TNG QUAN V IPTVTrong ni dung bo co ny, chng ta s cp n khi nim v dch v IPTV, gii thiu cu trc, cc phn t mng v cc giao thc truyn ti v bo hiu tham gia vo qu trnh truyn ti dch v IPTV t u cui-ti-u cui.

I. Khi nim IPTVIPTV c gi l truyn hnh trn giao thc Internet, Telco TV hay truyn hnh bng rng, vi ngha truyn ti truyn hnh qung b v/hoc video theo yu cu, chng trnh pht thanh c cht lng cao trn mng bng rng. Theo quan im ca i tng s dng, vic khai thc v xem IPTV cng ging nh dch v TV tr tin. ITU-T (ITU-T FG IPTV) chnh thc chp thun nh ngha IPTV nh sau: IPTV c nh ngha l cc dch v a phng tin nh truyn hnh/video/audio/vn bn/ ha/s liu truyn ti trn cc mng da trn IP c kim sot nhm cung cp mc cht lng dch v, mn nguyn, bo mt v tin cy theo yu cu.[13] T quan im ca nh cung cp dch v, IPTV bao hm qu trnh thu thp, x l, v truyn ti mt cch an ton ni dung video trn h tng mng da trn cng ngh IP. Tham gia vo qu trnh cung cp dch v IPTV gm nhiu nh cung cp dch v t cc nh cung cp dch v truyn hnh cp, truyn hnh v tinh n cc cng ty Vin thng ln v cc nh khai thc mng ring nhiu ni trn th gii. IPTV c mt s c im sau: H tr truyn hnh tng tc - Cc kh nng hot ng hai chiu ca h thng IPTV cho php nh cung cp dch v a ra mt s lng ln cc ng dng truyn hnh tng tc. Cc loi hnh dch v c phn phi qua dch v IPTV c th bao gm truyn hnh trc tip tiu chun, truyn hnh trung thc cao (HDTV), cc tr chi trc tuyn, v kt ni Internet tc cao. Khng ph thuc thi gian - IPTV khi kt hp vi my thu video s cho php to chng trnh ni dung khng ph thuc thi gian bng c ch ghi v lu li ni dung IPTV v sau c th xem li. Tng tnh c nhn - H thng IPTV t u cui - u cui h tr thng tin hai chiu v cho php cc user s dng la chn v thit lp vic xem TV theo s thch ring nh chng trnh v thi gian xem a thch. Yu cu v bng thng thp - Thay v phi truyn ti tt c cc knh cho mi i tng s dng, cng ngh IPTV cho php cc nh cung cp dch v ch cn phi pht cc knh m i tng s dng yu cu. Tnh nng hp dn ny cho php nh khai thc mng tit kim bng thng. Kh nng truy nhp trn nhiu loi thit b - Vic xem ni dung IPTV khng b gii hn l dng cho cc my thu hnh. Cc khc hng thng s dng my tnh c nhn v cc thit b di ng truy cp ti cc dch v IPTV.

Cc dch v IPTVIPTV khng ch n thun l IP video. Trn thc t, cc nh khai thc vin thng ang tp trung vo dch v ny to ra s khc bit ca dch v h cung cp vi cc dch v m cc nh khai thc mng truyn hnh cp hay v tinh cung cp. Tt c cc la chn cu trc v cng ngh c s tp trung vo vic phn phi nhiu loi dch v video theo yu cu v video qung b, nhng vi kinh nghim v cc dch v thoi v s liu tc cao cho php cc nh khai thc vin thng cung cp cho khch hng cc dch v tch hp b xung l mt phn ca gi dch v IPTV ln. Cc dch v chnh thng c trin khai trc l dch v video theo yu cu v video qung b, tuy nhin cc nh khai thc vin thng u c k hoch b xung cc dch v ny vi cc dch v tr chi, qung co, m thanh, thng tiniu cn bit l nh ngha v phm vi ca cc dch v ny s lin tc c tin trin theo thi gian. Bng 2-1 m t tng quan cc loi dch v IPTV khc nhau hin ang c d kin v trin khai [17].

Bng 2-1: V d v cc dch v IPTV.Live TV Digital TV Premium TV Pay-per-view Near video-on-demand Program guide Stored TV Video on demand Subscription VoD Time-shifting PRV Network PVR Cmmunictaion Residental VoIP portal SMS/MMS mesaging Instant messaging Mobile services portal Video conferencing Emergency alert system Entertainment Gaming Gambling Karaoke Internet TV Commerce Telecomerce Targeted/interactive advesting

ASP

Distance learning Home automation portal Converged services Hospitality

1. Cc dch v VideoCc dch v IPTV video c th phn thnh hai nhm: pht qung b v pht theo yu cu. 1) Cc dch v video qung b V c bn, cc dch v video qung b khng khc g so vi cc dch v video m cc nh khai thc truyn hnh cp, v tinh, mt t cung cp ngy nay. iu ny gp phn to thnh tiu chun i vi dch v TV, khng k n cc c ch truyn ti: lai cp

ng/quang, DSL hay FTTxCc knh video qung b bao gm cc knh truyn hnh quc gia, a phng v cc knh tr tin (nh HBO). S cc knh qung b khu vc c th thay i theo th trng, cc knh ny thng h tr cc phin bn theo khu vc ca cc mng gc (ABC, CBS, NBC v Fox..). Mt s trong cc knh qung b c nh dng trung thc cao (HD), iu c ngha cc nh khai thc vin thng c th cung cp cho khch hng c hai loi knh qung b tiu chun (SD) v trung thc cao (HD). Mt phn ni dung qung b c th c lu li trong mng v s dng sau . 2) Cc dch v video lu tr Cc dch v video lu tr c nhiu dng v l nn tng phn bit vi cc ni dung video khc c truyn ti qua cc mng IP. Ni dung video lu tr p ng c nhiu cc s thch khc nhau ca ngi xem. Ty theo v tr lu tr, khch hng c th tn dng c cc u im ca ni dung video lu ti thit b khch hng hoc mng iu khin mt cch linh hot khi s dng dch v nh: tua nhanh, tua ngc, tm dng.. nh khi h s dng VCDs/DVDs. Ni dung video lu tr l ng lc chnh thc y s pht trin phn mm lp dch v trong cc mng IPTV cng nh cc ty chn ca set-top box. Cc ty chn ni dung video lu tr bao gm: VoD lu tr cc b: Ni dung c xem l ph bin rng ri s c pht qung b ti CPE qua mng IP v lu cc b khch hng c th xem theo yu cu. Cc ni dung ny thng gn vi qu trnh xc thc quyn s dng khi xem i vi tng thu bao. VoD lu trn mng: VoD lu trn mng dnh cho cc ni dung c coi l khng ph bin cho nhiu thu bao ti cng thi im. Khch hng c th yu cu xem ni dung ngay lp tc v/hoc sau khi yu cu. Ni dung c th xem ngay c truyn ti di dng unicast trn mng IP, trong khi ni dung xem sau yu cu c tp hp theo nhm cc thu bao v c th truyn ti dng broadcast hay narrowcast da trn th t tng ng i vi cc thu bao khc. iu ny s cho php nh cung cp dch v s dng ti u cc ti nguyn mng mt cch linh hot. VoD thu bao: VoD thu bao l bin th ca hai dch v trn, cho php khc hng quyn xem mt s ni dung c c cho php trc trong mt hong thi gian xc nh, tn dng u im ca c hai ni dung video lu trn mng v cc b. Ghi li ni dung video theo yu cu c nhn: PVR (Personal Video Recorder) cho php ngi dng quyn ghi li cc chng trnh qung b/theo yu cu xem li sau . Cc quyn xem ni dung thay i ty theo vic s dng mt ln, nhiu ln hay khng gii hn ni dung v phn mm qun l bn quyn (DRM) l yu t quan trng trong cc trng hp ny kim sot qu trnh chia s ni dung gia cc thit b trong nh thu bao. Ghi li ni dung video v lu trn mng (Network-based PVR): tng t nh dch v PVR, s khc nhau ch yu l v tr lu ni dung, trong trng hp ny l trn mng, thay v s dng thit b ca khch hng. Dch v ny cho php cc thu bao vi set-top box n gin tn dng c cc u im ca cc dch v video lu tr

v cho php cc nh cung cp dch v tp hp cc ni dung lu tr trong mng mt cch ti u nh gim chi ph so vi vic thu bao phi s dng set-top box phc tp. Dch v ny cng cung cp mt cch tt nht cho thu bao kh nng linh hot trong vic la chn chng trnh v mng c kh nng lu nhiu ni dung hn soa vi set-top box ca khch hng.

2. Cc dch v IPTV audioNu ch c dch v IPTV audio th chc chn khng kch thch cc thu bao chuyn nh cung cp dch v v cng khng nh cung cp dch v u t mt lng ln tin vo h tng mng phn phi dch v IPTV. Tuy nhin, khi kt hp vi cc ty chn khc n s nng cao tnh hp dn ca gi dch v tng th. a) Dch v radio broadcast Dch v ny cho php khch hng d tm bt k i pht no trn th gii v nghe qua li ra m thanh ca TV hay h thng loa km theo. b) Dch v music broadcast Theo quan im dch v m thanh, dch v ny rt ging qung b video c bn, ngha l ngi dng c th s dng nhiu knh m nhc khc nhau. Dch v ny kh ph bin v c cung cp bi nhiu nh cung cp dch v cp/MSO. Dch v m nhc ny thng i km vi thng tin ha v ni dung nhc hin th trn TV ca khch hng. Hng dn chng trnh chn knh cng tng t nh i vi cc knh video. c) Music on demand Tng t nh VoD, quyn yu cu v nghe tng t nh i vi cc dch v VoD. Mi quan h gia cc nh cung cp ni dung v phng tin l yu t quan trng nh i vi dch v VoD m bo c c th vin ln cc file nhc. d) Music subscription service Cho php thu bao lu tr v sp xp theo s thch ca mnh. Dch v m nhc theo yu cu s c truyn ti qua mng IP theo cch tng t nh cc dch v VoD s dng cc c cu broadcast hay unicast, theo thi gian v mc tng ng vi cc thu bao khc.

3. Cc dch v IPTV gamingChi game (mt ngi hay nhiu ngi cng lc) trn truyn hnh l dch v ring bit m cc nh khai thc vin thng ang xc tin tch hp vo cc gi dch v IPTV ca h. S c nhiu loi ch tri cho nhiu loi i tng khc nhau cng nh cc tr chi cho 1 ngi v nhiu ngi chi cng lc. Khch hng c th la chn ngi chi cng cng nh ln k hoch thi gian chi vi ngi khc.

4. Cc dch v thng tin tch hpDch v thng tin IPTV tch hp l lnh vc trong cc nh khai thc vin thng c u th hn so vi cc nh cung cp a dch v/truyn hnh cp. Cc dch v thng tin tch hp s tn dng cc li th v ti nguyn ca cc nh nh cung cp dch v vin thng khi cung cp cc dch v thoi v truy cp Internet tc cao. Cc v d v dch v thoi v Internet tch hp c m t nh sau: a) Dch v thoi tch hp Dch v thoi tch hp cho php cc thu bao s dng TV ca h m rng cc chc nng dch v thoi di ng v c nh. V d:

Dch v thng bo cuc gi n (Incoming Call Notification Service): Hin th biu tng trn TV, thng bo cho thu bao c cuc gi thai/vdieo n. Ngoi ra cn h tr cc chc nng hin th s thu bao v ghi li cuc gi. Dch v thng bo bn tin (Message Notification Service): Hin th biu tng trn TV, thng bo cho thu bao c li nhn (voice mail) trong hp th km theo dch v thoi c nh v/hoc di ng. Dch v thit lp kt ni (Connection Establishment Service): cho php thu bao gi thoi/video t TV ca h. Dch v hi ngh thoi/video (Voice/Video Conferencing Service): cho php thu bao tham gia v/hoc khi to hi ngh thoi/video. Dch v danh b (Directory Service): Cung cp cho thu bao danh b in thoi in t c th truy cp qua TV.

b) Cc dch v Internet tch hp Cc dch v internet tch hp s cho php s dng TV s dng cc ng dng Internet trc y phi s dng bng my tnh c nhn. Cc dch v ny khng nhm thay th cc ng dng Internet da trn PC m chng cung cp cc bin php thun tin hn truy cp thng tin trong nhng khu vc khc nhau trong nh thu bao hay cc thi im khc nhau. Duyt web bng TV (TV web browsing): cho php thu bao xem cc trang web trn TV ca h. Nhn tin bng TV (TV Instant Messaging): cho php thu bao thng tin qua IM trong khi ng thi s dng cc dch v video/audio hay tr chi khc. TV Email: cho php thu bao s dng cc ng dng client trn TV c, gi v nhn th in t. Telecommerce Service: tng t nh cc dch v e-commerce, cc dch v ny c thit k cho php thu bao s dng TV ca mnh tm kim v t mua hng.

5. Cc dch v qung coH tr cc qung co qung b truyn thng v xen vo cng vi qung b cc b ti cc im khc nhau trong mng IPTV. Kh nng tng quan gia cc set-top box v cc mc u tin dch v cho php nh cung cp dch v a ra cc dch v qung co c hng i tng. Vic tch hp cc dch v qung co hng vo i tng s dng vi cc dch v mua bn t xa cho php nh cung cp dch v c th gip khch hng ca mnh thc hin c nhng tha thun mua bn theo yu cu. Vi bn cht hai chiu ca mng thng tin v cc dch v kt hp, cc thu bao c th cung cp kin nh gi ca mnh i vi qung co trn IPTV lm cho dch v qung co ny st vi i tng hn, ph hp hn.

2. Cu trc v cc cng ngh mng IPTV

1. M hnh cu trc mng IPTVITU-T m t m hnh chun dch v IPTV nh trong Hnh 2-1. Trong , vai tr ca bn thnh phn chnh l: Nh cung cp ni dung: s hu hoc c cp php bn ni dung hay quyn s hu ni dung Nh cung cp dch v: cung cp dch v IPTV ti khch hng. Nh cung cp dch v da trn QoS trong cc mng ca nh cung cp mng m bo QoE cc dch v IPTV. Nh cung cp mng: cung cp cc dch v mng cho c khch hng v nh cung cp dch v. Nh cung cp mng cn cam kt khng ch vi nh cung cp dch v cn vi c khch hng v cc tham s mng (v d bng thng, kh dng dch v) Khch hng: s dng v tr tin cho cc dch v IPTV.

Hnh 2-1: M hnh chun IPTV.M hnh hon ton n gin nhng nh ngha n gin ny gip chng ta phn bit hn na cc dch v IPTV khi xem xt tng vai tr. Trn thc t, cc mng video IP l nhng h thng kh phc tp c cu thnh t rt nhiu phn t, l mt trong nhng l do m chng ta kh thit k v pht trin. V bn cht cc mng video IP ca cc nh khai thc vin thng l kh phn b hn so vi cc nh cung cp mng video cp, thng tp trung nhiu chc nng ti trung tm chnh. Hnh 2-2 minh ha mt cu trc mng IPTV tiu biu trn thc t. C th thy, trn mng mng thc t, truyn ti dch v IPTV t u cui-ti-u cui cn c s tham gia ca nhiu phn t mng v hng lot cng ngh. Trong cc phn tip theo, chng ta s tp trung vo cc cng ngh s dng trong lp h tng dch v IPTV, bao gm cc h thng ngun video IP, cc my ch VoD, cc phn mm trung gian (middlleware), cc set-top box v phn mm bo mt/qun l bn quyn l c trng i vi dch v IPTV v mt s giao thc mng lin quan n qu trnh truyn ti ni dung IPTV.

Hnh 2-2: Cu trc mng IPTV. 2. Cc cng ngh nn videoMt phn ln lng video IP c truyn ti trong cc mng IPTV hin ti tn dng u im ca cc tiu chun nn MPEG-2 c t nhng nm 90 trong cc h thng mng truyn hnh cp, v tinh v mt t. Nu s dng MPEG-2 (hay cn gi l H.262) cn bng thng khong 3,75 Mbps truyn tn hiu video tiu chun (SD) trn mng IP, trong khi tn hiu video dng HD yu cu bng thng 12 15 Mbps truyn. Do vy, truyn hai knh TV dng SD ti thu bao cn bng thng khong 8 Mbps. Cc cng ngh nn tin tin hn nh H.246 (cn gi l AVC hay MPEG-4 Part 10) v WM9/VC-1 (cn gi l SMPTE 421M, VC-1 trc y cn gi l VC-9, phin bn tiu chun ca Windows Media 9) c hiu sut nn gp 50% so vi MPEG-2. Bng thng l vn c quan tm khi la chn cng ngh nn s dng cho h thng. Tuy nhin, cn c mt s yu t khc cn phi quan tm. S dng MPEG-2, di GOP, nhm cc nh gia cc khung I khong 12 18. S dng m ha MPEG-4, s cc khung I c th ln ti 300. iu ny khin cho lung video d b nh hng bi mt gi, v cc khung m ha H.246 cha nhiu thng tin hn nn mt cc khung ny gy tc ng ln n cht lng hnh nh v cm nhn ca khch hng. Ngoi cc l do k thut, cn quan tm n cc yu t khc nh kh nng thng mi ha ca cc b m ha ny trong cc set-top box, vn bn quyn v kh nng phi hp hot ng vi cc thnh phn mng khc.

Hnh 2-3: Qu trnh pht trin cc cng ngh nn.

Source: Envivio

Hnh 2-4: Hiu qu s dng cc k thut nn trong mng ADSL.Cc cng ngh MPEG-2 l rt kh dng v chi ph thp, tuy nhin, s lng cc sn phm s dng MPEG-4 ngy cng tng, y s l la chn c u chung trong cc mng video IP th h mi. Hnh 2-3 minh ha qu trnh pht trin ca cc cng ngh nn. Hnh 2-4 minh ha hiu qu v bng thng khi s dng cc cng ngh nn trong mng ADSL. c thm thng tin chi tit v cc cng ngh nn ny, tham kho cc ti liu [3], [21].

3. Cc h thng VHECc h thng head-end video l mt trong cc thnh phn ch cht ca lp h tng dch v IPTV. Do bn cht phn b ca mng cc nh khai thc vin thng, nn d tn ti khi nim ngun video ch hay quc gia th trong cc h thng vn c cc ngun cc b phn b theo khu vc trong cc VHO vi cc chc nng tng t nhng quy m nh hn. Cc ngun video ny thc hin bn chc nng c bn sau: Thu thp ni dung: thu cc ni dung video t cc ngun v tinh v mt t. Lu tr ni dung: lu v thm vo ni dung nh VoD v qung co.

sau:

Chun b ni dung: sa son ni dung v phng din k thut trc khi phn phi. Phn phi ni dung: phn phi ni dung chng trnh trn mng IPTV thc hin cc chc nng chnh ny, cc h thng ngun h tr cc tnh nng M ha video: s dng cc b m ha video nn ni dung video theo dng chun nh MPEG-2 hay MPEG-4 hoc WM9. Cc b m ha cng h tr qu trnh nn m thanh thnh dng tiu chun iu khin tc cc lung video: qu trnh ny iu khin v phn knh cc lung video vi nhiu loi tc thu c t nhiu ngun khc nhau ghp vi nhau trc thng cc lung ring bit vi tc khng i v gim i phn phi trn mng truy nhp. Chuyn i dng m ha: qu trnh ny thay i dng m ha tn hiu video. V d, chuyn i tn hiu video thi gian thc dng MPEG-2 thnh dng MPEG-4 gim kch thc, thun tin hn cho qu trnh lu tr v phn phi trn mng. To gi tin video: qu trnh ny to gi cc khung video MPEG-x thnh cc gi UDP phn phi trn mng IP. Mt s mng hin c c th gi di dng ATM. iu ny dn n vic h tr nhiu loi giao din.

Ngoi cc chc nng c bn trn, cc h thng ngun video cn c thm chc nng chn qung co. Cc h thng ngun video thng l nhng thit b c thit k cho cc trung tm vi cc yu cu v mi trng v kh dng cao. V cc chc nng ngun video c thc hin ti nhiu im trong mng IPTV, nn cc yu cu v thng c th thay i ty theo quy m, loi cc b m/gii m, giao din...

4. Cc my ch VoDCc my ch video chu trch nhim lu tr lu di mt lng ln cc ni dung video s, c th bao gm c cc chng trnh TV qung b. Cc my ch ny c th c phn b trong nhiu ni trn mng IPTV, t trong cc ngun video quc gia ti cc VHO khu vc. Cc my ch VoD c nhiu loi vi dung lng lu tr khc nhau ty thuc vo ni dung v a im lu tr. c trang b ch yu vi cc kt ni Gigabit Ethernet (xu hng tin ti 10 GE) vi cc b m ha, chuyn mch lp 2 v cc b nh tuyn bin lp 3, cc my ch VoD c kh nng cung cp ng thi v n nh qua mng mt lng ln cc lung video di dng unicast hay multicast. Cc tham s cht lng ch yu i vi cc my ch VoD l dung lng lu tr v thng lng v s cc lung video pht ng thi. Cc my ch VoD th h sau hng ti ch tiu 50.000 lung video trn mt modul v t 10 n 12 TByte dung lng lu tr. Hnh 2-5 minh ha xu hng pht trin cht lng cc my ch VoD.

Ngun: Arroyo Video Solutions

Hnh 2-5: Xu hng pht trin cc my ch VoD.Cng nh vi cc phn t khc trong lp h tng dch v IPTV, iu quan trng i vi cc my ch VoD l phi h tr nhiu loi cng ngh nn i vi ni dung video c lu tr. Da trn cc mu lu lng v c tnh thu bao, phn mm my ch VoD cho php phn phi ni dung qua mng mt cch thng minh.

5. IPTV MidlewareMiddleware c coi l h iu hnh IPTV, qua thut ng ny c th thy ti sao Microsoft c u th trong th trng ny. Middleware l b no ca ton b h thng IPTV, do vy y l thnh phn c chc nng then cht trong h tng phn phi video u cui-ti-u cui. Middleware cng xc nh nhiu im tch hp vi tt c cc thnh phn h tng mng. Hnh 2-6 minh ha tng th qu trnh thc thi middleware [23].

Hnh 2-6: Middleware.Khi th trng IPTV mi bt u, cc nh cung cp dch v IPTV thng t vit cc middleware ring ca mnh to ra nn tng phn phi dch v IPTV trn . Mt s nh cung cp thit b hng u tham gia v th trng vi cc h thng m, cung cp

cho cc nh cung cp dch v cc cng ngh v cng c c c im chung xy dng cc dch v video IP, chnh l middleware. Ni chung, phn mm middleware c bn chc nng chnh: H tr khch hng trong vic s dng dch v nh ngha dch v, cc gi dch v v tnh cc Giao tip vi cc h thng ngoi nh cc set-top box, cc my ch VoD v trong mt s trng hp, cc phn t mng bn di. Qun l cc giao dch, cc ngun a phng tin, thu bao v s liu lin quan.

Trong mi lnh vc ny, middleware h tr rt a dng cc tnh nng i vi thu bao v nh khai thc nh m t trong Bng 2-2.

Bng 2-2: Cc tnh nng ca middleware i vi thu bao v nh khai thcSubscriber Features On-screen presentation and user interface Electronic program giude (EPG) Per-service display and interactivity (VoD, DVR, PVR, etc) Intergrated service display and interactivity (TV web browser, caller ID, message notification, TV email, etc) Programming information Programming Remider Parent control Account information Operator Features Robust application programming interface Software development kit (SDK) Auto-configuration of IP set-top box Set-top box tracking and auditing Service management Billing Interface Subscriber management and tracking Subscriber self-ordering/provisioning Transaction management Reporting functions Phisical and content asset management Content asset placement intellegence Security integration Highly scalable software architecture High availability Multi-vendor integration (set-top boxes, VoD servers, etc)

Cui cng, kh nng m rng l yu t quan trng i vi nn middleware, v cc nh khai thc ln trn th gii mun nhm ti s cc thu bao ln n hng triu cho n cui thp k ny, kh m ca nn middleware s l mt trong cc lnh vc chnh pht trin ca cc hng nh Microsft TV, Myrio (nay thuc Siemens), Orca Interative

6. IP set-top boxIP set-top box c vai tr gii m ni dung video, c qung b v VoD. Gi i vi cc set-top box thay i ty thuc vo kh nng chng c cc tnh nng sau hay khng: Dung lng/kh nng lu tr ni dung lu di H tr VoD

H tr ghi video s (DVR) H tr phn gii SD/HD H tr h iu hnh. Kh nng gii m n/nhiu dng MPEG bng phn cng H tr cp nht firmware cho b gii m Qun l iu khin t xa H tr bo mt/DRM

7. Bo mt v quyn truy cpBo mt ni dung l yu cu ct yu khi cc nh khai thc vin thng chuyn hng sang cung cp IPTV, nhng bn cht t nhin ca cc dch v video IP s thay i cc yu cu v bo mt ni dung. Cc tnh nng IPTV nh VoD v DVR s bt buc phi c cc yu cu v bo mt, to ra c hi mi cho cc sn phm bo mt th h sau da trn phn mm. Cc h thng truy cp c iu kin (CA) truyn thng c thit k cho cc mng truyn hnh cp qung b bo mt ni dung ti ngun v m ha ni dung ti thit b nh thu bao. Mc ch ch yu ca cc h thng ny bt buc thu bao phi tr tin cho cc chng trnh h xem v gii hn truy cp n cc chng trnh da trn cc quyn truy cp ca ngi s dng u cui. Cc thnh phn c bn ca h thng ny bao gm qu trnh trn tn hiu, m ha cc kha in t m set-top box yu cu v h thng qun l thu bao. Bo mt IPTV khng ch x l vi cc quyn truy cp ca tng thu bao m cn phi bo v cc ni dung c lu tr trong mng v ti thit b ca khch hng. V cc ni dung ny thng lu c nh v di dng video s cht lng cao nn ri ro tng, chng l mc tiu hng n ca cc hacker. Chi ph cho vic bo mt tnh trn thu bao l mt yu t quan trng m cc nh cung cp dch v cn phi tnh n, do vy m hnh bo mt l yu t quan trng gim chi ph u t. u im ca cc th thng minh o, da trn phn mm l c th gim ti thiu chi ph khai thc v ti u bo mt bng cch cp nht chng trnh bo mt t mng, thay cho vic phi nh k thay i th thng minh da trn phn cng trong cc set-top box. Cc nh khai thc vin thng khi xy dng mng video IP da trn cc cng ngh bo mt hin c v tn dng u th ca cc cng ngh mi trong qun l bn quyn s (DRM) khi cc sn phm ny pht trin vi hng cc gii php tp trung vo phn mm. DRM cung cp mt h tng bo mt bo v tnh c nhn ca ni dung video IP, khng k ni dung ny l trong lung truyn ti hay ang c lu tr. DRM cng cung cp bo mt cho cc giao dch ca thu bao trong thanh ton v tnh cc. Cc gii php DRM s cn phi tch hp vi nhiu phn t trong mng IPTV, bao gm nn middleware, cc my ch VoD, cc set-top box cc thit b t nhiu nh cung cp khc. DRM tng cng cc quy nh s dng v do bo v ni dung khi vic s dng tri php khi n c truyn ti trn mng. Cc nguyn tc nh vy c th bao gm ngy qu hn xem, s ln c xem hay s ln copy. Mt s chc nng chnh ca h thng DMR bao gm: Cc k thut mt m ha s dng cho cc thnh phn xc thc v bo v chng li cc tn cng trn mng. Qu trnh xc thc ca cc thnh phn da trn DRM t c bng cch s dng ch k in t v m cp php.

Bn quyn s, c s dng biu th cc quyn ca ngi s dng, thng c gi trong phn cng ngn nga vic sao chp v chia s bt hp php. Lu tr bo mt gim st thng tin trng thi cp php, nh s cc ln phn ni dung s dng. Lu tr bo mt cho php s ln s dng hay khong thi gian s dng.

8. Cc giao thc mngNghin cu v IPTV s khng y nu thiu cc giao thc c s dng trong cc h thng ny. Cc giao thc ny gm cc giao thc truyn dn IP nh UDP v RTP v cc giao thc bo hiu nh RTSP v IGMP. Trong cc mng tin tin, cn quan tm ti nhiu loi giao thc khc nh MPLS, SIP v PIM..Tuy nhin, trong phn ny, chng ta s cp n cc giao thc chnh nh UDP, RTP, RTSP v IGMP thng gp trong qu trnh truyn ti ni dung IPTV. a) User Datagram Protocol (UDP) UDP c quy nh trong IETF RFC 768 v l mt trong cc giao thc chnh ca b cc giao thc IP. Thut ng datagram hay packet c s dng m t on d liu IP. Mi gi IP cha mt tp hp cc trng theo th t xc nh nh my thu bit cch gii m lung s liu. Nhiu loi giao thc c th c ng gi trong ti ca gi tin IP. Mt trong nhng u im chnh ca UDP l tnh n gin ca n, gim lng mo u so vi s liu trong ti cc mo u gi bao gm: a ch cng ngun 16 bit a ch cng ch 16 bit Trng di 16 bit Checksum 16 bit

Vi trng di 16 bit c th xc nh c gii hn 65.257 bit s liu m mt gi IP/UDP truyn ti. Hnh 2-7 minh ha qu trnh to khung gi IP.

Hnh 2-7: Dng gi IP.Trn thc t, di mt gi IP c th mang 7 gi lung truyn ti MPEG-TS (di 188 byte). Tuy nhin, UDP khng c c ch pht li v iu khin lung nh TCP.

Hnh 2-8: Cc gi IP/UDP/RTP.

b) Real Time Protocol (RTP) RTP c quy nh trong IETF RFC 3550 v IETF RFC 3551 v nh r dng gi truyn ti s liu audio v video. RTP gm hai phn lin quan cht ch vi nhau: Real Time Protocol: cung cp nhn thi gian, nh s th t chui v cc c cu khc kim sot vn nh thi. Qua c cu ny, RTP to ra qu trnh truyn ti s liu thi gian thc t u cui-ti-u cui. S dng qu trnh nh s chui cho php pht hin cc gi tin b mt v sai th t. Real Time Control Protocol: c s dng thu thp s liu gim st t u cui-ti-u cui, thng tin v qu trnh truyn pht, QoS.

Hnh 2-9: Mo u RTP.Cho d RTP c thit k khng ph thuc vo cc giao thc mng pha di, UDP vn c s dng rng ri hn. Khi truyn ti lung video MPEG-2, nhn thi gian RTP c ly t trc tip t xung nhp c ly mu 27 MHz trong PCR (Program Clock Reference) c ti trong lung, nh m bo ng b nh thi hn na. Tuy nhin, iu cn ch l RTP khng quy nh bt k c ch no khi phc cc gi b mt, m ch c th pht hin cc gi b mt nh m t trn. c) Real Time Streaming Protocol (RTSP) RTSP c quy nh trong IETF RFC 2326, cho php ngi s dng iu khin t xa my ch a phng tin tng t nh cc lnh iu khin VCR (Video Cassette Recorder), chng hn play v pause. Hnh 2-10 minh ha giao thc RTSP

Hnh 2-10: Giao thc RTSP.Thng thng, cc bn tin RTSP c gi t cc client, ngai tr mt s trng hp c bit, cc my ch gi ti client. Trong cc h thng IPTV, RTSP c s dng trong cc ng dng VoD khch hng c th truy cp v iu khin ni dung c lu ti cc my ch VoD. V bn cht VoD l qu trnh thng tin mt-ti-mt c thit lp qua phng thc unicast.

d) Internet Group Management Protocol (IGMP) IGMP c quy nh trong phin bn mi nht l IETF RFC 3376. IP multicating c nh ngha l qu trnh truyn dn gi tin IP ti nhm my ch. Nhm my ch ny c xc nh bng mt a ch IP duy nht. Trong h thng IPTV, nhm my ch s l tp hp cc thu bao mun thu mt chng trnh ring no . Trn thc t, iu ny c ngha rng cc h thng truyn dn s dng IGMP khng gi tt c ni dung ti tt c cc ngi dng. S dng IGMP cho php iu khin ni dung no n nhng ngi s dng no v do kim sot c lng s liu truyn qua mng ti mt thi im bt k. IGMP l giao thc c s dng trong h thng IPTV chuyn knh. p ng vi cc lnh iu khin t xa, mt lot cc lnh IGMP c to ra ri nhm multicast hin ti v nhp vo mt dch v khc. Thi gian cn thit thc hin nhng lnh ny c nh hng trc tip ti thi gian chuyn knh. Cc nh cung cp middleware ang thc hin rt nhiu k thut khc nhau ci tin thi gian p ng chuyn knh.

3. IPTV v Internet TVi khi IPTV b hiu nhm l Internet TV. Mc d c hai loi hnh ng dng ny u da trn c s cng ngh c bn ging nhau, nhng cc gii php trong qu trnh truyn ti video da trn IP khc nhau nh sau: H tng mng khc nhau: ng nh tn gi, Internet TV da trn mng Internet truyn ti ni dung video ti i tng s dng. Ngc li, IPTV s dng cc mng ring c bo mt truyn ti ni dung video ti i tng s dng. Gii hn a l: i tng s dng Internet khng truy cp c cc mng do cc nh khai thc vin thng s hu v vn hnh v bn thn cc mng ny c gii hn trong vng a l xc nh. Ngc li, Internet khng b gii hn v mt a l, qua mng Internet, i tng s dng c th truy cp ti dch v Internet TV t bt c v tr no trn th gii. Quyn s hu ca h tng mng: khi ni dung video c truyn ti trn Inetrnet, cc gi giao thc IP mang ni dung video c truyn ti c th b mt hoc tr, khi truyn qua cc mng khc nhau. Kt qu l, nh cung cp dch v video trn internet khng th m bo mc hi lng ca khc hng khi xem TV qua internet so vi TV truyn thng, TV cp hay TV qua v tinh. Trn thc t, tn hiu video qua internet i khi b git trn mn hnh v phn gii hnh nh hon ton thp. Ni dung TV cung cp n i tng s dng theo kiu best effort. IPTV c truyn ti trn h tng mng m nh cung cp dch v s hu. Vic s hu h tng mng cho php cc nh khai thc vin thng thit lp h thng ca mnh h tr qu trnh truyn ti video cht lng cao t u cui-ti-u cui. C cu truy cp: thng thng set-top box c s dng truy cp v gii m ni dung video qua h thng IPTV trong khi , truy cp ti dch v internet TV hu ht u s dng my tnh c nhn. Loi phn mm s dng trn PC ph thuc vo ni dung internet TV. V d, on file ni dung video c ti v t internet TV c khi yu cu phi ci t chng trnh chy file dnh ring xem. H thng qun l bn quyn (DRM) cng yu cu h tr c cu truy nhp ny.

Gi thnh: mt phn ng k ni dung video c truyn ti trn mng internet l min ph cho mi ngi. Tuy nhin, iu ny s thay i khi s lng ngy cng tng cc cng ty truyn thng a phng tin bt u a vo cc dch v min ph da trn internet TV. Cu trc gi thnh p dng cho IPTV tng t nh m hnh thu bao hng thng c chp nhn bi cc nh cung cp dch v TV tr tin. Nhiu chuyn gia phn tch cho rng s hi t ca internet TV v IPTV s thnh dch v gii tr ch yu sau ny. Cc phng php to ni dung: cc nh cung cp internet TV to ra phn ni dung video c kch thc xc nh v truyn vo cc knh, trong khi , cc nh cung cp dch v IPTV truyn trn cc knh cc phim v cc chng trnh truyn hnh thng thng do cc hng phim v hng truyn hnh ln cung cp.

4.

Kt lun

Cng ngh truyn hnh s to ra nhng ci tin v c bn so vi cc dch v truyn hnh tng t. S xut hin ca truyn hnh s mang li nhng li ch r rt v cht lng hnh nh, m thanh v kh nng truy cp ti nhiu dch v gii tr mi. IPTV l phng php mi truyn ti ni dung truyn hnh s trn mng v c xem l mt phn ca dch v triple-play thng c cc nh khai thc Vin thng trn th gii cung cp. Thut ng IPTV m t h thng c th truyn ti cc chng trnh truyn hnh trc tip, phim v cc loi ni dung video tng tc khc trn mng da trn IP. Cc thnh phn cu to nn mng IPTV ny gm cc h thng nh nh cc qu x l video, bo mt mng truyn ti. Cu trc h tng mng IPTV t u cui-ti-u cui c th bao gm tt c hay mt s cc thnh phn sau: Trung tm s liu IPTV chu trch nhim x l v chun b ni dung truyn ti qua mng bng rng. Mng phn phi IPTV bao gm nhiu phn t v cng ngh truyn ti ni dung IPTV t trung tm s liu ti cc i tng s dng. Thit b set-top box c lp t ti nh cc thu bao cung cp kt ni gia TV v mng truy nhp da trn IP. Mng trong nh ca khch hng cho php phn phi s liu, thoi v video gia cc thit b khc nhau.

Vi dung lng bng thng ngy cng cao v cc k thut nn tin tin cng vi nhu cu ca cc nh khai thc vin thng mun cung cp cc dch v video ti khch hng ca mnh l nhng yu t thc y th trng IPTV ton cu ngy cng pht trin. Vit Nam cng l mt trong nhng th trng IPTV y tim nng v ha hn mang li nhiu li nhun trong nhng nm sp ti. Tuy nhin, l mt cng ngh mi v ang dn hon thin nn hin nay trn th gii c nhiu t chc tiu chun ha tham gia vo qu trnh tiu chun ha ny nhm a ra c b tiu chun thng nht cho dch v IPTV