc ch ng trnh truyn hnh trn phm vi ton

    cu.

    1.5 Nh ng ng dng ca truyn hnh Internet

    Mt trong nhng kha cnh h p dn ca truyn hnh Internet l n cho phpcung c p ccng dng v i c s cng nghv mc u t t ng ng. Truyn hnh

    Internet c thk t h p v i mt mng IP bng r ng m i (hoc sn c)cung c p v igi th p h n so v i gi cung c p ni dung truyn hnh th ng mi. Mt s ng dngquan tr ng ca hthng truyn hnh Internet bao gm :

    Video theo yu cu (VOD) : v i truyn hnh Internet mt l ng l n ni dungch ng trnh c th c lu li trong cc Streaming Server (gm film, ca nhc,ththao, gii tr ). Ng i xem c thtm kim v xem ch ng trnh yu thch

    ca mnh vo bt c lc no. Ngoi ra, ng i sdng cn c cung c p mtgiao din xem nhng ch ng trnh ny khi thun tin v i skim sot nh v i PVR.

    To ch ng trnh truyn hnh c nhn : tcc mc ch ng trnh truyn hnh mkhch hng xem hoc cc ch ng trnh yu thch, h thng truyn hnhInternet c th to ra mt danh sch cc ch ng trnh c c nhn ho chotng thu bao.

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    Gim st qua video : mt skhch hng cn gim st mt i t ng cthr ithu li videos dng vsau (nh cnh st giao thngt camerakimsot tnh hnh giao thng v ghi li cc xe vi phm lut) .

    Tin tc th i s v th i tit theo yu cu : truyn hnh Internet cung c p ccch ng trnhc bit nh tin tc th i sv th i tit theo yu cu. V i dch v ny, thu bao c thxem cc tin tc pht tr c y mt cch tu theo yucu.

    Th ng mi in t : ccng dng ny (khng phi l dng hnhnh) c th c nng cao nh s dng cc cng ngh truyn dn ging nh truyn hnhInternet. Khnng truyn dn ny c c hi mangn nhng ngun doanh thum i cho cc cng tyin thoi (ng i xem truyn hnh c thbm nt iukhin txa t mua hng, hay kim tra ti khon ca mnh ngn hng)

    Truyn hnh t ng tc : truyn hnh t ng tc lng dng tt nht ca truynhnh Internet, n khng ch lm cho ni dung ca ch ng trnh truyn hnh c nng cao, m cn cho php t ng tc hai chiu gia ng i xem v ich ng trnh truyn hnh,em li sphong ph v cun ht khn gi. Khn gi t tr ng thi thu nhn thng tin mt cch th ng khi xem truyn hnh truynthng, schuyn sang ch ng h n v c cm nhn nh c ho mnh voch ng trnhang xem. Vthc cht, y l sk t h p gia vic xem truynhnh truyn thng v i cc hot ng t ng tc c thc hin thng qua knhthng tin phn hi da trn mt hthng mng (nhInternet, cp hay vtinh).

    Tnm 2001, hng BBC thc hin cc ch ng trnh truyn hnh tr c ti p v ini dung t ng tc khu vc sn xut IPA (Interactive Production Area) cnhStudio ththao trung tm BBC Television, truyn pht thng qua khu vc dch

    v a lung MSA (Multistreaming Area), cho php truyn phtng th i ccch ng trnh ny trn mt sknhu tin. Nhiu t liu, ch ng trnh traoic tnh cht th i s v i ni dung t ng tc cng c pht km cc ch ngtrnh chnhNhng phn ng tch cc i v i dch vny tpha khn gitiAnh trong th i gian qua cho thy truyn hnh t ng tc c thl mt gii phph p l cc hng truyn thnga dch vbsungn ng i xem, gip duytr v tng th phn trong qu trnh pht trin.

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    Ti M, cc iu tra thng k c tin hnh trong vi nm gn y cng chothy truyn hnh t ng tc tr thnh mt ngnh cng nghi p, ng vai trquan tr ng trong vic thc y tin b cng nghv tng l i nhun cho gi itruyn thng. Ti Vit nam loi hnh ny cng ang c y mnh pht trinv ha hn sthu c nhng k t qukhquan.

    Hnh 2 : Gi i thiu trang Web tr c tuyn ca i THVN

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    Thit l p mng truyn thng ni b trn c s cc mng truyn dn truyn hnhs: v i k thut mng ringo VPN, cc cng ty c nhiu chi nhnh, nhiu vn phng trn mt khu vc hay thnh phc thsdng cc mng truyn hnh s (phbin hin nay l truyn hnh cp, hay qua ng ADSL)cung c p thngtin v tin tc c p nht cho cc c s ca mnh. Khi c hthng truyn thng s ny cng c vn hnh v kim sot t ng tcc mng ni bLAN.

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    CH NG 2 : KHI QUT VCNG NGH TRUYN HNH INTERNET

    --------&&--------

    2.1 Gi i thiu vmng truyn hnh Internet

    2.2.1 Cu trc mng

    Truyn hnh Internet l mt gii php cho php cc nh cung c p dch v lcc ch ng trnh truyn hnh v video qua mng IP bng r ng n cc tivi ti cc h gia nh hoc my tnh. Qua cc mng truyn hnh Internet, nh cung c p dch vcthcung c p cc dch vt i khch hng nh : VOD Video theo yu cu, truyn hnht ng tc ITV, dch vd liu, tr ch i truyn hnh qua mng, gio dc txaGii php truyn hnh Internet hon chnh bao gm t nht 6 yu t : Content Creator,Server Streaming, thit b chuyn mch, mng IP bng r ng, Set-top-box vMiddleware

    Mng IP b ngr ng

    `

    `

    Streaming Server

    Thi t b chuy nm ch

    Lu ng ch ngtrnh

    Gim st , iukhi n ho t ng

    Set-Top-Box

    TV

    PC

    Conten Creator

    Hnh 3 : Hthng truyn hnh Internetin hnh

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    Content Creator :y l mt thit b u cui, hot ng nhmt Gatewaytruyn thng. Ni dung video c chuyn t i Content Creator tr c khi c phn bqua mng. Nu tn hiu n dng analog n sm ho thnh tn hiusMPEG. Nu tn hiu n l dng s (nhDVB-S), n sgii iu ch, tchknh v chuyn m cc lung tn hiu. Lung d liu ny sau c gi nStreaming Server.

    Streaming Server : thc hin nhiu chc nng (nh nhn cc ni dung sm i c m ho tContent Creator, truyn ti p hoc lu li, cc server lu ginidung c m ho bng k thut s v chuyn n qua mng IP bng r ng.Streaming Server cng c chc nng png s t ng tc v i cc thu bao v

    cc yu cu. Streaming Server c khnng trin khai cao, ddng x l cc li,dung l ng hthng l n v mc thng l ng cao.

    Thit b chuyn mch (Switch Media) : l thit b iu khin ca chthng,n gim st viu khin s hot ng ca Content Creator v StreamingServer theo th i gian thc. Switch Media cng theo di s lu tr cc phnvideo c phn phi gia cc Streaming Server v nhn cc yu cu ca thu bao, h ng ccon d liu (data segment)n Streaming Server v phi h p

    hot ng ca Streaming Server. N cng cung c p giao din cho h thngqun l, cho php cc nh vn hnh l p cu hnh, gim st viu khin ccStreaming Server v Content Creator.

    Mng IP bng r ng : l mng truyn ti cc lung d liu. Khc v i cc mngtiu chun IP cung c p dch vkhc, mng IP bng r ng c di tn r ng h nnhiu v i s nng cao cht l ng dch vQOS. truyn pht truyn thnghiu quh n, n h tr IP n h ng va h ng ng th i h tr StreamingIP viu khin cc giao thc. ng tr c ca mt hthng nhvy l mngcp v i chuyn mch l p 3. Mng phn phi c thl bt cph ng thc bngr ng no bao gm cDSL hoc TTT[x].

    Set-Top-Box : nhn cc lung tn hiu qua cc thit b CPE (Customer PremiseEquipment) nhmodem v gii m nhin th trn mn hnh tivi. Ngoi ran cung c p mt giao din ng i dngng i s dng c tht ng tc v icc Server video. Cui cng, Set-Top-Box cung c p mt giao din analog chocc TV analog (ang sdng phbin hin nay) v n thc hin chuyn i d dng tTV sra TV t ng t.

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    Middleware : l phn mm k t h p cc phn khc nhau ca truyn hnh Internetthnh mt h thng hon chnh. N qun l thit b, knh v lch pht sngtruyn thng, tnh gi an ninh v truy nh p ciu kin. Ngoi ra Middlewarecn c chc nng qun l hthng v cc chc nng qun l khc.

    2.2.2 Cc chun mng

    H thng truyn hnh Internet da trn cc chun cng nghi p c thl p tvo cc mng hin ang c mt cch ddng v nhanh chng cng nhvic qun l

    hiu quh n trong th i gian di. Do cc chun c xu h ng thayi theo th i giannn l t ng l dng mt gii php truyn hnh Internet c thit k theo mt trung gianhot ng v i bt k chun no ca ngnh vo mt th i im bt k .

    2.2.3 Khnng nng cp mng

    Cc gii php truyn hnh Internet c khnng nng c p bt k p nhng yucu trong t ng lai, khnng nng c p c th c xc nh theo s thu bao, s l ng (c thc nhiu lung/1 thu bao) v dung l ng hthng hay sgi cung c pni dung s p ng cc yu cu khc nhau. Cc ph ng phpp ng yu cu nngc p mng truyn hnh Internet l mng t p trung, phn phi hay k t h p chai. V icu trc t p trung, tt cni dung c cha trong Streaming Server ti mt a imtrung tm, cc lung d liu theo yu cu c truyn t trung tmn khch hngqua mng cp ng tr c v mng truy nh p.

    V i cu trc phn tn, ni dung c lu tr trong Streaming Server ti cca im khc nhau, mi a im c chuyn mch ring, tt ccc a im c k tni qua mng cp bng r ng. Trong cu trc ny, cc lung tn hiu video tContentCreator c phn phi ti Streaming Server qua ton mng truyn hnh Internet,Switch Media trong mng c nhim v tm ra topo ca mng v kim sot v tr tng phn ca ni dung trong ton bh thng. Ni dung c sao li n mt a imkhc theo yu cu da trn thut ton d tm.

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    i v i hthng hn h p, ni dung c lu li trong cc Streaming Server,tt ccc a im c k t ni qua mng cp bng r ng ngoi tr cc video server trong mng ch cha nhng ni dung chnh trong khi cc video server ti a imtrung tm c vai tr nhmt my chlu tr tt cni dung. Cc lung video ContentCreator c gi n my chlu tr trung tm, sau ni dung c phn phi ntt ccc a im da trn thut ton d tm v i cu hnh hn h p, khch hng c phc v b i cc my server gn nht. Nu ni dung yu cu khng c trong server trong khu vc th s c chuyn tserver lu tr trung tm.

    Mt vn l n i v i truyn hnh Internet l khch hng skhng ch p nhnxem TV qua mng Internet nu cht l ng ca n th p h n xem TV qua cp hay v

    tinh. Do, mng truyn hnh Internet phi c khdng hon ho tuyt i, khngc tr ngi no trong hot ng ca cc dng d liu. Ngoi ra mng truyn hnhInternet cn phi bao gm vic m bo cht l ng QOS trong ton bdch vv ccthit b truy nh p IP bng r ng phi h tr QOSa h ng v nng c p ln VDSL haycc cng nghc tc bt cao.

    2.2.4 Trin khai lp t mng

    Csu phn ca h thng truyn hnh Internet t ng tc v i nhautruyn pht cc ch ng trnh tr c ti p hoc thu tr c, cc ch ng trnh theo yu cu hoc k th p chai loi.

    Tn hiu truyn hnh a tr c ti p vo Content Creator c m ho/chuyn m thnh dng MPEG v gi n Streaming Server, v ti p tc chuyn ccdng tn hiu n mng bng r ng v lu vo trong cc thit b lu tr (nh cng).Mng IP bng r ng pht cc lung tn hiu nyn thit b c s ca khch hng, ccthit b ny nhn tn hiu v gi chngn Set-Top-Box (STB). STB gii m cc tnhiu v pht li trn TV. Khi khch hngp ng li cc iu khin nh PVR catruyn hnh Internet (nhkhi nhn nt Pause) th dng t ng tc snhsau :

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    Disk

    TV Signal

    Media Switch

    Media Switch

    Data

    Control

    Remote controller

    TV

    Set-Top-Box

    Broa banNetwork

    StreamingServer

    ContentCreator

    Status

    Hnh 4 : Dng t ng tc gia cc bphn khi pht ch ng trnh video theo yu cu

    Khch hng gi mt yu cu n STB quaiu khin txa, STB snhn yucu v chuyn n n Switch Media xcnh Streaming Server v i Media cyu cu, h ng yu cu n cc Streaming Server v iu khin hot ng ca ccthit b ny. Streamingp ng li cc yu cu bng cch ngng cung c p dngStreaming.

    Cc yu cu ti p theo ca khch hng c gi tr c ti p n Streaming Server v c x l ti cho n khi mt thao tc chuyn ti p n mt a im truynhnh tr c ti p c thc hin hay khch hng chuyn qua knh khc. Khch hng lachn xem mt ni dung lu, STB nhn yu cu v gi n tr li Switch Media,Switch Media xcnh Streaming Server v i ni dung c yu cu v gi yu cun Streaming Server , ng th i phi h p cc thao tc, n s p ng li yu cugi l ni dung c lu v gi n mng bng r ng n i ni dung c truyn nkhch hng, cc yu cu ti p theo ca khch hng c gi tr c ti p n StreamingServer v c png ti chon khi khch hng chuyn sang ch ng trnh khc.

    2.2.5 Chi ph

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    u t l n vo c s htng hthng l mt kh khn cho vic a dch v vo khai thc v ph thuc vo cng nghm i. cnh tranh v i cc dch v truynhnh khc,iu bt buc cc dch vtruyn hnh Internet phi c chi ph trin khai l pt v qun l th p. S la chn cc cng nghbng r ng cngnh h ng n chi phl p t. V nhgii php IP DSLAM m i c gi th p do phi loi bl p gia ATM cchi ph cao, nn gim chi ph cung c p dch v n tng thu bao v gim th i gianhon vn. Ngoi ra v i vic s dng ng dyin thoi c sn k t h p v i cngnghADSL slm gim chi phu tv tng c dung l ng ti ch ng trnh.

    2.2 Cng nghtruyn hnh Internet

    D i gc cng ngh, c thcoi cc dch v truyn hnh Internet nh s pht trin mc cao ca truyn thng Internet (cn gi l Webcasting) v l b c pht trin ti p theo, ni ti p cng nghWeb trong hai th p k tr c y, mt cngnghc khnng a thng tin ln phm vi ton cu trn World Wide Webn ng is dng Internet mt cch nhanh chng v hiu qukinh tcao nht. iu khc bitchyu ca cng nghtruyn hnh Internet so v i cng nghWeb tr c y l thngtin truyn i khng cn ch c thhin d i dng vn bn hayhona, m d idng videonh ng th i gian thc v i cht l ng ch p nhn c. Cng nghnycn c gi d i mt s tn khc nhVideo Streaming, WebstreamingNi khci, y l sk t h p gia cng nghWeb thng th ng v cng nghStreaming. Khcv i vic download sdng trong k thut web thng th ng i hi lu cha y d liu d i dng cc file trongcng my tnh tr c khi hin th, Streaming l cngnghcho php gi lin tc tn hiu mang cc d liu nh ng thng qua Internet v i

    phn mm c bit, gip my tnh gii m tn hiu ngay khi n c nhn v hin th dliu gn nhngay l p tc khi c truyn n theo tr t tchnh xc.

    Vic a ch ng trnh truyn hnh qua mng Internetn ng i xem cthc hin qua cc giaion to ch ng trnh, truyn dn phn phi v hin th ch ngtrnh ti cc thit b hin th ca ng i xem.

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    `

    Server qu n lUser

    StreamingServer

    Webserver

    Truyn hnh theoyu c u

    Truyn hnh tr c tip

    User

    Internet :UnicastMulticastSimulcast

    To ch ng trnh Truy n d n v phn ph i Hin th

    Hnh 5 : To v phn phi ch ng trnh truyn hnhn ng i xem qua mng Internet

    2.2.1 To ch ng trnh truyn hnh

    Hai k thut Webstreaming c sdng trong giaion ny l k thut On-Demand (Truyn hnh theo yu cu) v k thut Live Streaming (Truyn hnh tr cti p)

    2.2.1.1 Truyn hnh theo yu cu

    C hai k thut c sdng l :

    Download vmyxem : cc file nn s c ti vmy tnh ng i dng vmt phn mm s c s dng hin th ni dung (ph ng php ny cgi l k thut Streaming HTTP).

    Hin th ni dung th i gian thc : s dng streaming th i gian thc (real time

    streaming) truyn thng ni dung tr c ti p t mt server c chn b i

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    ng i sdng, gip hc thxem ni dung tc th i. V i k thut ny khngc file no c lu tr hay nh trong qu trnh Streaming. Do ng i dngkhng thlu tr , copy hay truyn pht li ni dung v dng d liu streamingkhng chy vo a ca my tnh v d liu b loi bsau khi hin th, nn cthhn ch c vic sao chp bt h p php ni dung truyn pht trn mng

    Mt trong cc yu cu k thut quan tr ng nht i v i hthng truyn hnhtheo yu cu l khnng trnh duyt, tm kim nhanh ccon video, gip ng i xemtm thy cc thng tin lin quann cc ch ng trnh m hquan tm v gip h ngnh p tr c ti p n a ch lu tr cc ch ng trnh ny.iu ny to iu kin chong i xem ti p cn li cc thng tin (ni dung ch ng trnh) tri qua hay b b l khng xem. Thm vo, trn c s danh sch cc ni dung truyn thng c thng bo d i dng danh mc cc ch ng trnh, cc khn gicng c thla chn xem nidung g v xem vo th i im no thch h p nht. iu ny lm tng hiu quca ccch ng trnh truyn hnh, tng gi tr gia tng ca cc ni dung truyn thng trong mtth i gian di h n, v gim ti cho bng thng v trnh hin t ng k t ni ng th i canhiu ng i xem vo cng mt ch ng trnh. Ngoi ra, v i vic bxung cc tnh nng

    khc nh tua nhanh, chm, ph ng php t ng tc, chat rooms, dch vquay cameraa ph ng, phng to hay thu nh nh.Truyn hnh t ng tc str nn ngy cngh p dn h n i v i khn gi.

    2.2.1.2 Truyn hnh tr c tip trn mng

    Truyn hnh tr c ti p trn mng l mt k thut Webcastingtruyn d liutrn Internet m khng cn phi i chon khi tt cfile c ti vmy tnh cang i dng. K thut nyi hi ng th i ba yu tsau :

    Thit bm ho bin i tn hiu audio/video t t ng tsang sv nn cc files truyn trn mng

    Server cung c p cc dng dliu n ng i xem

    Thit b hin thm ng i sdng dngxem cc ch ng trnh truyn hnh

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    to khnng ghp audio v video vo cng mt dng truyn ti, cng ngh

    streaming s dng phn mm nn tn hiu truyn i, gii nn tn hiu hin th trn mn hnh ng i xem theo mt tr t tchnh xc lin tc ng i xem c thxemni dung hu nh tc th i. Bt cmt khong tr ng no (gi d liu b tht lc hay b li khng gii m c) trong dng d liu slm cho hnhnh hay m thanh tr nnkh hiu. m bo s thnh cng ca qu trnh m ho, truyn ti, thu nhn, giim v hin th li theo mt tr t tchnh xc cn sdng cc server mnh, c tc x l cao v i y bng thng cn thit x l v cung c p cc dng truyn ti nidung ch ng trnh.

    2.2.2 Truyn dn v phn phi

    Cc gii php k thut cho truyn thng Internet bao gm :

    IP Unicast : c sdng truyn d liu (hay gi d liu) tmt my phtn mt my thu n gin.

    `

    `

    `

    My ch

    My trm

    My trm

    My trm

    Mng

    IP Broadcast : s dng gi d liu tmt my phtn ton bmng con

    Subnetwork.

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    `

    `

    `

    My ch

    My trm

    My trm

    My trm

    Mng con

    IP Multicast : c dngcung c p d liu tmt my phtn mt nhm

    cc my thu c cit theo mt cu hnh thng nht, cc thnh vin ca mtnhm ny c ththuc cc mng phn tn khc nhau.

    `

    `

    `

    My ch

    My trm

    My trm

    My trm

    Mng con

    Mng con

    My trm

    `

    Multcast Router

    IP Simulcast : l mt gii php mang tnh cch mng m i c pht trin b ihng Pipe Dream Inc. Cng nghm i ny bao gm giao thc truyn thngInternet IP Simulcast, cc thut ton nn video v audio m i cho php truyn pht d liu video v audio th i gian thc ti cc tc bt r t th p m vn m bo cht l ng nh v m thanh kh cao, hnhnh c hin th trn ton b mn hnh.

    2.2.3 Hin th

    Tr c y, s a dng ca cc thit b hin th l mt vn lm au u ccnh cung c p truyn thnga ph ng tin qua mng. Ngy nay, nhng thnh tu phttrin v t bc ca cng ngh thng tin, mng Internet v s ra i ca cc chun

    truyn thng trn nn tng truyn thng mng Internet TCP/IP, vn ny hu nh

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    khng cn l tr ngi ng k na. V i sphc p ca Internet, s ra tng ca dungl ng bnh , v tc x l ca cc chp tng nhanh, vn gii m v hin th cctruyn thng dng Multimedia trn Internet khng cn lc quyn ca cc thit b phn cng na.

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    CH NG 3 : CC CNG NGH TRUYN THNGA PH NG TINTRN MNG HIN NAY

    --------&&--------

    3.1 Khi qut vmng Internet v m hnh TCP/IP

    3.1.1 Mng Internet

    3.1.1.1 Gi i thiu vInternet

    Nm 1995, v i s tham gia tvn ca ban lnho Internet v hi p hi IPR (hi p hi quyn s hu tr tu); FNC (Federal Network Council) nht tr thng qua mtngh quyt t nh ngh a ln thut ng Internet. V Internet c hiu l hthngthng tin ton cu png cc yu cu :

    c ni v i nhau h p l bng mt khng giana ch c o da trn giaothc IP.

    C thto iu kin cho cc my tnh giao ti p v i nhau thng qua bgiao thcTCP/IP.

    Cho php s dng, truy c p cc dch v cao c p c lu tr , trao i trnmng.

    Tm li, mng Internet l mng ca cc mng my tnh, hot ng truynthng tun theo bgiao thc TCP/IP.

    3.1.1.2 Cc ng dng ca Internet

    Internet khng ch l mt mng k t ni ton cu m h n thna n l mngx ng sng to c s cho vic truy c p n r t nhiu dch vkhc. l mt cu trc

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    k t ni r t a dng cc mng cng cng v cc mng ring. K t ni ca ng i sdngn cc mng ny c tht do khng gi i hn hoc cng c thph thuc vo tngk t ni v mc tr tin cho tng k t ni . png nh p pht trin ca Internet,cc nh cung c p dch v cho ra i cc dch vgi tr gia tng nhm phc vcci t ng sdng Internet. Nhng hnh thc dch vny kh m i m, nhng chng takhng thphnhn c tc dng ca chng nhmt cng ch tr c lc khngth thiu. Dch vny lun c m r ng, ci tin, nng c p, v ngy cnga dng phong ph nh:

    Video qua mng

    in thoi qua mng

    Hi ngh qua mng

    Fax qua mng

    Nhn tin

    Webhosting

    3.1.2 M hnh TCP/IP

    TCP/IP thc cht l t p giao thc cng lm vic v i nhaucung c p ph ngtin truyn thng lin mng. Nm 1981, m hnh TCP/IP version 4 c hon tt v c ph bin r ng ri cho ton bmy tnh s dng h iu hnh Unix. SauMicrosoft cng a TCP/IP tr thnh mt trong nhng giao thc cn bn ca h iu hnh Windows 9x .n nm 1994, mt phin bn m i IP version 6 ra i ci

    thin nhng hn chca IP version 4. Nu IPv4 ch s dng 32 bta ch (chiathnh 4 vng - mi vngng v i mt byte) th IPv6 s dng 128 bta ch - tc lg p 4 ln s a ch ca IPv4.

    Nhngu im khc ca IPv6 l :

    Khnng ci thin v nh tuyn hiu quh n do c sdng cc mou th n. Mc d tr ng a ch di g p 4 ln nhng IPv6 Header ch l n h n IPv4Header c 2 ln, do vic chnh sa cc tham smou (Header file) v nn

    chng hiu quh n IPv4.

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    C shtr bo mt (IP security)

    c htr tnh nng ding

    C mc qun l cht l ng dch vcao h n Nu trin khai IPv6 th cn mt l ng th i gian kh l n cc nodes IPv4 v

    IPv6 cng tn ti v truyn tin. Yu cu t ra l phi c c chchuyn i va mmdo li va mnh c thchuyn i IPv4 thnh IPv6. Trn thc t, lc l ng ctrch k thut Internet (IETF) trin khai hng lot cc k thut lin k t IPv4 vIPv6, nhng k thut ny c thtm tt gm 3 loi sau :

    K thut ng hm : cc ng hm c th c s dng nh tuyn ccgi gia cc my chIPv6 qua mng IPv4 bng cch chn thm phn mouca IPv4 vo gi IPv6.

    K thut chuyn dch : nhng bghi dch c dnglin k t gia IPv4 vIPV6, cc bghi dch - giao thc a chmng (NAT-PT) v thut ton ghi dchkhng tr ng thi IP/ICMP.

    K thut ngn x p : cIPv4 v IPv6 cng tn ti song song trn cng mt mych.

    M hnh TCP/IP c chia ra lm 4 l p (layer) v c t ngng v i cc l ptrong m hnh OSI 7 l p nhsau :

    3.1.2.1 Giao th c mng IP

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    IP (Internet Protocol) l giao thc k t ni khng lin k t. Chc nng chyu

    ca IP l cung c p cc dch vDatagram v cc khnng k t ni cc mng con thnhlin mng truyn d liu v i ph ng thc chuyn mch gi, thc hin tin trnhnh a ch v chn ng. IP Header c thm vou cc gi tin v c giaothc tng d i truyn theo dng khung d liu (frame). IPnh tuyn cc gi tin thngqua lin mng bng cch sdng cc bng nh tuyn ng tham chiu ti mi b cnhy. Xcnh tuyn c tin hnh bng cch tham kho thng tin thit bmng vtl v logic nhARP (Address Revolution Protocol - giao thc phn gii a ch). Ccchc nng chnh l :

    nh ngh a cu trc cc gi d liu l n v c s cho vic truyn d liu trnInternet

    nh ngh a ph ng thc nha ch IP

    Truyn dliu gia tng giao vn (transport) v tng mng (internet)

    nh tuyn chuyn cc gi dliu trong mng

    Thc hin vic phn mnh v h p nht cc gi d liu v nhng/tch chngtrong cc gi dliu

    3.1.2.2 Giao th c TCP

    TCP (Transmission Control Protocol) l giao thc k t ni lin k t, ngh a l cnthit l p lin k t gia mt c p thc thTCP tr c khi chng traoi d liu v i nhau.

    TCP cung c p khnng truyn d liu mt cch an ton gia cc my trong hthngcc mng. Ngoi ra cn cung c p chc nng kim tra tnh chnh xc ca d liu khin v truyn li dliu khi c li xy ra. Cc chc nng khc nh:

    Thit l p, duy tr, k t thc lin k t gia hai thc th

    Phn pht gi tin mt cch tin cy

    nh sthtcc gi dliu nhm truyn dliu mt cch tin cy

    Cho phpiu khin li

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    Cung c p khnng a k t ni v i cc qu trnh khc nhau gia tr m ngun vtr m ch thng qua sdng cc cng

    Truyn dliu sdng c chsong cng

    3.1.3 Gi i thiu cng nghADSL

    Cng nghADSL (Asymetric Digital Subscriber Line) c pht trin t unhng nm 1990 khi xut hin nhu cu truy c p Internet tc cao, cc dch v tr ctuyn, video theo yu cuADSL cung c p tc truyn dn khngi xng : t16- 640 Kbps v i lung ln v t i 8 Mbps v i ng xung (t tng i n khch hng)v i khong truyn ti a l 50 km. u im ca ADSL l cho php ng i s dngdng ng th i ng dyin thoi cho chai loi dch v l thoi v s liu vADSL truyn min tn s cao (20 Khz - 1 Mhz) nn khngnh h ng t i tn hiuthoi. Cc b lc c t hai u mch vngtch tn hiu thoi v s liu theohai h ng khc nhau. Mch ADSL to nn ba knh thng tin i dy thu bao : mtknh tc cao t tng i t i thu bao, mt knh tc trung bnh hai chiu v mt

    knh thoi hoc mt knh N-ISDN. Modem ADSL t ng thch v i truyn dn ATM,giao thc IP bng vic thayi tc truyn dn ph h p v i cc mu ca ATM, IP.

    Mt dng ADSL khc gi l ADSL.lite hay ADSL khng sdng bchia tinh thu bao xut hin tnm 1998. K thut ny khngi hi b lc pha thu bao nn gi thnh thit b v chi ph l p t gim i gip cho tc trin khai Internet bng thng r ng nhanh h n nhng tc lung ch cn 1,5 Mbps.

    Thng 7/2002 ITU-T ban hnh tiu chun u tin vADSL2 trong khuyn

    nghG.992.3 nhm ci tin tt c ng dng trn ADSL cvthoi v sliu :

    ADSL2 h tr ch truyn dn ng bST, ch truyn dn bt ng b ATM, ch truyn dn Packet v h tr thoi khng gi (thoi c a vodng dliu ADSL2 khng cn qua bIAD).

    Mc tiu ca qun l ngun ADSL2 thc hin tit kim nng l ng cho tnhnng always on ca ngun ADSL.

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    ADSL2 thayi vdi tn truyn dn theo hai chiu downstream v upstreamv i s phn bmt phcng sut thch h p trn cc di bng tn. Nh s ci thin ny mdi ng dy cho mt tc c nh tng n 300m.

    ADSL2 cho php nhiu ng dy ADSL2 to thnh ng dy ADSL2 tc cao. Cc ng dy ADSL2 ghp c sdng thay thcho gii php VDSLv i cly di h n nhng v i s i dy nhiu h n.

    ADSL2 s dng c ch thchng tc SRA (Seamless Rate Adaption) cho php thayi tc d liu m khng b ngt qung, khng b r t mch, khng b nh h ng t i t ssai bt.

    3.2 Cc ph ng php truyn thng a ph ng tin

    i v i ccng dng truyn thng Internet cho truyn hnh, hnh thc phn phi d liu mt n nhiu im l cn thit, trong dng d liu cn c truyn itmt my phtn nhiu my thung th i, nhng khng c phpi n ton b mng con. V l do ny nn gii php IP Broadcast th ng khng c sdng trong

    truyn hnh Internet. Ccng dng truyn hnh Internet hin nay th ng s dng ph ng php IP Unicast v IP Multicast v IP Simulcast, trong IP Multicast hin lgii php phbin nht hin nay. Tuy nhin do ccu im h n hn ca mnh, gii php IP Simulcast c dbo sl cng nghchyu ca truyn hnh Internet trongvi nm s p t i.

    3.2.1 IP Unicast

    Mt s ng dng truyn thng Internet cho truyn hnh giaion u s dng ph ng php truyn d liu IP Unicast. Trong tr ng h p ny, cc truyn titheo dng c nh h ng k t ni c sdng phn phi d liu n mi mythu mt cch ring l.

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    `

    `

    `

    Sender

    Router Router

    Inter Network Receiver

    Router

    D2

    D3

    D1D2

    D2D3D3

    D2

    D1

    D3

    D1

    D1

    Hnh 6 : Gii php truyn thng IP Unicast

    Ccng dng ny hin cn mang nhiu hn chv hin nay t c ng dngv nhng l do sau :

    Bng thng ca mng b lng ph

    Dch vkhng thm r ng phc vkhi sl ng my thu tng ln

    Khng thsdng trong cc thit b gi i hn th i gian, do scung c p n mimy thu phi theo trnh tx p hng.

    3.2.2 IP Multicast

    3.2.2.1 Truyn thng IP Multicast trn mng Internet

    Ph ng php IP Multicast cng cho php truyn d liu t mt my phtsender n nhiu my thu, nhng khng ging nh IP Unicast, con s cc bn sao(copy) d liu ging nhautruyn i c gim mc ti thiu. Tt ccc my thuca mt nhm multicast (l p mng D) c ci t cu hnh ging nhau. My phtsender truyn mt gi IPn mt a ch multicast v cho php gi chuyn ti p mt bn copy ca gi d liu n my chca mi nhm. Nh vy con s cc bn copydi ra qu mc cn thit truyn n cc mng c p d i (subnet) c gim thiu v IPMulticast c hiu quh n IP Unicast, do tit kim c nhiu bng thng my ch server.

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    `

    `

    `

    Sender

    Router Router

    Inter NetworkReceiver

    Router

    `

    `

    Router

    DD D

    D1

    D2

    D3

    Receiver 1

    Receiver 2

    Receiver 4

    Receiver 5

    Receiver 3

    Hnh 7 : Gii php truyn thng IP Multicast

    Giao thc c sdng trong truyn thng IP Multicast c thc hin ti ccRouter mng, khng phi trong cc my chServer. Cc Router mng t ng to ramt bn copy ca mi gi multicast cho mi my thu. Vic nh tuyn trong truynthng IP Multicasti hi cc Router c bit : cc router trung gian gia my phtsender v cc my thu receiver cn phi c khnng IP Multicast.

    IP Multicast khng phi l mt ph ng thc truyn thng k t ni nh h ng :my pht sender gi d liu n nhiu my thu thng qua giao thc gi d liu ng idng UDP (User Datagram Protocol). UDP cng l mt giao thc thuc l p giao vn(Transport Layer) nhTCP. Nhng khc v i TCP, UDP l loi giao thc khng link t, khngi hi phi thit l p lin k t logic gia hai thit b trao i thng tin v inhau, m cho php truyn s liu thng qua shiu cng m khng cn thit l p mt phin k t ni logic. Khnng ny cho php rt ngn c th i gian truyn s liu,nhng li khngm bo chc chn gi d liu c gi i s n ch. Nu mi lixut hin trong qu trnh truyn th gi d liu sb hub. Vic phc hi cc gi d liu b mt s c thc hin thng qua cc yu cu phn hi n my pht sender (iu ny tt nhin slm cho s truyn thng phc t p h n hnh trn v ny sinhyu cu bng thng mng cao h n).

    Trong nhiu tr ng h p, khi cc my thu nm trong cc mng con c ngncch v i cc mng Internet bng cc bc t ng la (fire wall), nhng bc t ng lany cn c c khnng v c cit cu hnh cho php cc dng IP Multicastiqua.

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    Mng con gi Mng con nhn

    Gi ng dng Multicast

    Nhm giao thcUDP,IP,ICMP,IGMP,TCP/IP

    H iu hnh mng

    Nhn ng dng Multicast

    Nhm giao thcUDP,IP,ICMP,IGMP,TCP/IP

    Giao din mng Giao din mng

    H iu hnh mng

    Internet

    ng dng Multicast

    Cng ngun, cng n, a ch Macgi v nhn

    Multicast Router

    Hnh 8 : Mng truyn thng v i cc phn tc khnng IP Multicast

    c ththu c v hin th cc dng truyn thng IP Multicast cc my thucn png cc yu cu sau :

    H tr truyn thng (truyn v nhn d liu) IP Multicast theo nhm giao thcTCP/IP

    Cit phn mm htr giao thc mng Internet IGMPgi cc yu cu hy bhay tham gia k t ni multicastn cc my thu multicast trong nhm.

    Card giao din mng c th lc mt cch hiu qucc a ch l p k t ni d liu mng Lan c nh xtn a ch.

    3.2.2.2nh tuyn trong truyn thng IP Multicast

    nh tuyn cc dng lu thng multicast l mt vn phc t p, v cca ch

    multicast cn c nhn bit nh l a ch ca phin truyn d liu c bit, ch

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    khng n thun ch l mt a im vt l cn gi d liu n. Mt sk thut m i c pht trin gii quyt c hiu qu vn nh tuyn dng lu thngmulticast. Do con smy thu trong mt phin multicast l n, nn ngun pht khng cnthit phi bit r tt ccc a ch ny. Thay vo cc b nh tuyn mng cn phic khnng chuyn cca ch multicast vo tronga ch chnh (host addresses). trnh l p li cc hot ng ny, mt thit b nh tuyn duy nht c chn lm b nh tuyn chnh (designated router) cho mi mng, v tthit b nh tuyn chnh nysto ra mt cu trc m r ng hnh cy k t ni tt ccc thnh vin ca mt nhm IPMulticast

    Multcast Router1 Multcast Router1

    (a) : Mng con subnet (b) : Cu trc hnh cy m r ng bt ngun tMR1

    Hnh 9 : Cu trc hnh cy m r ng trong IP Multicast

    Mt cu trc m r ng dng cy ch c k t ni v i phm vi va sao cho ch

    c mt ng k t ni duy nht gia tng c p router.Tu theo tnh hnh mt phn b cc my thu trn mng, truyn thng IP

    Multicast sdng mt trong hai giao thc (v thut ton)nh tuyn sau :

    Giao thc nh tuyn mt cao (Dense-mode routing protocol) : c sdngkhi cc thnh vin nhm Multicast c phn bdy c trn ton mng. Nto ra s lu thng trn ng p trn mng trong tng giai on cc d liumulticasttrin khai v duy tr cu trc hnh cy m r ng.

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    Giao thc nh tuyn mt th p (Sparse-mode routing protocol) : c s dng khi cc thnh vin nhm multicast phn b tha th t trn mng, cn s dng cc k thut chn lc h n t chc v duy tr cu trc multicast dngcy. Trong tr ng h p ny nu lu thng trn ng p cc d liu multicast trnmng sgy lng ph bng thng v c thgy ra nhng vn nghim tr ngtrong vn hnh mng.

    `

    Router Video Server

    Router

    Switch

    Client

    1 5

    3

    3

    2

    Video Stream

    Multicast Router

    4

    Hnh 10 :ng nh p v nhn dng video qua Internet

    Nhn chung, d ph ng thc truyn thng IP Multicast cho php phn phid liu tmt n nhiu im hiu quh n IP Unicast r t nhiu, nhng vn tn timt svn cha gii quyt c nh:

    Cc b nh tuyn trung gian cn phi c khnng Multicast

    Tnh nng v vn cu hnh li (reconfiguration) cc t ng la trong ccmng con

    Vn tin cy v khnng kim sot li trong truyn d liu

    Cc yu cu lin quann cc my thu, cn c card mng v phn mm c bit htr IP Multicast

    3.2.3 Truyn thng IP Simulcast

    3.2.3.1 Nguyn l truyn thng IP Simulcast

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    IP Simulcast l mt gii php m i truyn d liu trn Internet tmt my

    pht sender ng th i n nhiu my thu. N c nhng u im c bn so v i IPUnicast v IP Multicast, gii quyt c nhng hn chca IP Multicast. IP Simulcastsdng m hnh truyn thng m i, gi l m hnh my ch- pht li (repeater-server model). Trong m hnh ny, my ch server squn l v kim sot s k t ni lnnhau gia cc my pht repeaters. V i k thut ny my ch server ging nhmtmy ch server thng th ng, nhng cc my pht li repeater (my thu) c b xung thm tnh nng ca my chngoi nhng tnh nng my khch thng th ng.iu ny c ngh a l mi my thu khng ch hin th dng d liu cho ng i xem, m

    cn truyn pht li dng dliu n hai my khch client khcng sau n.

    `

    `

    `

    ``

    ``

    ``

    `` ` ``

    My ch

    My trm 7 My trm 8 My trm 9 My trm 11My trm 10

    My trm 1 My trm 2

    My trm 3

    My tr m 12 My trm 13

    My tr m 4 My trm 6My trm 5

    My trm 14

    Hnh 11: Thp truyn thng IP Simulcast

    So v i IP Multicast, IP Simulcast gip lm gim b t s server (my phtsender) cn thit bng vic phn ti cho mi my thu receiver (khch hng). Mi mythu tr thnh mt my pht li repeater, truyn i ti p ni dung m n nhn c n

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    hai my thu pha sau (child receiver), to thnh mt m hnh truyn thng hnh thp(Broadcast pyramid).

    Ph ng php ny s lm gim mt cchng k bng thng server cn thittrn mng, do my ch server ch cn gi mt bn copy d liu, sau d liu li c copy li v chuyn ti p b i my thung ngay sau n. Do khng cn cc chi ph phc v dch v d phng m bo bng thng c nh cho cc my thu (trongtr ng h p ny cng ng th i l my pht), nn chi ph cho truyn thng IPSimulcast th p h n trong tr ng h p IP Multicast. H n na IP Simulcast cng khngyu cu thm bt c thit bmng c bit no (nhcc b nh tuyn Router)trinkhai cc dch vtruyn thng nhtrong IP Multicast.

    Smy thu trong thp truyn thng tng theo biu hnh cy nh phn, nuthp c 1 tng th c 2 khch hng, nu c 2 tng th sc 6 khch hng v nu c ntng th sc 2n(n-1)+2 khch hng. Cc my thu/pht li (repeater/receiver) thc hincc chc nng my tr m thng th ng, bao gm sa li v pht hin mt k t ni. IPSimulcast cho php thc hin vic truyn pht cc gi d liu c m bo. y l kh nng m k thut IP Multicast khng th png c v do vy cc dch vsdngk thut ny kh c khnng sa li. Cc gi tin bmt sb bqua, hay cn bsung

    bng thng server thc hin cc yu cu sa li. iu ny lm chi ph bng thngserver tng cao. Nhvy, c ththy im c bit ca truyn thng IP Simulcast nmtrong mi quan hgia cc chc nng server, my pht li v my khch. Cc chcnng ny c thc hin hon ton trn cc thit b u cui (my ch server, mykhch client) v khng ph thuc vo khnng ca cc thit b mng Internet, trong cc server ch thc hin hai chc nng c bn l :

    Truyn pht dng truyn thng

    To cc k t ni, cc lin k t lm nhim vpht li/my thu (repeater/receivers)v duy tr truyn thng IP Simulcast

    Cc my khch lm nhim vpht li bao gm hai modul chc nng :

    Modul pht chuyn ti p (Repeater-client) thu nhn dng dliu truyn thng v pht li mt cch t ng tc dng d liu ny cho my khch clientng sau n. Ngoi ra, n cn thc hin cc chc nng my khch client truyn thng baogm : k t ni, thu nhn d liu, qun l bnh trung gian buffer, gii nn cc

    dliu, sa li, hin th v pht hin tn tht k t ni.

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    Modul pht sa li (Repeater-sender) pht li (rebroadcast) d liu png yucu sa li t cc my khch m n nhn c. N cng thc hin chc nng phti cc yu cu sa li trong cc ch ng trnh m n thu c.

    3.2.3.2 Ph ng th c hot ng truyn thng IP Simulcast

    Trong thp truyn thng IP Simulcast, m bo d liu truyn i c thunhn mt cchy v chnh xc, cc yu cu truyn pht li gi d liu tht lc hay b li c thc hin thng qua cc ng cung c p phsecondary feeds (cc ng

    chm chm trn hnh 12)

    ` ```

    ``

    My ch

    My trm repeater My trm repeater

    My trm repeater My trm repeater My trm repeaterMy trm repeater

    Hnh 12 : M i quan h my ch -my pht l i. Yu c u truyn li cc gi d liu phcvsa li c thc hin thng qua cc ng cung c p ph

    Trong thp truy n thng, my ch server c cc ch c nng sau :

    Sho ch ng trnh ngu n : mt ch ng trnh ngu n th ng bao g m caudiov video t ng t. Cc ch ng trnh ny c sho v chuy n thnh cc dngd liu theo trnh t th i gian.

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    ng bcc ngun d liu ch ng trnh c sho, cc dng d liu theotrnh t th i gian c th n tcc ngun khc nhau : sho cc ngun t ngt, d liu c nn v lu trong a, d liu stcc ch ng trnhang pht,cc ch ng trnh bn quyn hay tcc ngun khc. Cc ch ng trnh ngun cth c x l, c ng bkhc v i ccon ch ng trnh qung co, l p k hoch pht sngNhng ngun khc nhau ca cc dng d liu s cn phi c ng bv nh du th i gianpht li sau ny.

    Nn ngun : mi dng d liu ngun d i dng s th i gian thc c th cnngim kch th c v th i gian truyn pht.y l qu trnh cn bng gianhiu yu tbao gm t snn, cht l ng thu,phc t p nn v gii nn, kh

    nng thch nghi tu theo cc c p bng thng mng sn c, chng nhiu. T p h p (tr n) cc ch ng trnh ngun c nn vo cc gi d liu truyn

    pht. Truyn pht sdng giao thc IP l cng nghtruyn pht trn c s k thut gi d liu. D liu s c t p h p vng gi vo cc gi IPtruyn pht. Cc d liu nn c thhin bng nhiu s ng gi khc nhau thch nghi v i cc tc truyn ti khc nhau, cng nh nng lc x l khcnhau ca tng my PC. Cc s ng gi ny li c sdng cung c p

    dng dliu cho cc my khch clientng sau nc thti p tc pht li. Truyn pht cc gi dliu ca ngun ch ng trnh c nn.

    K t ni cc my tr m client c chc nng pht li. Vic xc l p cc ng cungc p ph cho cc my tr m client c yu cu nhn d liu b sung sa li c thc hin nhsau : khi c mt my tr m client gi mt yu cu n server ngh c sa li. Server sch nh mt my tr m client thch h p anghot ng gn nht lm ngun v gi d liu phc vsa li cho my tr m

    c yu cu thng qua ng cung c p ph c thit l p gia hai my ny. K t ni thng tin thng k, server kim sot vic to dng v hubk t ni.

    Nhm modul pht chuyn ti p trong cc my tr m client ca m hnh thp truynthng thc hin cc chc nng :

    Thit l p cc k t ni : khi my tr m client gi mt yu cu k t ni n my ch,my chsthit l p mt k t ni ring cho my tr m ny.

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    K t ni li : khi mt k t ni b gin on, my tr m s a ra yu cu v thchin k t ni li theo sch o ca my ch.

    Lu gicc gi d liu : cc gi d liu nhn c cn c phnon v ctgiphc vcho vic xcnh cc gi dliu b tht lc.

    a ra cc yu cu pht li sa li : cc yu cu ny c gi n my ch thit l p ng cung c p phphc vcho vic truyn pht li cc gi dliu b tht lc.

    Khc phc s c: trong tr ng h p mt gi d liu b hng khng th sa c, my tram client cn thc hin mt s ng tc tnh thnh: hin th

    tr ng (play silence), pht li hnhnh c, gim c p cht l ng... Gii nn dng dliu nhn c.

    Hin th dng dliu c gii nn cho khn gixem ch ng trnh.

    ng b v i my ch : tc hin th trn my tr m cn c lm ng b (ph h p) v i tc thu pht ca my chhay my tr m ng tr c lm nhimvpht chuyn ti p trnh hin t ng qu ti bng thng mng hay s tr ngr ng ca bnh m trong my tr m. Cc my tr m cn c khnng thch nghiv i nhng sai khc nhvtc truyn pht thuc phm vi cho php.

    Modul pht li phc vsa li trong my tr m thuc m hnh trn thc hin ccchc nng :

    Truyn pht cc gi d liu c nn truyn tngun, chai ng cung c pchnh v ph u c h tr b i chc nng ny, mi ng u c khnngnhn v truyn pht li nh chc nng ny ca my tr m thu nhn dng d liuny.

    Truyn pht li cc gi d liu b li cho cc my tr m ng sau thng qua ng cung c p ph

    Dng truyn thng c phn chia thnh cc dng nh v c truyn phtln l t thng qua cc modul pht chuyn ti p trong cc my tr m c b tr theo s

    dng cy nh phn (hai nhnh). Cc dng chia nhny s c k t h p li trong

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    mt dng duy nht ti mt modul pht chuyn ti p no, gi l superposition ca cynh phn ny. Chui cc superposition trong ton hthng sto thnh mt ng tr ctruyn thng duy nht c tr ng cho qu trnh truyn pht d liu trong ton hthng.V tr ca cc superposition s c chn sao cho ng tr c truyn thng schiau( mc c th) cc tng (stages) ca cu trc hnh cy thnh hai na bng nhau.Cch b tr cc superposition ny s m bo r ng khng modul repeater no khngnhn c d liu ngay ckhi c mt modul repeater cung c p d liu ng tr c n b hng.

    Trong qu trnh thu nhn d liu, cc modul chuyn ti p st p h p cc gi d liu trong mt bnh m buffer, bnh m c sdng b tr cc gi d liu.

    Sau khi cc hin t ng tr bao gm tr Error Delay v Jitter Delay (tr li v tr giaong) c khc phc, cc gi dliu nhn c s c truyn pht ti p tc n tngti p theo.

    Chc nng sa li trong truyn thng IP Simulcast bao gm 2 qu trnh khcnhau : sa li v truyn li d liu phc vsa li. Trn hnh 13 l s phn bth igian cc gi d liu lu li trong vngm sa li v ti p tc truyn i trong ccmodul truyn pht repeaters.

    Cc gi d liuthu nhn c

    Cc gi d liu hinth

    B nh m hin th

    Hin th

    Giai onJitter Giai

    on s a li

    Cc gi d liu c chuy n i

    Giai on pht chuy n tip

    Giai onJitter + tr

    truy n sng Hnh 13 : Th i gian cc gi dliu lu li trong bnh m sa li v pht li

    D liu hin th cho ng i xem c chuyn sang b nh m hin th (playback buffer) v qu trnh hin th c ng bv i tc thu nhn cc gi d

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    liu trnh vic qu ti hay thiu bnh m hin th. Khi mt repeater (my tr mclient) no yu cu k t ni n my chqun tr (server administrator)xin thamgia vo hthng ang truyn thng. Server administrator nhn bit yu cu v s p x prepeater ny vo th tk t ni v yu cu cc my tr m client trong tng ng tr cn cung c p dliu cho repeater ny.

    Khi mt my tr m client mun ra khi h thng truyn thng na ra yucu k t thc k t ni cho my chqun tr . Nu dy cc repeater ch i k t ni khngl r ng, mt repeater s c la chn tdy ny, v thng bo vs thayi s cmy ch a ra cho my b (m) ca my tr m k t thc k t ni. Nu khng crepeater no ch i k t ni, my tr m client hot ng lu nht tng ti p s c

    la chn thay th. Cc schng hc ca cc my tr m client trong hthng truynthng s c thng bo vcho my chqun tr nh cc my tr m conng ngaysau n.

    3.2.3.3m bo cht l ng dch vs dng truyn dn IP Simulcast

    m bo cht l ng dch vtrong truyn dn IP Simulcast cn c : Gim hiu ng tr dao ng Jitter Delay (thnh phn th i gian tr thay i)

    gim qu trnh b tr Jitter Buffering, qua gim thiu l n cn thit ca b nh m trong cc modul nhn/pht chuyn ti p cng nh th i gian tr truyn pht trn mng.

    Gim thiu sl ng gi d liu b tn tht.

    Githit r ng dng d liu lu thng c truyn n tt ccc nt ca cu trctruyn thng hnh cy nh phn. Cc gi d liu ging nhau vkch th c v th i giantruyn cn thit trn mng t. Tc truyn l p gi d liu trn mt giy (p/s). Th igian truyn tmt nt bt k n nt k ti p c gi tr trung bnh l T v gi tr nynhnhaui v i mi c p nt. Th i giann thc tca gi d liu JT (JT T). Tcd liu c truyn n ch (s l ng cc gi d liu i n ch trong mt giy)khi stun theo quy lut phn bPoisson

    p = 1/T

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    Hm phn b(mt ) xc sut JT c th c tnh nhsau :

    f T(t) = pe-pt

    Xc sut th i gian truyn nm trong khong (to , t1) khi l :

    P [t0 < t < t1] = T - T + dt peT T

    T T

    t

    t

    pt +

    +

    1

    0

    Li truyn pht c tnh trn c s sl ng cc gi dliu b tht lc pd sinhra trong th i gian 1 giy ti mt chu k truyn pht ngu nhin no, cng tun theo

    quy lut phn br i r c Poisson pd = 1/T

    Hm mt xc xut (ngu nhin) xut hin li truyn pht khi c dng :

    f E (t) =t p

    d d e p

    3.2.3.3.1 Qu trnh b trJitter (Jitter Buffering)

    Qu trnh b tr Jitter trong b m Jitter Buffering c sdng lm hiung tr dao ng (th i gian tr thay i). Cc b m Jitter Buffer cn c chn l n m bo r ng qu th i gian ch i nht nh, chc chn khng cn gi tin no c chuyn n na v nhng gi d liu cn thiu chc chn b tht lc, khng phi do hin t ng tr thng th ng. Mc xcnh tr mong mun P[t < I] tc l s l ng gi d liu P c khong th i gian ti n nt k ti p khng v t qu khong

    th i gian cn i trong bnh m Jitter Buffer I (ngh a l sau khong th i gian I gid liu no cha t n nt nhn k ti p th chc chn r ng gi tin b tht lc doli) :

    P[t < I] = dt pe pt 1

    0

    T c :

    I = -Tln(1- P[t < I]) = 1- e-pt

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    Tr Jitter cng tng khi cc gi d liu c truyn xung cc tng d i hnhthp. Mt hnh thp v i N nt sc n = log2(N) tng, v hm phn bmt xc xutcho tr Jitter ti tng thn sl :

    f Jn(t) = npe-npt

    Nu th i gian b tr Jitter cn thit ti tng th n l In, tng th i gian b tr Jitter I cn thit truyn nhn c P gi d liu i n tng cui trong cu trc hnhcy nh phn n tng (tc s l ng cc gi tin c th i giann t < In ti mi tng - vittt P[t < In] ) l :

    I = -Tln(1- P[t < In])Kch th c cn thit ca b m Jitter Buffer (th i gian b tr I) tng tuyn

    tnh v i chiu su ca cu trc hnh cy, nh c thhin trn hnh

    Tr Jitter khnguc cng dn

    sau mi tng

    1 2 3 4 nS tng N

    K c h t h u

    c

    b n

    h I

    Tr Jitter u ccng dn qua

    cc tng

    Hnh 14 : Kch th c bnh m Jitter Buffer l mt hm ca stng trong cu trc

    hnh cy

    Githit r ng s truyn pht cc gi d liu n tng k ti p c thc hinsau khi qu trnhm Jitter hon thnh tng truyn pht ti p, ngh a l thnh phntr Jitter c loi b ti mi tng nh b m tr (Buffered delay) trong qu trnh pht chuyn ti p. Nu mc xcnh tr Jitter mong mun ti tng thn l C :

    C = P[t < I]n = (1 e-pt)n

    Th gii ph ng trnh trn tm I ta sc :

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    I = -Tln(1- n C )

    R rng trong tr ng h p ny th i gian m buffering (tc kch th c b

    m) cn thit ch tng nhtheo chiu su cc tng ca cu trc dng cy, nh cthhin trn hnh 14.

    3.2.3.3.2 Qu trnh b trs a li Retry Buffering

    B tr sa li c a vo nhm gim thiu s l ng gi d liu b tn tht.Cc gi d liu b tht lc s c khi phc li sau khi modul thu gi n cho modultruyn pht tng tr c yu cu truyn pht li (retry commands) thng qua cc ng cung c p phsecondary feeds. Hot ng ny c thc hin sau giaion btr Jitter Buffer, v vic gi cc gi d liu b tht lc c nhn li sau mt khongth i gian truyn pht khhi cng v i th i gian b tr Jitter. Qu trnh ny c l pli chon khit c chnh xc truyn pht d liu mong mun. Giskhongth i gian tr sa li trong bnh m mong mun l B, mc xcnh tr mong munP[t < nB] trong thp truyn thng n tng sl :

    P[t < nB] = = 1 n B

    t E dt e E

    0

    nB E e

    Gii ph ng trnhi v i n ta c :

    n = - ln(1 - P[t < nB])/EBChng ta c thk t lun r ng cc li truyn pht tch lu ti mi tng ca thp

    truyn thng, nhng s tch lu ti mi tng li phthuc thc p (second- order) votng tr c .

    Xc xut mt gi d liu khng c nhn ti tng u tin sau m ln phtli sa li (retry period) l :

    P[t < T] =

    m T

    t E

    T t

    E dt edt e E E 2 0

    2

    0

    2

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    Trong cng thc trn h s 2 c a vo tnh cc li trong qu trnhtruyn pht yu cu sa li (retry request). Xc xut mt gi d liu khng nhn c ti tng thn khi l :

    P[t < T] =

    +

    +m T

    t n E

    T t n

    E dt endt en E E 2 0

    )1(

    0

    )1(

    = [ ][ ] [ mT nmT nT n E E E eee + 111 1)1( ]

    Gii ph ng trnh v i nghim m ta c :

    [ ])1ln(

    ),ln(T n E e

    T t P m

    =

    Hnh v sau thhin t ltht lc ca cc gi d liu l m t hm s ca s tng trong

    thp truy n thng IP Simulcast v i s ln pht l i sa li khc nhau t (0 n 4). T l tht lc gi d liu hthng trong th nghi m l 25%, c ngh a l ti tng u tin 75%gi d liu s c nhn chnh xc v 25% s b tht lc do cc l i truyn pht.

    0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16S tng

    T l

    t h

    t l c

    0

    0 . 2

    0 . 4

    0 . 6

    0 . 8

    1

    Hnh 15 : T lgi d liu b tht lc l m t hm s ca stng trong thp truy n

    thng

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    Nh trn hnh, khi l p li sa li nhiu ln, s t c chnh xc kh cao,v trong tr ng h p l p li 4 ln th t lgi d liu b tht lc ti cc tng su trongthp truyn thng tng r t chm.

    3.2.3.3.3 u, nh c im ca truyn thng IP Simulcast trn mng Internet

    So v i cc gii php truyn thng trn mng Internet phbin hin nay nh IPUnicast v IP Multicast, gii php IP Simulcast cho mt s u im h n hn nh:

    Chi phu t th p h n nhiu so v i cc gii php khc do khng c yu cuc bit lin quann cc my chserver, thit bmng ni ring v htng k thut mng ni chung.

    linh hot hthng tt h n, cho php xy dng mt gii php mng tng th v i khnng nng c p v m r ng hthng trong mt th i gian di. Khnngtruyn thng ca IP Simulcast khng phthuc nhiu vo gii php vt l, mitr ng truyn thng, nhiu k t ni, hay nh cung c p dch vmng

    Cht l ng dch vkh cao : chon nay IP Simulcast l gii php duy nht c thit k truyn thng video tr c tuyn trong mi tr ng Internet, cho php sa li v kim sot cht l ng thu ngay trong qu trnh hot ng th igian thc m khng cn thm bt c chi ph b sung bng thng no.y liu m nhng gii php truyn thng video th i gian thc trn mng phbinhin nay khngpng c.

    Hn chduy nht ca IP Simulcast l yu cu t ng i cao vcu hnh mytr m (ti thiu l bx l Pentium III, Ram 256 Mb, Hard disk 20 GB). Tuy

    nhin v i spht trin ca cng nghi p phn cng hin nay cu hnh nay khngl vn kh gii quyt (cd i gckinh tv k thut).

    Tm li, IP Simulcast l k thut tin tin hin nay truyn thng d liuth i gian thc trn Internet. Gii php ny cho phpa tin mt cch nhanh chng, chiu qucc skin l n trn mng Internet m khng cn chi phu tbxung choserver v bng thng mng. Con s cc my tr m k t ni Internet c phc vb idch v truyn thng IP Simulcast hu nh khng b hn ch. Cng v i cc k thut

    nn video tin tin nhMPEG-4, IP Simulcastang ha hn scung c p mt gii

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    Kho lun tt nghi p Gii php truyn tn hiu truyn hnh trn mng===================================================================

    php h p dn cho ccng dng truyn thng video th i gian thc trn mng Internetv nhiung dng khc trn phm vi ton thgi i.

    3.2.4 Mt sgiao th c, ngn ng v chun k thut s dng trong truyn thnga ph ng tin trn mng Internet

    Giao thc l mt t p cc tiu chun trao i thng tin gia hai h thngmy tnh v i nhau, cc chun ny c sdng v chi phi qu trnh truyn thng trnmng. Tt ccc my tnh c lin quann mt qu trnh truyn thngu phi c

    ci t v tun thcng nhng tiu chun nhnhautrnh sai li.Internet l mt t p h p cc mng my tnh c ni k t v truyn thng v i

    nhau trn c s giao thc chung TCP/IP. Cc ch ng trnh truyn hnh tr c tuyn trnmng Internet shin th cho ng i xem trn nhng my tnh v cc thit b hin th khc nhau, c ni Internet qua cc mng con khc nhau. V vy cc giao thc vchun k thut s dng cho truyn thng truyn hnh tr c tuyn cn phi c ch pnhn v c khnng truyn thng trn tt ccc thit b v mng ny. Mt s giao

    thc v chun k thut ang c s dng ph bin trong truyn hnh tr c tuynInternet l :

    3.2.4.1 Giao th c dnh ring ti nguyn mng RSVP (Resource ReservationProtocol)

    RSVP l giao thc dnh ring ti nguyn trn mng Internet, c pht trin b i t chc tiu chun mng quc t IETF (Internet Engineering Task Force) nhmnng cao cht l ng cc dch vtruyn thng trn htng Internet hin ti. RSVP cho php truyn pht d liu trn mng theo mt trnh t th i gian chnh xc (th i gianthc) trn c s duy tr mt quan hth i gian v i ng hchclock, xcnh dung saicho php ca tc bit (bit rate),tr (Jitter) v t lli bit BER. RSVP c khnngyu cu cc thit b nh tuyn Router dnh ring bng thng nht nh cho cc lunglu thngc bit (truyn hnh tr c tuyn ) gia cc mng k t ni, qua xcnhtr c vm bo cht l ng ti thiu ca dch vv to iu kin sdng bng thng

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    mt cch hiu qunht. y liu khng ththc hin c i v i giao thc mngInternet thng th ng TCP/IP.

    Vthc cht, RSVP ch hot ng theo nguyn tc iu khin v pht tn hiuchkhng tr c ti p nh tuyn : khi bt u mt dch vtruyn thng my ch(ngund liu) s a ra mt lnh Path tcc Router ny qua cc Router khc (c tnh nngh tr giao thc RSVP)t i mt hay nhiu a ch ch. Lnh Path bao gm mtnh danh lung xcnh phin ni k t RSVP,a ra yu cu vloi lung d liu vr ng bng thng cn thit. Nu mt b nh tuyn dc trn l trnh i qua khngp ng c yu cu, n sphi tm kim l trnh khc cho lnh Pathi qua. Khilnh Pathi qua, nu Router ng ra nh p phin ni k t, chng snh p v thi hnh

    cc yu cu cha trong lnh Path ny, sau gi tr vmy chmt lnh Resv theotuyn ng c.trnh vic ng i dng chim ot bng thng cho ring h, cnci t cc chc nng kim sot bng thng v quyn u tin m ng i dng c trnmng. Cc Router nh tuyn skim tra tnh tr ng bng thng v quyn u tin nykhi c mt lnh Path c gi n. Vic dnh ring ti nguyn trn mng Internet phitr chi ph bxung b i nh cung c p dch vInternet.

    3.2.4.2 Giao th c truyn ti th i gian th c RTP (Real-time Transport Protocol)v giao th c kim sot th i gian th c RTCP (Real-time Control Protocol)

    Internet l mng truyn thng khngm bo, tc l khng chc chn 100%gi d liu sgi n ch. RTP l mt giao thc to khnng ng b v sa linhm khc phc vn tn tht v tr d liu. RTP cng xcnh mt nh dng chovic m ho audio v videothc y s lin lc gia cc nn chun my tnh, cc

    hthng vn hnh, cc sn phm phn mm ng dng khc nhau. Nh cc tr ng d liu c bit c ng du th i gian v c cha cc thng tin vtrnh tphnond liu, cc my tnh thu d liu c thsdng tr ng nyti to ccc tnh th igian ca dng d liu. Nh qui nh thng nht cch thc truyn d liu a ph ngtin th i gian thc tmy ny sang my khc trn mng nn giao thc truyn ti th igian thc RTP c khnng x l cc dng d liu lin tc, m phng phn b t ngtc, cc ch ng trnhng dng iu khin. Giao thc ny c ng dng kh phbin

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    trong cc dch vnhnhn bit loi thanh ton,nh sth t, nh du th i gian, vgim st vic truyn dliu

    Mt giao thc khc lin quann RTP l giao thc kim sot th i gian thcRTCP. y l giao thc kim sot tr ng thi ca dng truyn thng th i gian thc.Bng vic sdng RTCP, cc bo co thu v pht c truyn i lin tc trong sutth i gian truyn thng sao cho ccng dng giao thc RTP c ththu c cc boco RTCP vvic d liu RTP hin ang c cung c p nh thno. Chai giao thctrn c a ra b i IETF.

    3.2.4.3 Giao th c truyn a dng tin cy cao RMP (Reliable Multicast Protocols)

    c thit k b i IETF nhm m bo scung c p s ton vn 100% d liutrn mt mng khi cn thit. Khi truyn cc ch ng trnh truyn hnh hay video, do nhy ca mt ng i v tai con ng i c gi i hn, nn chng ta khng cn s truynhon ho d liu v c thbqua nhng tn tht nhkhng quan tr ng, cng nh s can nhiu trong cc hnhnh v m thanh. Nhng truyn cc c s d liu chun

    hay cc phn mm, th khng c php c bt k tn tht d liu no. Trong tr ngh p cn sdng giao thc truyn a dng tin cy cao RMP trong truyn thng trnmng Internet.

    3.2.4.4 Ngn ng nh du m rng XML (Extansible Markup Language)

    XML lnh dng file d i dng textc c, c W3C pht trin tngnngHTML (Hypertext Markup Language). XML c thit k thc hin lu tr , pht hnh d liu trn cc Website mt cch ddng v linh hot h n nhiu so v iHTML, cho php ng i thit k Web nh ngh a r ni dung ca dliu bng cch toui m r ng theo mnh. XML cho php s dng ngn ng nh du tng qutchun SGML (Standard Generalized Markup Language) trn web, v cho php xcnh, nhn dng v s dng cu trc, loi v ni dung ti liu. XML c thch nhcho tng thit b u cui thhin hay khng thhin ni dung, hay ch thhin phnno ca ni dung, n thm ch c thtrnh by ni dung trong mi tr ng truyn

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    thng khc (nhaudio thay cho text) v htr k t ni cc c s dliu, truyn v hinth cc thng tin / thng bo d i dng vn bn text tr c ti p.

    Trongng dng truyn hnh Internet, s phn tch v x l cc file XML cthbt u ngay khi cc phn u tin c thu b i my thu thay cho vic phi in lc thu c y file c phti. Sphn tch c php ca cu trc file XML c thc hin song song ngay l p tc trong sut qu trnh thu. Cc thng tin c tora kim sotng dng bn ngoi. Nh vy vic lu tr tc th mt file XMLnguyn thl khng cn thit v shin th c thbt u ngay l p tc.

    3.2.4.5 Ngn ng tch h p truyn thng a ph ng tin ng b SMIL(Synchronized Multimedia Integration Language)

    SMIL l k t quca Dn truyn thnga ph ng tin ng b nhm thitl p chun k thut c khnng ng bcc truyn thng d liu khc nhau (nh text,ho, audio, video) sao cho vic hin th ni dung truyn thng c thc hintheo mt ph ng thc k t h p, m bo tnh nng a truyn thng. D n c thc

    hin b i th p cng nghi p quc tW3C (World Wide Web Consortium). SMIL ckhnng tr n ghp cc d liu truyn thng trong ccnh dng khc nhau, nh vyc th tch h p cc truyn thng trong cng mt frame vng b chng trong mtch ng trnh. Khnng ny to thun l i cho cc nh thit k web thit k v bxungcc ch ng trnh truyn thng khc nhau ln cng mt Website. SMIL c xy dngtrn c s ngn ngXML.

    3.2.4.6 Giao th c dng d liu th i gian th c RTSP (Real-Time StreamingProtocol)

    RTSP l giao thc mc ng dng kim sot vic cung c p v lu tr nidung ca cc d liu c c tnh th i gian thc trn Internet v Intranet, RTSP c pht trin b i Real Networks, Netscape, Columbia University v c IETF chunho. RTSP c th truyn m thanh v hnhnh tr c ti p hay c thu t tr c. Cho

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    php t ng tc hai chiu h tr cho IP Multicast v i chi ph truyn thng th p, anton caoRTSP hin ang c trn cc nn my tnh phbin hin nay.

    3.2.4.7nh dng dng tin tin ASF (Advanced Streaming Format)

    ASF do Microsoft to ra xc nh nh dng lu tr i v i cc truynthng theo dng (streaming media). ASF lnh dng file chun m trong ni dungmultimedia s c lu tr , to dng v hin th nh cc cng c, cc my chserver,v cc my tr m ca nh cung c p truyn thnga ph ng tin trong cng file chung,

    thay cho vic phi sdng cc file video,ho, text v audio ring bit.

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    CH NG 4 : CC GII PHP CUNG CP CH NG TRNH VTV QUAMNG INTERNET

    --------&&--------

    4.1 Xu thv nh ng iu kin pht trin truyn hnh Internet

    Trong th i gian gn y, nh nhng ci thin ng k vc s h tng vcng ngh truyn dn Internet, nh s hon thin khng ngng ca k thut nn vtrnh din video trn mi tr ng mng. Truyn hnh Internet (Television Webcasting) c nhng b c tin ng k v ang dn tr thnh mt ngnh cng nghi p gii tr,tuy tc pht trin vn cn mc khim tn h n so v i cc dch vmng khc nh Radio Internet. Cc nghin cu v truyn hnh v Internet cho thy, hu ht cchng truyn hnh l n trn thgi i u thit l p s hin din ca mnh trn mitr ng mng thit l p cc mi lin hkhch hng v thu th p tin tc tkhn gi.L i nhun m cc hng thu c t cc dch v trn mng Internet l 76% t qungco, 24% tbn cc ni dung ch ng trnh v 19% t th ng mi in t. L i dng

    u th ca mnh trong l nh vc truyn hnh, cc hng truyn hnh l n nh CNN,MSNBC v CBS News hin ang l nhng ng i ni ting nht trong l nh vc truyn pht qung b cc ch ng trnh truyn hnh trn Internet.

    Cc yu t quan tr ng thcy s pht trin ca ngnh cng nghi p ny lmi tr ng php lut minh bch, tdo -c bit l lut vbn quyn, spht trin cahtng k thut Internet bng r ng v cng nghnn video. Nhn chung trn thgi ihin nay, truyn hnh Internet vn ang l mt ngnh cng nghi p trong giaiontr ng n c, ang b c nhng b c u tin trn con ng chinh phc khn gi.V i l i thsn c vni dung l cc ch ng trnh truyn hnh, trn c s cc timnng to l n bt ngun tkhnng :

    Cho php ng i dng t ng tc, traoi thng tin v i nhau trn phm vi toncu, tc th i v dsdng.

    Khnng qun l tng ng i sdng thng quaa ch IP (ging nhcc ach c tr c ng k theo s nh) thit l p nn mt th tr ng dich v truyn hnh gii tr trong mt thgi i o r ng l n.

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    Mi tr ng truyn dn Internet bng r ng c mt sc h p dn r t l n i v i

    cc hng truyn hnh. D i sc p ca nhu cu lm tng gi tr gia tng cc ch ngtrnh truyn hnh v tng ngun thu, d mun hay khng th cc hng truyn hnhusphi gia nh p thgi i huyn o ny v vic truyn pht ch ng trnh truyn hnhtrn mng Interneti v i bt k mt hng truyn hnh no ch cn l vn th i gian.Theo nghin cu ca MRG (Multimedia Research Group, Inc) cng b cui nm2003, loi hnh IP video xem c trn Tivi, Set top box v PC schim mt th phn l n trong cc dch vgii tr ni mng ti nh v i s thu bao tng 4 ln trn phm vi ton thgi i, t d i 2 triu thu bao nm 2004 sln n trn 8 triu vo

    nm 2006, v doanh thu t cc dch v ny s tng t 1 tUSD lnn 6 tUSDtrong cng mt th i gian.

    y cng l mt c hi tt cc hng truyn hnh pht trin dch v truynhnh Internet ca mnh.

    So v i truyn hnh truyn thng, truyn hnh Internet cng c mt s u im sau:

    Ph h p vth i gian va l :y lu thtuyt i so v i cc ch ng trnhtruyn hnh thng th ng. Cc my chc th c t gi sao cho ph h pv i mi gi ca tng vngng i xem d u cng c thxem ch ngtrnh vo th i im thch h p v i h.

    Khnng la chn cc chuyn mc u thch :y cng l mt im mnh mmt knh truyn hnh thng th ng kh c khnng png c.

    Ti xung, lu tr v xem li khi cn thit.

    Gi thnh r h n nhiu ln so v i