Kỹ thuật streaming trong mobile TV

PHAT THANH TRUYEN HINH<br /> <br /> <br /> <br /> <br /> 1<br /> <br /> <br /> :c;CO KY THUAT<br /> i_i p i #<br /> STREAMING<br /> TRONG<br /> a<br /> MOBILE TV<br /> <br /> ThS. Pham Dinh Chung, ThS. Pham Anh Thu<br /> <br /> <br /> 1 . G i a i THIEU CHUNG dang streamtag, Qng dung stream servtag, van de<br /> Traydn hinh di dbng (MobUs TV) li ebng nghe quan ly bang thbng, vi chuong trirta xem vi server<br /> ma hoi vi traydn din cic chuong trlrta traydn htah streamtag.<br /> hoac video de eb the thu dugc tren eie thiet bi di<br /> dgng nhu dien taoai dl dgng, cic thidt bi hd ttg sd 2. STREAMING TRONG MOBILE TV<br /> cam tay (PDA), eie thidt bi da phuang tien vb tuydn,<br /> Streamtag ngi dung (Am tharta, video) da ttb<br /> eie miy dien thoai cb kha nang thu tta bleu trayen<br /> thirta cbng nghe phd bidn cQng vbi sir phat trien<br /> binh di dbng [1].<br /> cua tatemet vio rtaimg nam 1990. Mbt phuong<br /> Vbi Mobile TV ngubi xem cb thd tray nhip mgt phip trayen tai du Ueu video db li ngubi su dung<br /> dai rbng cie chuong trlrta traydn htah trong khi di se tai vd eic file am tharta vi video vi bat dau xem<br /> ehuyen. Cie chuong trlrta trayen htah cb the duge chuang trirta khi da tai xong, phuang phip niy eb<br /> traydn tal ludng (streamtag) tbi may di dbng de xem nhugc diem li do kich thube eua eac file cb the lbn<br /> b tdc do gidng nhu khi phit; hoac cb the xem cic (vi du 20 Mbytes) nen thbi gian chb de tii ve li rat<br /> chuang trinh vbi ttd thbi gian hoae eb the dugc ghi dii.<br /> lal toin bb gidng nhu bang cassette video hoac dia<br /> 6 ehd do stteamtag du UBU am thanh vi vidso<br /> DVD. Mobile TV khbng chi eho phbp tmyen din mbt<br /> dugc phan phit true tiep tbi ngubi su dung dl dbng<br /> chieu thbng thuang mi cbn eho phep traydn tta bleu<br /> hoae eie thidt bi khie de xem trong khi vin tiep tue<br /> traydn hirta tuong tic rtab su dung eie kenh phan<br /> tal ve. Vi du, vbi kdt ndi 128 kbps, dQ Ueu video a<br /> hdi cung cap bbi mang te bio.<br /> tdc do 64-100 kbps eb the dugc traydn tal ludng Uen<br /> Tao ludng (Stieamtag) li mbt van de quan trgng tuc, eho phbp ngubi su dung tray nhap true tidp tbi<br /> trong mobile TV, arta hubng true tiep ddn ehat nbi dung da phuong tien.<br /> lugng dieh vu. Bii bio gibi thieu tdng quan vd ky Stteamtag thue hien dugc nhb su dung eic bb ma<br /> thuit streamtag trong mobile TV bao gdm khii hoi cb tdc do nbn cao, cimg vbi cbng nghe traydn<br /> mem vd strsamtag trong mobile TV, qua trirta bit til ludng ngi dung bing each bien ddi khubn dang<br /> giu vi ma hba nbi dung, bidn ddi file thirta khubn<br /> <br /> <br /> 38 TAP CHI CNTT&TT KY 1 (5.2010)<br />  PHAT THANH TRUYEN H I N H<br /> <br /> <br /> file du Ueu lim giu thirta khubn dang gbi phQ hgp Ueu stteamtag ddi vbi cae Qng dung. Vi du QmckTlme<br /> vbi vbi traydn tai qua mang tatemet. su dung ttnh ning Htat Tracks de eung cap thbng tta<br /> Cb hai phuang phip stteamtag: Du Ueu am thanh, dieu khien rtaim xac duta thbng tta am tharta vi<br /> video, eac ttang Web eb thd duge eung cap bing video da duge stteamtag.<br /> cich su dung giao thQe HTTP. Phuang phip niy duge 2.3 S t r e a m s e r v i n g<br /> ggi li tao ludng tisn tidn (progressive stteaming), vi Stteam servtag li mbt Qng dung die biet duge<br /> tauc hisn duge khi kerta phan phat eb kha nang phan su dung b ehd do cUent server de phit ehudi Uen<br /> phat dQ Ueu HTTP b eie tdc do bit yeu eiu. Phuong tuc cic gbi qua mang IP ddn may cUent. Ung dung<br /> phip thuc te hon db li phuang phip tao ludng thbi stteamtag sii dung cac giao thQc ttao ddi file thbi<br /> gian thue (real-time stteaming), phuong phap niy gian thue da phuang tisn duge phit tridn bai IETF.<br /> yeu eau su dimg eic giao thQc die biet (giao thQe Cie giao thue niy bao gdm: Giao thQe thbi gian thue<br /> tabi gian thire RTP, cic giao thQc multieasttag...) RTP, giao thQc dieu khien thbi gian thue RTCP vi<br /> vi cic server die biet (Apple QmckTlme server, giao thue tao ludng thbi gian thue (RTSP).<br /> RealTime server, Wtadows Media server).<br /> Qui trtah stteaming bao gdm hai kenh rieng re<br /> Stteamtag bao gdm cae bube sau: duge thiet lip cho phien stteaming. Kenh du Ueu<br /> - Bat glQ vi ma boa nbi dung; cung cap viec trayen tii dQ Ueu im tharta vi video,<br /> - Bien ddi file thinh khubn dang stteaming; ttong khi db kenh dieu khien eung cap phan hdi tQ<br /> stteamtag cUsnt (vi du nhu media player) tbi server.<br /> - Stteam servtag;<br /> Du Ueu am thanh vi video ttong qui trirta stteamtag<br /> - Trayen tai ludng qua cae mang IP;<br /> duge didu khien boi giao thQc RTP, giao thQe niy su<br /> - Chay chuong trtah tren media player. dung giao thue UDP vi IP lim cie lbp ben dubi. Do<br /> 2 . 1 Qua t r i n h b a t giu' va m a hoa n o i d u n g db du UBU dugc phan phit thso chudi datagram mi<br /> Viec bit giQ nbi dung bao gdm vise ttdp nhan khbng can xac nhin. Didu nay tao thirta kenh du<br /> dbng am taarta vi vidso a khubn dang tuong thieh Ueu ttong qui trlnh streamtag.<br /> vbi card bit giu video cua may ttnh hoac ssrvsr. CUent eung cap thbng tta nhu sd lugng gbi thu<br /> Khubn dang eb the li AVI hoae eic Qng dung chuyen<br /> Sefvtr dMIt<br /> nghiep, dang SDI. Card bit giu gdm eie bb ma hoi<br /> phan cQng cb the tidp rtaan nbi dung o khubn dang<br /> YC, RGB... Sau khi bit giu, cae file dugc luu giu tten<br /> dia vi du a khubn dang .avi trabc khi nbn. Sau khi IntaiMlcn<br /> nbn eie file dugc luu giQ a khubn dang nen phQ hgp /MConM,<br /> VMeoand<br /> nhu .mpg, .mp4,... phu thube vio bb ma hoi dugc<br /> sudung.<br /> 2.2 Bien do'i file t h a n h Idiuon dang s t r e a m i n g<br /> <br /> De cie file dugc trayen tai dbng stteamtag theg<br /> thbi gian thue, cic fUe niy can cb thbng tta didu<br /> khien thbi gian dd ssrvsr quan ly tdc do phit. Do db<br /> cie flls dugc bien ddi thirta khubn dang stteamtag<br /> bing cich them vio thbng tta dieu khien thbi gian<br /> Hinh 1 . Ngan xep giao thuc streaming<br /> vi metadata giup eho viee phan phat cb thQ tu du<br /> <br /> <br /> TAP CHI CNTT&TT KY 1 ( 5 . 2 0 1 0 ) 39<br />  PHAT THANH TRUYEN H I N H<br /> <br /> <br /> khdi niy duge bidn ddi thinh eic gbi RTP. Mdi gbi<br /> RTP bao gdm phan tieu dd vi du Ueu. Tieu dd cb<br /> phan mb ta dbng trayen tai, dau thai gian, vi sd thQ<br /> tu eua gbi dQ Ueu. Thbng tta niy rat can thiet trong<br /> viec ghbp lai eie gbi theo thQ tu chirta xic o miy thu<br /> dau cudi. Giao thQe RTP duy tri tdc do phan phit du<br /> <br /> <br /> <br /> il<br /> • 1 8«iMlft Ueu da duge ed dirta vi dugc thoi thuan qua kdt ndi<br /> UDP/IP, trong khi db giao thue RTSP hd trg su tuong<br /> tic cUent vbi eic ehQc nang rtau xem vi dimg tam<br /> Snaing thbi. Khi mbt kdt ndi duge thiet lap, RTSP dugc su<br /> dung de tao kdt ndi o tdc do bit cao rtaat mi mang<br /> Plays coiMMds<br /> IP hd trg (eb the gdm eic dubng Uen kdt vb tuydn<br /> RTCP RTSPL hoac cie mang GSM/GPRS hoae 3G, CDMA). Cac gbi<br /> trayen tai (im tharta vi video) duge xu ly Uen tuc<br /> Hinh 2 . Stream serving<br /> khi ChQng tbi media player. CUent can thuc hien luu<br /> duge vi ehat lugng kenh qua kbita RTCP. Server dua dsm du Usu vl tdc do bit traydn din thay ddi. Ndu tdc<br /> tren thbng tta thu duge se bidt ttah trang Idi vi tie do du Ueu thap hoic ty le ldi eao do didu kien dubng<br /> nghen eua mang vi tdc do mi cUsnt thuc su thu Uen kdt thi cUent se gm tta bleu tbi server yeu cau<br /> duge eie gbi. Nhb db ssrver eb the thue hien phin thue hien chuyen mach sang trayen til ludng thbng<br /> phit gbi b tdc do chtah xic. Vi du, dua tren thbng minh hoae do tdc do khung hi rbt. Qui trinh niy tao<br /> tin phan hdi tu cUent, server eb the chgn mgt trong thinh ket ndi don hubng (Unicast). Tuy nhien dang<br /> eae tdc do bit trayen tai dbng kha dung (ching ban kdt ndi niy khbng ly rabng khi cb mbt sd lugng lbn<br /> 64, 128, 256 kbps) hoae chgn tdc do khung thap ngubi su dung mudn tray nhip eimg mbt nbi dung,<br /> ban de dam bao tdc do du Ueu trayen til khbng vl khi db sd ludng trayen tai vi du Ueu duge eung<br /> vugt qui kha ning eua kerta IP. Kenh didu khien cap ting len nhanh chbng.<br /> su dung giao thue RTSP, giao thQe niy boat dbng Chd do trayen din khie li che do multicast, trong<br /> tren ndn giao thue TCP vi IP. RTSP do db didu khien db nhieu ngubi su dung cung thu dugc nbi dung, khi<br /> viec phin phit nbi dung streamtag tbi cUent qua<br /> mang IP. RTSP hd trg eie chue ning dieu khien nhu<br /> xem lai (playback), xem (play), tua di (forward), tua<br /> lal (rsvsrss) vi dimg tam thbi (pause), kdt hgp vbi<br /> media player cua cUent SB cung cap eho ngubi su<br /> dung day du chQc ning dieu khien trong qui trlnh<br /> xem lai qua tmyen tii dbng streamtag.<br /> 2.4 Streaming serving va quan ly bang<br /> thong<br /> <br /> Streamtag ssrvsr vi msdia cUent (Thiet lap kdt ndi<br /> ddn server dd trayen tii ludng) boat dgng b ehe do<br /> bit tay nhu mb ta tten Hinh 2.<br /> BtMUytr<br /> (y(y-o~(y(h<br /> Hinh 3. Truyen tai dong va ma hoa video MPEG-4 dupc phan IPp<br /> Dbng media dugc gui theo eie khdi du Ueu, cic<br /> <br /> <br /> 40 TAP CHI CNTT&TT KY 1 ( 5 . 2 0 1 0 )<br />  PHAT THANH TRUYEN H I N H<br /> <br /> <br /> tic nghen rtaat. SureStteam su dung chuyen mach<br /> stream dbng de chuyen mach tbi tdc do bit thap hon<br /> hoae cao hon phu thube vio dieu kien traydn din vi<br /> phan hdi tQ cUent. Vi du, SureStteam cb the chuydn<br /> tQ ludng 64 kbps sang ludng 128 kbps hoac nguge<br /> lai.<br /> Khubn dang RealMedia su dung giao thuc RTP vi<br /> giao thQc ban quyen RDP (giao Uiuc gbi du Ueu thuc)<br /> de trayen tai du Ueu. Hg cac giao thue RealMedia<br /> Hinh 4. Chuyen mach dong stream xay ra acac khung I. trayen tai du Ueu b chd do unicast.<br /> db du Ueu duge phit multicast. Cic bb dirta tuyen<br /> ttong mang thu duge dbng multicast thire hien phit 3. KET LUAN<br /> lap du Ueu tbi cac dubng Uen kdt khie ttong mang. Mobile TV la cbng nghe vb tuydn dugc thidt kd<br /> Thay vl hing trim nghta phibn unicast, mdi dubng de cb the traydn tal duge tta hieu traydn htah trong<br /> Uen kdt traydn tal chi mbt dbng nbi dung multicast. mbi trabng vb taydn di dbng eb bang thbng ban chd<br /> Phuong phip niy eb nhieu uu diem, tuy nhien cac vi thubng xuyen chiu arta hubng cua fadtag, nhidu<br /> cUent khbng cb eo ehd dieu khien de ybu cau server vi tap am, ttong khi phai dip Qng duge khi nang<br /> thay ddi tdc do bit trayen din khi xiy ra ldi hoae tic hien thi tta hieu tdt tten miy dau cudi cam tay dl<br /> nghen mang... dbng cb kich thube man htah nhb, cbng suat pta<br /> Vbi MPEG-4 cb co ehd khic de eung cap tdc do bit tisu thu hi ban chd. Streamtag li ky thuat chu ydu<br /> cao ban tbi eic cUent khi mang eb bing thbng eao dugc su dung dd traydn tai Un bleu Mobile TV tren<br /> hon. Server traydn tii dbng MPEG-4 se phit dbng eo mang 3G.<br /> sb cb do phin dai thap vi mbt sd dbng phii. CUent<br /> thu dbng ca sb vi cie dbng phu niy khi bang thbng Tai lieu t h a m khao<br /> kha dung lim cho chat lugng hinh inh tdt hon. [1] AMITABH KUMAR, iVIobiie TV: DVB-H, Df^B, 3G Systems<br /> 2.5 ChUtfng trinh x e m va server streaming and Rich IVIedia Applications, Elservier Inc, 2007.<br /> <br /> Cb mbt sd loai bb ma hoi vi server stteamtag, [2] BORKO FURHT, SYED AHSON, Handbool< of IVIobiie<br /> <br /> trong db mbt sd cbng nghe yeu eiu ban quydn rieng. Broa±asting: DVB-H, DIVIB, ISDB-T AND iVIEDIAFLO, CRC Press,<br /> 2008.<br /> Vi du su thiet lap streamtag eua RealNetwork gdm<br /> [3] CLINT SMFTH, DANIEL COLLINS, 3G Wireless Networks,<br /> bb ma hoi/giii ma RealVideo vi server stteamtag<br /> McGraw-Hill, 2002.<br /> SureStream. RealVideo dua tren nguyen ly ma hoi<br /> [4] DANIEL MINOLI, IP Multicast with Applications to IPTV and<br /> MPEG-4, su dung tdc do khung khbng lay miu. Didu<br /> IVIobiie DVB-H, John Wiley & Sons, 2008.<br /> niy eho phbp cae tdc do khung yeu cau ddi vbi toe<br /> [5] KAMEL HADDAD, DVB-H in Denmark Technical andEconomic<br /> do phan phat duge lira chgn dugc tao ra bing cac<br /> Aspects, Master's Thesis, Technical University of Denmark,<br /> vector chuyen dbng vi ngi suy khung. Do db mgt<br /> 2007.<br /> file msdia don gian cb the dugc tao ra cb cae tdc db<br /> [6] FRANK HARTUNG, UWE HORN, JORG HUSCHKE, MARKUS<br /> mi hoi khie rtaau. Khi thuc hien trayen tai ludng,<br /> KAMPMANN, THORSTEN LOHMAR, and MAGNUS LUNDEVALL,<br /> RealNetwork SureStream se thidt lap kdt ndi sau "Delivery of Broadcast Servtes in 3G Networks ", IEEE Transactions<br /> kW thoa thuan vbi khich hing. Tdc do du Ueu thap on Broadcasting, Vol. 53, No. 1, March 2007.<br /> nhat se dugc trayen tai ludng ttong dieu kien mang<br /> <br /> <br /> TAP C H I CNTT&TT KY 1 ( 5 . 2 0 1 0 ) 41<br />