ee Pm X 1Lp 11KTTTKH

MUC LUC MUC LUC ........................................................................................................ 1 N MUC N.................................................................................. 2 N MUC N ........................................................................................ 2 I. EvalVid- C cu cho truyn video v nh gi cht lng ..................... 3 11 Gii thiu ---------------------------------------------------------------------------------- 3 1.2 C cu v thit k ------------------------------------------------------------------------ 4 1.3. Cc chc nng h tr--------------------------------------------------------------------- 6 1.3.1.Xc nh tn tht gi tin v tn tht khung .............................................. 6 1.3.2.nh gi cht lng video ....................................................................... 9 14 Cc cng c ----------------------------------------------------------------------------- 11 1.4.1. Cu trc d liu v files .......................................................................... 11 1.4.2. B gi video- VS ...................................................................................... 12 1.4.3. ET Evaluate Traces .............................................................................. 13 1.4.4. Fix Video- FV .......................................................................................... 16 1.4.5. PSNR- nh gi cht lng .................................................................... 18 1.4.6. Tnh ton MOS ........................................................................................ 19 1.4.7. Nhm cng c th 3 cn thit ................................................................. 20 15 Cc kt qu lm mu --------------------------------------------------------------- 21 16 Kt lun v cc ch cho vic nghin cu sau ny ------------------------------ 22 II. Assignment ................................................................................................ 23 21 M ha ----------------------------------------------------------------------------------- 23 22 Gii m ----------------------------------------------------------------------------------- 25 23 Thit lp mng v truyn file --------------------------------------------------------- 26 L M O ............................................................................ 27 ee Pm X 2Lp 11KTTTKH

N MUC N nh 1: S c cu nh gi cht lng Video ......................................... 4 Hnh 2: Video CBR MPEG-4 vi tc bit ch 200 kbps ......................... 7 Hnh 4: V d PSNR (video ging nhau c gi i nhng b tn tht t nhiu) .............................................................................................................. 19 Hnh 5: V d v video c phn loi theo MOS (truyn dn video ging nh trong hnh 4)........................................................................................... 20 Hnh 6: V d v nh gi cht lng video (mc MOS) vi EvalVid 21 Hnh 7: V d v vic nh gi cht lng video (s ca ngi s dng c tha mn) vi EvalVid ........................................................................ 22 N MUC N Bng 1: Cht lng ITU-R v mc suy yu .......................................... 10 Bng 2: Possible PSNR to MOS conversion ............................................... 11 Bng 3: D liu lin quan cha trong video trace file ............................... 12 Bng 4: D liu lin quan cha trong sender trace file gm c time stamp, packetv packet size. File ny c to ra ri rc bi v n c th thu c t cc cng c khc (v d TCP-dump, xem ti liu tham kho). .............................................................................................................. 12 Bng 5: Th t gii m v hin th khung MPEG ..................................... 17 ee Pm X 3Lp 11KTTTKH

I. EvalVid- C cu cho truyn video v nh gi cht lng Vi EvalVid, chng ta gii thiu mt c cu hon thin v mt cng c nh gi cht lng video c truyn trn mng truyn thng thc hoc m phng Ngoi vic o lng cc tham s cht lng dch v ca mng v d nh tc tn tht, tr, v bin tr (jitter), n cn a ra vic nh gi cht lng video mt cch ch quan cho video thu c da vo vic tnh ton PSNR tng khung mt Cng c c b ch to theo kiu modungip n c th trao ivi c mng v b m ha-gii m o co ny gii thiu ng dng ca n cho MPEG-4 EvalVid to mc ch cho cc nhnghin cu mun nh gi vic thit k mng ca h hoc nh gi s ci t xt v s cm nhn ca ngi s dng1.1. ii thiu Ngy nay c rt nhiu cc h thng vin thng cung cp vic truyn dn thi gian thc theo kiu khc nhau, truyn video c cho l mt trong nhng ng dng quan trng nht ca h thng vin thng S pht trin ngy cng tng ny lm cho chtlngvideochtrtrthnhmtvnangcquantmMcd nhiubibonghincuvcccchhtrchtlngdchvQoSchocc mng khc nhau th vn c rt t bi bo h tr vic nh gi c tnh thng nht v tnh so snh cht lng thc s thu c bng s cm nhn c nhn Trong thc t, nhiu nh nghin cu hn ch mnh chng minh rng c ch trong nghin cu c th gim c t l mt gi, tr gi hoc bin tr v h cho rng nhng php o ny l nh gi cht lng video thu c Tuy nhin, ngi ta bit c rng cc tham s c m t trn khng c chuyn i d dng v duy nht vo mt cht lng chovic truyn tiVideo Tc l vic chuyn inycth khc nhauphthucvophngthcmha,phngthcchegiutnthtvxl tr/bin tr Cccngcchungcsnchovicnhgichtlngvideothnggi thuytrngcckhungcngbtiphaphtvphathu,cnghalchng khngthtnhtonchtlngvideotrongtrnghpkhungbmthocccli giimkhungChnghnnhphnmmJNDmetrix-IQ,vdnAQUAVIT. Nhng cng c ny khng ph hp nh gi cho khung video nhn c khng hon thin Chng ch c th p dng cho cc khung video ti ni m mi khung c thcgiimtiphathuNhngnhnghincukhcnhgichtlng videokhidngkhungvideobbindngtronglctruyn,khngchophpphn ee Pm X 4Lp 11KTTTKH

mm ca h c th dng cmt cch cngkhai Theo s hiu bit ttnht ca cc tc gi th cha c cng c min ph tha mn cc yu cu c m t trn Bo co ny gii thiu v EvalVid N l mt c cu v mt cng c nh gi thng nht v cht lng truyn ti video EvalVid c cu trc khi, lm cho n cthtraoitheomuncangisdngchochthngtruyntilncc codecs V vy n c p dng cho bt k phng thc m ha no v c th c dngctrongcccitthcnghimthtvthnghimmphngCcdngc cthchinISO-CtinhkhitchotnhkhchuyntiaTtccctngtc vi mng c thc hin thng qua hai trace files Do n d dng c tch hp EvalVid trong bt k mi trng no Cu trc ca bi bo ny nh sau: Phn 2 gii thiu tng quan v ton b c cu Phn 3 gii thch phm vi ca cc phn t chc nng h tr Sau cc cng c c nhn c m t chi tit hn trong phn 41.2. C cu v thit k Hnh 1 cho thy cu trc ca c cu EvalVid S tng tc gia cng c thc hinvlungdliuckhiuhaCigctnhtonscgiithch trong phn 3 v phn 4 cho thy n thc hin bng cch no v t thu c cc kt qu Hnh 1: S c cu |nh gi| cht lng Video Cngthnh1,qutrnhtruynvideosycbtutvicm ha thng tin t ngun, ng gi, truyn qua mng, gim jitter bng b m ti to, ee Pm X 5Lp 11KTTTKH

gii m v hin th cho ngi s dng Hn na cc im ti d liu c rt ra t lung truyn dn c nh du Thng tin ny c lu tr trong cc file khc nhau Cc file ny c dng thu thp kt qu mong mun v d nh, t l mt gi tin, jitter v cht lng videoRt nhiu thng tin l cn thit tnh ton cc gi tr nyD liu cn thit l (t bn gi): -vde c b c -video c m ha -nhn thi gian v loi gi tin c gi V t bn nhn -nhn thi gian v loi gi nhn c -tp hp li video c m ha-video gii nn gc c hin th Vic nh gi cc d liu ny c thc hin ti bn gi v vy cc thng tin tbnnhncnphigilichobngiTrnthctthvideogcchannc dung lng rt ln v d 680 M i vi cho 3 pht video trn mn hnh PDA Mt khc, c th ti to video c hin th t cc thng tin sn c bn gi Thng tin duy nht cn thit t bn nhn lmt file cha cc nhn thi gian cami gi tinthuciunythuntinhnnhiusovivictruynccfilevideo hon thin (sai s v m ha) t bn nhnX l cc d liu thc hin trong ba giai on Giai on u tin i hi cc nhnthigiantchaibnvccloigitinCcktqucabcnylbit c loi khung da vo t l mt gi v tr gia cc gi Hn na, sai s file video tbnnhnctitobngcchdngfilevideogccmhavthngtin tn tht gi Video y c th c giim thnh cc khung video gc c hinthchongisdngTiimny,vnchungcavicnhgicht lng video c thc hin Cc chun o cht lng video lun lun i hi vic sosnhkhungchinth(cthbbini)vicckhunggctngng Trng hp cc khung hon ton b mt th vic ng b khng th c duy tr. Giai on th hai ca qu trnh ny a ra mtbin php gii vn ny Davothngtintntht,ngbkhungchiphcbngcchxenkhung c hin th sau cng cho mi khung b mt iu ny lm cho vic nh gi cht ee Pm X 6Lp 11KTTTKH

lngtthnDo,filevideogccnhvfilevideogccdngtigiai on cui thu c cht lng videoCchptronghnh1ctnlVS,ET,FV,PSNRvMOSlccchng trnh m c cu vic nh gi cht lng c Tng tc gia cc cng c v mng (c xem nh l hp en) da vo cc trace files Cc files ny cha tt c cc d liu cn thit Ch c mt file cn phi c cung cp t ngi s dng EvalVid l receiver trace file Nu mng l mt ng lin kt thc t th file ny c to ra tTCP-dumpNumngcmphngthfilenytorabithnhphnbn nhn ca s m phngi vi cc cng c nm trong EvalVid ngi ta ch cn cc trace file ny, file video gc v b gi m thui Do , trong trng hp EvalVid th mng ch l mt hpenmtoratr,tnthtgivvicspxpligitinNcthlmt ng lin kt thc, chng hn nh mng Ethernet hoc l WLAN, hoc m phng ca mng Do tng tc ca EvalVid vi mng ch c biu din bi hai trace file (bn gi v bn nhn), c th d dng thay hp mng lm cho EvalVid cng tn cy hn Tng t, b codec video cng c th c thay mt cch d dng 1.3. Cc chc nng h tr Phn nym t v cc tham s c tnh ton bicng c ca EvalVid, cc khi nim hnh thc v cc ti liu tham kho cho vic nghin cu su hn i vi vn ny c bit l vic nh gi cht lng video uc cho bit 1.3.1.Xc nh tn tht gi tin v tn tht khung a.n tht gi Vic mt gi tin thng c xc nh da trn c s k hiu nhn dng gi Do , hp en mng phi cung cp ID gi duy nht iu ny khng phi l vn i vi vic m phng bi v cc ID duy nht c th ddng c pht Trong cc php o, cc ID gi tin thng c ly t IP (cung cp mt ID duy nht) ID gi duynhtcngcsdngdhybvicspxpligiTrongtrnghp truyn dn video, n khng ch cp n vic l bao nhiu gi b mt m cn cho bit v loi d liu nm nm trong cc giV d, b codec MPEG-4 nh ngha 4 loikhcnhaucakhung(I,P,,S)vcngnhdngmtsphnmou chung Do n rt cn thit cho truyn dn video v rng loi d liu no b mt th n cng cn thit phn bit cc loi gi tin Vic nh gi tn tht gi tin c tnhphthucvoloigiTnthtgicnhnghatrongphngtrnh(1) tnh theo . ee Pm X 7Lp 11KTTTKH

Tn tht gi100nTrecvPLTnTsent= (1) Trong T:loi ca d liu trong gi (mt trong tt c, mo u, I, P, , S) nTrecv: Tng s gi tin loi T c gi nTsent: Tng s gi tin loi T nhn c b.n tht khung Mt khung video (thc ra l mt nh tnh n c m ha) c th tng i ln, khng ch trong trng hp tc bit video bin i m cn trong tc bit c nhladothutngkhngicpdngchostrungbnhchokhongthi gianngnCckhungIthnglnngksovitcbtchkhngi(s trung bnh thi gian ngn) thm ch trong CR videos (hnh 2). Rt c th v c kh nng rng mt s hoc c th l tt c cc khung ln hn nvtruyntia(MTU)camngMTUlkchthcgitiachtr bimng(vdEthernet=1500bytesv80211bWLAN=2312bytes)Cc khungnycnphicphnonthnhccginhhnphhpchoMTU camngViccthphnoncckhungnyaramtvnchovictnh ton v tn tht gi Hnh 2: Video CBR MPEG-4 vi tc bit ch 200 kbps V nguyn tc th tn tht gi c th thu c t tc tn tht gi ( y, gi lun mang ngha l gi IP) Nhng qu trnh ny ph thuc t vo kh nng s dng b gii m video thc bi v mt s b gii m c th x l mt khung tuy mt s thnhphncakhungbmtvmtsbgiimthkhngthHnna,mt ee Pm X 8Lp 11KTTTKH

khung c th c gii m da vo gi no ca n b mt Nu gi th nht b mt thkhunggnnhkhngbaogicgiimDo,cctnhnngcaccb gii m no cn phi quan tm n tnh ton tc tn tht khung N c tnh ring cho tng loi khung Tn tht khung 100nTrecvFLTnTsent= (2) Trong T: kiu ca khung (mt trong tt c mo u, I, P,, S) nTrecv: Tng s gi loi T c gi nTsent: Tng s gi loi T nhn c c.Xc nh tr v bin tr- Jitter Trongcchthngtruynvideokhngchstnthtlquantrngchocm nhn cht lng video m phi quan tm n mt s tham s khc nh tr cc khung v bin tr-Jitter Video s lun cha cc khung c hin th vi tc khng i Vichin thmt khung trchoc sau khithi giannht nh dn n git hnh. Vn ny c gii quyt bng b m ti to Cc b m ny nhm mc ch hp th jitter c to ra bi cc tr mng R rng mt b m ti to ln c th b li bt k s lng jitter Trong trng hp c bit b m ln n mc cha ton b video v vic hin th bt u m khng cn ch n khi nhn ckhung cui cng iu ny s loi b bt k jitter c th c nhng phi c thmtrchotonbthigiantruynMttrnghpcbitkhcslmtb m c th cha ngmt khung Trong trng hp ny khng th loi b bt k jitter no nhng li khng c tr thm no c to ra c cc k thut tinh vi c pht trin cho cc b m ti to ti u gii quyt s cn bng c bit ny. Cc k thut ny khng nm trong phm vi c cu cmtDunglngbmtitolthamschoqutrnhnhgicht lng. iu ny ang hn ch c cu ny v cc b m ti to tnh Tuy nhin, do vic tch hp b m ti to lin quan n qu trnh nh gi, th s xy ra tn tht mi do trn b m ti to hoc thiu b m nhnghahnhthccaJittercsdngtrongbibonyccho trong phng trnh 3, 4, v 5 l s thay i v tr gia cc khung lin tip hoc ee Pm X 9Lp 11KTTTKH

trgiaccgilintipFrametimectnhbngthigiantiongi cui cng ca khung phn on c nhn Tr gia cc gi lin tip 00itP =(3) 1it t tpP Pnnn= Trong tPn nhn thi gian ca s gi n Tr gia cc khung lin tip 00itF = 1it t tF F Fm mm= Trong tFml nhn thi gian ca on gi cui cng ca s khung m Packet jitter 12( )1Nj it iti P NNi= = (4) Trong N:tng s gi itN: l tr trung bnh gia cc gi lin tip Frame jitter 12( )1Mj it iti F MMi= =(5) Trong M: tng s khung itM: tr trung bnh gia cc khung lin tip Ccbiuthngkchotrgiaccgilintipvkhunglintipcng c tnh ton bng cc cng c ca c cu ny (xem phn 43) 1.3.2.nh gi cht lng video Vic nh gi cht lng video scn phi da vo cht lng cm nhn ca ngi dng bi cm gic ca ngi dng l ci cui cng C hai phng php cbnnhgichtlngvideolnhgichtlngchquanvphp nh gi khch quan Cc chun o cht lng ch quan lun nm c yu t quan trng,cmgiccangidngxemvideokhichngcckttin:rttnthi gian, yu cu nhn lc cao v cng c c bit Cc php nh gi khch quan c mtchititbiITU,ANSIvMPEG.cmnhnchtlngcaconngi ee Pm X 10Lp 11KTTTKH

thng c cho theo mc t 5(tt nht) v 1 (xu nht) nh trong bng 1 Mc ny c gi l im tri nghim trung bnh (Mean Opinion ScoreMOS). Bng 1: Cht lng ITU-R v mc suy yu Nhiu cng trnh trong cng nghip v nghin cuyu cu phng php t nghanhgichtlngvideoCcthnghimphctpvttinca phngphpchquanthngkhngcpdngDo,phngphpkhch quan c pht trin cnh tranh vi cm gic cht lng ca h thng th gic ca con ngi (HVS) Tuy nhin, phng php ph bin nht l vic tnh t s tn hiu nh trn tp m (PSNR) cho mi nh tnh T s ny l mt trng hp c bit ca t s trn tnhiutrntpm(SNR)SNRsosnhnnglngtnhiuvinnglngtp m T s PSNR so snh nng lng tn hiu ti a vi nng lng nhiu N c kt qutngquanvicmnhnchtlngchquancaohnsovitsSNR. Phng trnh (6) l nh ngha ca PSNR gia thnh phn sng Y ca nh tnh ngun S v nh tnh ch D ( ) 20log1021( , , ) ( , , )0 0VpeakPNSR ndBNNcol rowY n i i Y n i jD SN Ni j rowcol| | | | | | | (| |\ .= = = (6) 2 1kVpeak = k :tng s bit trn mt pixel (thnh phn sng) T s c c th gi l sai s trung bnh bnh phng (MSE) Do , biu thc PSNR c th vit tt thnh: ee Pm X 11Lp 11KTTTKH

20logVleakPSNRMSE= , Do PSNR c tnh cho tng khung th n bt tin khi p dng cho video gm hng trm hoc hng nghn khung Hn na, ngi ta thng quan tm n s mo dng c to ra bi mng V vy h mun so snh video thu c (c th b mo) vi video khng b mo gi i iu ny thc hin bng cch so snh PSNR ca video c m ha vi video thu c cho tng khung hoc so snh cc trung bnh ca n vi lch chun MtphngphpnalutinphitnhMOS(bng2)vtnhstl khung vi MOS xu hn t s khung ca video c gi (khng b mo dng) Phng php ny c u im l thy r s bin dng gy ra bi mng Trong phn 4, ta c th thy v d c cho bi cng c MOS ca EvalVid Cc kt qu r hn c cho bi EvalVid c tm tt trong phn 5 Bng 2: Possible PSNR to MOS conversion 1.4. Cc cng c PhnnygiithiucccngccaccuEvalVid,mtvmcchv cch s dng ca n v cho thy cc v d v kt qu thu c Ngoi ra, phn ny cn cho bit v cc ngun ca file video mu v cc b codecs1.4.1. Cu trc d liu v files u tin, cn mt ngun video Raw (cha m ha) video files thng lu tr di dng YUV, bi v dng ny l dng u vo c u tin hn i vi cc b gii m c sn Files kiu ny c th thu c t nhiu ngun khc nhau, chng hn nh cc b codec min ph MPEG-4. Cc khung video mu cng c th thu c t tc gi ee Pm X 12Lp 11KTTTKH

Khi c c file video c m ha (cc lung bit), trace files c to ra t n Cc trace files ny cha tt c cc thng tin lin quan cho cc khi cng c ca EvalVid thu c cc kt qu nh trnh by trong phn 3 Cc cng c nh gi cht lng video to ra cc on chng trnh c v vit cc trace files ny v s dng cu trc d liu trung tm cha tt c cc thng tin cn thit a ra cc kt qu mong mun Dng thc ca trace files, cch s dng cc on chng trnh vnhnghacutrcdliutrungtmcmtngngntrongphnsauv c m t chi tit trong ti liu tham kho 1.4.2. B gi video- VS iviccfilevideoMPEG-4,bphntchcphttrindavo chunvideoMPEG-4;simpleprofilevadvancedsimpleprofilecthchin iu ny lm cho n c th c c bt k file video MPEG-4 c to ra bi b gii m thch hp Mc ch ca b VS l phi to ra mt trace file t file video c m ha Mt cch ty , file video c th c gi i qua UDP (nu h thng quan st l mt thit lp mng) Cc kt qu t VS l hai trace files cha cc thng tin v mi khung trong file video v mi gi c to ra truyn dn (bng 3 v bng 4) Dng ca video trace file: Th t khungLoi khungChiu di khungS gi UDPThi gi 0H241 segm40 ms 1I937910 segm80 ms 2P25493 segm120 ms 3B5501 segm160ms Bng 3: D liu lin quan cha trong video trace fileTime stamp [s]Packet IDPayload size 102910404.014760Id 48946Udp 24 102910404.048304Id 48947Udp 1024 102910404.048376Id 48948Udp 1024 Bng 4: D liu lin quan cha trong sender trace file gm c time stamp, packet ID v{ packet size. File n{y c to ra ri rc bi v n c th thu c t cc cng c khc (v d TCP-dump, xem ti liu tham kho). Chaitracefilesnybiudinvictruyntivideohonthin(tibngi) v cha tt c cc thng tin cn thit cho vic nh gi su hn bng EvalVid i vibVS,chngtacthtoramtcptracefilesnychoccfilesvideokhc ee Pm X 13Lp 11KTTTKH

nhauvvichiudigitinkhcnhauSauccfilenycthcavo hp en mng (chng hn nh s m phng) iu ny c thc hin vi s h tr t cc on chng trnh u vo v cc cu trc d liu cung cp bi EvalVid Sau mng s to ra tr v tn tht v s sp xp li cc gi tin Mt trace file khc ti bn nhn c to ra hoc vi s h tr ca on chng trnh u ra ca EvalVid hoctrongtrnghptruyndnthcchbiTCP-dump(ntoratracefiles tng thch vi EvalVid) CnlurngmcdlpIPsphnonccgiUDPtrnMTUcalp pha di v lp IP s c gng tp hp li cc on gi ti bn nhn th tt hn hy cho n t phn on Nu mt on gi (IP fragment) b mt th ton b gi (UDP) c coi l b mt Do n thch hp hn c c phn cn li ca cc on gi tin th bo co ny mun khuynnghchng ta nn s dng chc nng phn on gi MTU ca VS nu c th1.4.3. ET Evaluate Traces im trung tm ca c cu nh gi cht lng l mt chng trnh c gi l ET (Evaluate Traces) y thc hin php tnh ton thc s cho tn tht gi tin v tn tht khung v cng nh tr v bin tr (jitter) i vi victnh ton cc d liu ny ch yu cu ba trace files bi v n y c y tt c cc thng tin cn thit tnh ton tn tht v jitter, thm ch k c loi khung, loi gi cng bit Vic tnh ton tn tht rt d dng ch nh vo tnh c sn ca ID gi duy nht Nh vo video trace file, mi gi c phn loi Mi gi ca loi ny khng cha trong trace file bn nhn th c xem nh l b mt T l tn tht da trn loi gi c tnh ton nh phng trnh (1) Tn tht khung c tnh ton bng cch tm bt k khung no, nu mt trong nhng on khung (cc gi) b mt Nu on u tin ca mt khung nm trong cc on b mt th khung c xem l b mt iu ny l do b gii m video khng th gii m mt khung m thnh phn u tin b mt Tn tht khung da trn loi c tnh ton theo phng trnh (2)Di y l mt v d cho u ra ca ET i vi cc tn tht (mt truyn dn video ca 4498 khung trong 8301 gi) ee Pm X 14Lp 11KTTTKH

Trgiakhunglintipctnhtheophngtrnh(3)v(4)Tuynhin, trong trng hp tn tht gi, cc biu thc ny khng th p dng d dng c iu ny do trong trng hp ny khng c time-stamp c sn trong trace file bn nhn cho cc gi tin b mt Do c mt cu hi t ra rng tr gia cc gi lin tip c tnh bng cch no, nu t nht mt trong hai gi lin tip b mt? Mt kh nng l phi t tr gia gi lin tip trong trng hp gi b mt vi gi tr error v d gi tr 0 Sau nu mt gi thc s nhn c, th c th tm kim phn hi chonkhitmthymtgitrngTrongtrnghpnytrgiaccgilin tipsl _ _nlast received packett t iunycnhcimlkhngnhnc mt gi tr cho mi gi v tr gia gi lin tip c th tng qu ln l l do ti sao phng php c s dng bi ET l hi khc nhau Nu t nht mt (trong hai gi thc s c dng trong vic tnh ton) gi b mt th s khng c gi vi gi tr ng nhng gi vi gi tr d on iu ny c thc hin bng cch tnh thi gian nc th gi nh c chomt gi bmt Di ys cho thy cch ny thc hin nh th no v phng trnh (7) iu ny thc t c ngha l i vi cc gi tin b mt th gi tr ca tr gia cc khung lin tip ti bn gi c dng Nu gi tin tng i t b mt th phng php ny khng tc ng ng k cho thng k Jitter Mt khc, nu c t l tn tht rt cao th mt phng php khc c gii thiu: tnh ton cc gi tng i nhn c v tnh cc gi b mt mt cch ring bit Thi gian n (gi b mt)( )1 1t t t tR R S Sn nn n= + (7) Trong tSn: time-stamp ca s gi n c gi tRn: time-stamp ca (khng) s gi n c nhn n y, do mi gi tin c time-stamp ng th ngi ta c th tnh tr gia cc gi lin tip theo phng trnh (3) Hnh 3 cho mt v d v cc tr gia cc gi lin tip c tnh bi ET ee Pm X 15Lp 11KTTTKH

Hnh 3: Mt v d v tr gia gi lin tip ET cng c th tnh n c khi tn ti cc gii hn thi gian nht nh Nu c mt b m ti to c thc hin ti bn nhn ca mng (b m ny s rng khikhngckhungnoinvithigiannhtnh)thbmtitoc chiu di ti a Php nh gi cht lng khch quan chng hn nh vic xc nh PSNR khng th tnh n tr hoc jitter c Tuy nhin, mt b m ti to rng (hoc y) lm cho mt gi tin (khng c khung no c hin th) Chiu di ti a b m ti to c th c dng bin i tr thnh tn tht gi Vi ET, ta c th thc hin iu ny bng cch cung cp chiu di ti a b m nh l mt tham s Sau s ghp hp ca tr vi tn tht c thc hin nh sau: MtnhimvkhcmETthchinltoramtvideofilebli(dotn tht)Fileblinylcnthitthchinvicnhgichtlngvideocho cui - n cui Do mt file khc l cn thit lm u vo cho ET N c tn lfilevideocmhangunTheonguyntcvicphtravideoblic thc hin bng cch sao chp video gc cho tng gi ti ch m cc gi b mt c ee Pm X 16Lp 11KTTTKH

biNgitaphichnsaischatrongtnhnngcabgiimc dng C thnirngb giimmongmun nh duc bit trong trng hp cc d liu b mt v d cc t m c bit hoc n gin l mt b m rng (hoc chaccbt0)thayvmtgibmtTacnphitmhiutrongtiliumlin quan n b codec video m ta c mun s dng 1.4.4. Fix Video- FV nh gi cht lng video s c thc hin cho tng khung C ngha l ta cn thc s nhiu khung ti bn nhn nh ci ti bn gi Do c mt cu hi t ra rng cc khung b mt s c tnh nh th no nu b gii m khng to ra c cckhungrngchocckhungbmtCngcFVchcdngnubcodec c s dng khng th cung cp cc khung b mt Cc khung c x l nh th no bi FV c m t sau ny trong phn ny Cn mt s gii thch v cc dng video. Raw video formats: Video s l dy cc nh tnh Khng quan tm n vic dy ny c m ha nhthno,nuchbngcchlidngdthakhnggian(chnghnnh Motion-JPEGThtranlmtdycaccnhtnhJPEGcmha)hoc cng bng cch li dng d tha thi gian (nh MPEG hoc H263) th cui cng mibcodecvideostoramtdyccnhtnhth(pixelbypixel)sau chinthThngthngccnhtnhthnychlmtmnghaichiuca pixels Mi pixel c cho biba gi tr mu (mu , xanh l cyv mu xanh) Tuy nhin, trong vic m ha video, cc pixels khng c xc nh biba gi tr mu nynhng n c xc nh bi s kt hpca 1 gi tr sng v2 gi tr cathnhphnmuChaiphpxcnhucthcbinichonhau (phng trnh 8) do n tng ng nhau Ngi ta cho rngmt ca con ngi rt nhycm vi thnhphn sng hnvithnhphnmucamtbcnhlldotisaotrongvicmha videothnhphnsngctnhtonchomipixelcnhaithnhphnmu thng c tnh trung bnh trn4 pixels Ci ny chia i s lng d liu c giiivimipixelsoviphngphpRGCnhiuphngphpthuc kiu ny c gi l m ha YUV, chi tit trong ti liu tham kho.Y = 0.299R + 0.587G + 0.114B(8) U = 0.565(B Y) V = 0.713(R - Y) ee Pm X 17Lp 11KTTTKH

R = Y + 1.403V G = Y 0.344V 0.714V B = Y + 1.770U Qu trnh gii m ca a s b gii m c kt qu l cc files video th trong dng YUV gii m MPEG-4 m t ny s dng vit di dng YUV files vi 4:2:0h t gii m v hin th Chun MPEG v c bn nh ngha 3 loi khung c tn l khung I, khung P, khungCc khung I cha mt nh tnh hon thin (c gii m c lp, ch d thakhnggianclidng)CckhungIlcckhungcmhaniCc khung P l cc khung d on (n cha thnh phn c m ha ni cng nh cc vectorchuynngctnhtonphthucvocckhung(IhocP)trc) Vic m ha khung loi P cn c d tha khng gian v thi gian Cc khung ny chcgiimhontonnukhungIhockhungPtrccthtnhc Cckhungcmharingphthucvocckhunglintipvtrc(I hoc P) Cc khungch li dng d tha thi gian Khung loi ny hon ton c th c giim nukhung trc v khung lin tip I hoc P c th tm c lldotisaoMPEGspxplicckhungtrckhigiivvybtk khung no nhn c c th c gii m ngay lp tc, xem bng 5 Th t hin thLoi khung Th t gii m 1 2 3 4 5 6 I B B P B B 2 3 1 5 6 4 Bng 5: Th t gii m v hin th khung MPEG Do vn v vic sp xp li ny, mt khung c m ha khng tng ng vi khung (YUV) c giimvi s th t nh nhau FV gii quyt vn ny bngcchghpphhpcckhung(YUV)vicckhungcmhadavo bng 5 C th c nhiu cch thc m ha hn l ci c cho thy trong bng ny (vd,cchthcmkhngccckhungloi,vichmtkhungnmgia hoc nhiu hn hai khunggia hai khung I (hoc P) nhng v nguyn tc v vic sp xp th t l lun lun ging nhau ee Pm X 18Lp 11KTTTKH

Handling of missing frames Mt vn khc c gii quyt bi FV l s ghp khng ph hp c th c gia tng s khung c m ha vi tng s khung gc xy ra bi s mt gi S ghpkhngphhpslmchovicnhgichtlngvideokhngthchin c Mt b gii m t t c th gii m mi khung mc d nhn c tng phn Mt s b gii m t chi gii m cho tng phn ca cc khung hoc ch gii m cc khung loi , ni m mt trong nhng khung b mt c suy ra it c vic x l cc khung b mt hoc cc khung b li nh vo vic s dng b gii m th FV c th c a vo khc phc cc nhc im ca b gii m Vic x l lun bao gm vic xen cc khung b mt C hai cch cho vic x l ny Th nht l phi xenmt khung rng chomikhung (cha cm ha) Khung rng l mtkhungkhngchamtthngtinnoKhungrngslmchoccbgiim nohinthmtbcnhen(hoctrng)Phngphpnykhngphail phng php thng minh do s chnh lch thp gia cc khung lin tip V vy FV s dng phng php th hai (l php xen mt khung c m ha cui cng thay v mt khung rng trong trng hp mt khung ca b gii m Vic x l ny c u im hn khi ghp ph hp cho tnh trng ca mt video player tht 1.4.5. PSNR- nh gi cht lng PSNRlcschophpochtlngtrongccutrnnhgicht lng video thu c Vic xem xt s chun b cc thnh phn s b ca c cu th victnhtonPSNRlmtqutrnhngincmtbiphngtrnh(6). Tuy nhin, cn phi lu rng ngi ta khng tnh c PSNR nu hai nh tnh l tng ng nh phn iu ny l do trong lc ny sai s trung bnhbnh phng bngkhngvdoPSNRkhngthtnhtheophngtrnhs(6)cDo ngi thng tnh PSNR gia file video th bn gc trc qu trnh m ha vi ci file video nhn c iu ny m bo rng s lun lun c sai khc gia cc nh tnh th bi v tt c cc b codecs video hin i u b tn tht ee Pm X 19Lp 11KTTTKH

Hnh 4: V d PSNR (video ging nhau c gi i nhng b tn tht t nhiu) Hu ht cckt qu dng PSNR ch s dng thnhphn sngca video (phn44)Cicngkhngngngcnhin,xtvllinquannthnh phn Y cho HVS (phn 32) Hnh 4 minh ha hai chui thi gian PSNR Php o khc m PSNR c th c s dng trong trng hp ny phn mm nh gi cht lng video mong mun phi thay th PSNR/MOS 1.4.6. Tnh ton MOS Do cc chui thi gian PSNR rt di nn PSNR ca mi khung n c nh x vo cc mc MOS trong bng 1 nh m t trong phn 32 n y ch cn li 5 mc v mi khung ca mtmc no c tnh iu ny c th d dng so snh vi phn s ca cc khung c phn loi t video bn gc nh minh ha trong hnh 5 Ct ngoi cng bn tay phi hin th cht lng ca video bn gc nh l mt tham kho, few losses c ngha l t l mt gi trung bnh l 5 cn ct ngoi cng bn tay tri cho thy cht lng video vi t l mt gi l 25 Hnh 5 minh ha cc truyn ti video ging nhau nh trong hnh 4 ee Pm X 20Lp 11KTTTKH

Hnh 5: V d v video c phn loi theo MOS (truyn dn video ging nh trong hnh 4) C th nhn thy c tc ng ca mng v hiu qu ca h thng mng c th c th hin da vo cht lng cm nhn ca ngi s dng Hnh 5 cho thy cht lng ca mt video no i gn vi cht lng video c th nhn c ti a 1.4.7. Nhm cng c th 3 cn thit Cc chng trnh c trnh by trn l c sn nh l m ngun ISO-C hoc nhng chng trnh trc khi bin dch cho Linux-i386 v Windows thc hin vic nh gi cht lng video ca mnh th bn cn cn mt s phn mm t cc ngun khc na Vic tch hp n vo c cu EvalVid c trnh by trong ti liu tham kho Nu bn mun nh gi cc h thng truyn ti video s dng h thng Unix hoc Windows th sau bn ln lt cn ti TCP-dump hoc win-dump n c th ly n t: - http://www.tcpdump.org- http://windump.polito.it n cng cn cc files video th (videos c m ha khng b tn tht) v b m ha v b gii m (c kh nng gii m cc lung video b hng) codec MPEG-4 c sn c ly t ee Pm X 21Lp 11KTTTKH

- http://www.m4if.org/resources.php - http://mpeg.nist.gov/ 1.5. Cc kt qu lm mu cng c ny c s dng nh gi cht lng video cho nhiu m phng [1, 12] v cc php o [7]. N c chng minh c th s dng c v kh n nh Cc kt qu mu c cho thy y v c m t ngn gn Hnh 6 cho thy kt qu ca vic nh gi cht lng video vi EvalVid cho mt m phng cavictruyntivideoMPEG-4trnmtngkhngdyHnhnychobit phn trm cc khung vi 5 mc MOS, ct ngoi cng bn tay phi cho thy mc MOS ca video bn gc (khng c tn tht mng) R rng rng cch thc mu en ti hot ng khng tt v r rng rng cht lng video i vi hai cch thc khc tng ti ci ct tham kho vi cc deadlines tng Hnh 6: V d v |nh gi| cht lng video (mc MOS) vi EvalVid Tng t nh vy, hnh 7 cho thy tng ca cm nhn ngi s dng vi increasing dropping deadlines v cch thc tt hn cho mt m phng ca h thng OFDM im cm nhn ngi dng c tnh theo cc kt qu MOS thu c vi EvalVid Cc ct trong hnh ny cho thy tng s ngi s dng c th c cung cp vi MOS ee Pm X 22Lp 11KTTTKH

Hnh 7: V d v vic |nh gi cht lng video (s ca ngi s dng c tha mn) vi EvalVid 1.6. t lun v cc ch cho vic nghin cu sau ny C cu EvalVid c th c dng nh gi hiu sut ca vic ci t mng hocccmphngnhvocmnhnngisdngHnna,victnhton tr, jitter, v tn tht cc gi, khung c thc hin cng c hin ny h tr cc ng dng lung video chun MPEG-4 nhng n c th d dng c m rng h trccbcodecsvideokhchocthmchccngdngkhcnhlungthoi chnghnCctnhcnhtnhcabgiimvideothngthng(xabcc khungbmt)lmchonkhngthnhgichtlngckhcphcPhp nh gi cht lng video da vo PSNR c gii thiu, cng thun tin hn c bitchoccchuivideodihnldavoPSNRtrungbnhcngcc thc hin trong ISO-C cho tnh di ng tia v c thit ktheomodule d dngmrngviccngdngkhcNcthnghimthnhcngvi Windows, Linux v Mac OS X. CccngccaccuEvalVidcmrnglintchtrccb codecsvideokhcnhH263,H26LvH264vhtrthemccchcnng codec nh FGS v ng b li khung bn trong Hn na, s h tr ca chin lc b m ti to ng l mt ch ca cc nghin cu sau ny Ngoi ra, n c ln k hoch h tr thm cc ng dng khc v d, thoi qua IP (VoIP) v lung audio-videocngbCuicngnhngkhngkmquantrngccphpo khc hn l da vo PSNR s c tch hp vo c cu EvalVid. ee Pm X 23Lp 11KTTTKH

II. Assignment Fileyuvsdnglmother-daughter_cif.yuvcdownloadttrangweb http://trace.eas.asu.edu/yuv/index.htmlDung lng 44550 K 2.1. M ha Mhamother-daughter_cif.yuvthnhfilemother-daughter.mp4sdng codec mpeg4, dng cng c ffmpeg#ffmpegscifimother-daughter_cif.yuvr25vcodecmpeg4mother-daughter_cif.mp4Hnhnhcapturecafilemother-daughtermp4cplaybngphnmm Windows Media Player. File mother-daughter_cif.mp4 c dung lng 450KB ee Pm X 24Lp 11KTTTKH

ee Pm X 25Lp 11KTTTKH

-Nhn xt: So snh hai file khi chy ta thy cht lng hnh nh theo di bng mt thng khng khc nhau nhiu lm tuy nhin dung lng file gim xung rt nhiu T l nn ca video y l:

Nhvy,vicmhagipchodunglngfilecgimxungrtnhiu trong khi cht lng video m ha vn chp nhn c Ty theo cc tham s s dng khi m ha chng ta s c c cc file videom ha vi cc t l nn v cht lng khc nhau. 2.2. ii mGiim filemother-daughter_cif.mp4s dng ffmpeg ta c file video th c ti to mother-daughter_cif_decoded.yuv # ffmpeg i mother-daughter_cif.mp4 mother-daughter_cif_decoded.yuv S dng cng c psnr trong Evalvid o PSNR# psnr 352 288 420mother-daughter_cif.yuv mother-daughter_cif_decoded.yuv > psnr.txt Gi tr PSNR trong file psnr.txtsau c tng hp li cho bng sau: ee Pm X 26Lp 11KTTTKH

CopyccgitrnyvotrongExcelvtinhnhvthtacthktqu PSNR nh sau:

-Nhn xt: Trng hp ny ch o PSNR gia video trc khi m v sau khi gii mnntachnhgichiunngcabmhavgiimchkhng nhgichiuqutruyndnDokhngchintngmtgi,motn hiu do vn truyn dn gy ra nn gi tr PSNR trong trng hp ny kh cao (trung bnh khong 39-40) v iu chng t b m ha v gii m hot ng kh tt 2.3. hit lp mng v truyn file Thit lp mt mng Adhoc gia 2 my My 1: Sender (169.253.253.79) My 2: Client(169.253.253.70) -Sdngfilevideothmother-daughter_cif.yuvtrnlmuvochob m ha Dng b codec x264 m ha mother-daughter_cif.yuv # x264 -I 30 -B 64 --fps 30 o mother-daughter_cif.264 --input-res 352x288 mother-daughter_cif.yuv Dng MP4ox to file ng gi dng mp4 v hint track# MP4Box -hint -mtu 1024 -fps 30 -add mother-daughter_cif.264 mother-daughter_cifx.mp4 S dng Java truyn file gia hai my 05101520253035404550110192837465564738291100109118127136145154163172181190199208217226235244253262271280289298Axis Title Chart Title Series1 ee Pm X 27Lp 11KTTTKH

Saukhithucfilemother-daughter_cifx.mp4timyClientTimynytakhi phc li video bng cch gii m a v file yuv - Gii m video nhn c pha nhn (s dng ffmpeg) #ffmpeg i mother-daughter_cifx.mp4 mother-daughter_re.yuv - o PSNR gia file video th va gii m c vi file video th ban u # psnr 352 288 420 mother-daughter_cif.yuv mother_re.yuv > psnr.txt Gi tr PSNR trong file psnr.txtsau c tng hp li cho bng sau: Cc gi tr ny c v ra th nh sau: ee Pm X 28Lp 11KTTTKH

-Nhnxt:TrnghpnychoPSNRgiavideotrckhimvsaukhi truynnn ta ch nh gi c hiu nng ca b m ha v gii m v nh gi c hiu qu truyn dn Quan st th ta thy lc nhng gi tin u cht lngPSNRkhngcaoQuanstvideothucthcngchotathycht lng video khng cn c nhng ban u 051015202530354011223344556677889100111122133144155166177188199210221232243254265276287298Series1 ee Pm X 29Lp 11KTTTKH

L M O [1]A.C.C.Aguiar,C.Hoene,J.Klaue,H.Karl,A.Wolisz,andH.Miesmer. Channel-awareschedulersforvoipandmpeg-4basedonchannelprediction.tobe published at MoMuC, 2003. [2] Johan Berts and Anders Persson. Objective and subjective quality assessment of compresseddigitalvideosequencesMastersthesis,ChalmersUniversityof Technology, 1998. [3] ITU-R Recommendation BT.500-10. Methodology for the subjective assessment of the quality of television pictures, March 2000. [4]SarnoffCorporation.Jndmetrix-iqsoftwareandjnd:Ahumanvisionsystem model for objective picture quality measurements, 2002. [5] Project P905-PF EURESCOM. Aquavit - assessment of quality for audio-visual signals over internet and umts, 2000. [6]LajosHanzo,PeterJ.Cherriman,andJuergenStreit.WirelessVideo Communications.Digital & Mobile Communications. IEEE Press, 445 Hoes Lane, Piscataway, 2001. [7] Daniel Hertrich. Mpeg4 video transmission in wireless lans basic qos support on the data link layer of 802.11b. Minor Thesis, 2002. [8] H.Sanneck,W.Mohr, L.Le,C.Hoene, and A.Wolisz. Quality of service support forvoiceoveripoverwireless.WirelessIPandBuildingtheMobileInternet, December 2002. [9] ISO-IEC/JTC1/SC29/WG11. Evaluation methods and procedures for july mpeg-4 tests, 1996. [10]ISO-IEC/JTC1/SC29/WG11.ISO/IEC14496:Informationtechnology- Coding of audiovisual objects, 2001. [11] J. Klaue. Evalvid http://www.tkn.tu-berlin.de/research/evalvid/fw.html. [12]J.Klaue,J.Gross,H.Karl,andA.Wolisz.Semantic-awarelinklayer schedulingofmpeg-4videostreamsinwirelesssystems.InProc.ofApplications and Services in Wireless Networks (AWSN), Bern, Switzerland, July 2003. [13] Weiping Li. Overview of fine granularity scalability in mpeg-4 video standard. IEEE transaction on circuits and systems for video technology, March 2001. ee Pm X 30Lp 11KTTTKH

[14]Jens-RainerOhm.Bildsignalverarbeitungfuermultimedia-systeme.Skript, 1999. [15]ITU-TRecommendationsP.910P.920P.930.Subjectivevideoquality assessmentmethodsformultimediaapplications,interactivetestmethodsfor audiovisual communications, principles of a reference impairment system for video, 1996. [16]MartynJ.RileyandIainE.G.Richardson.DigitalVideoCommunications. Artech House, 685 Canton Street, Norwood, 1997. [17]CormacJ.Sreeman,Jyh-ChengChen,PrathimaAgrawal,andB.Narendran. Delayreductiontechniquesforplayoutbuffering.IEEETransactionson Multimedia, 2(2):100112, June 2000. [18]ANSIT1.801.01/02-1996.Digitaltransportofvideoteleconferencing/video telephony signals. ANSI, 1996. [19] ANSI T1.801.03-1996. Digital transport of one-way video signals - parameters for objective performance assessment. ANSI, 1996. [20]StephenWolfandMargaretPinson.Videoqualitymeasurementtechniques. Technical Report 02-392, U.S. Department of Commerce, NTIA, June 2002.