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7/30/2019 Cc tiu chun nn

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Cc tiu chun nn

Sv: Cao vnhipDT1 K4


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Chun nn MPEG

I: chun nn MPEG

+ khi qut v MPEG

+ MPEG - 1+ MPEG - 2

+ MPEG - 4

+ MPEG - 7


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Khi qut v MPEGChun nn MPEG (Moving Picture Expert Group) lchui cc chun nn video vi mc ch l m ho tn

hiu hnh nh v m thanh tc t 1,5

50Mbit/s. Nn d liu audio vi t l t 5:1 10:1.

+ MPEG - 1: nn nh ng c kch thc 320 x 240, tc bitcn t 1 Mbit/s n 1,5 Mbi/s dng cho ghi hnh trn bng t

v a quang (CD), ng thi truyn dn trong cc mng.+ MPEG - 2: c s dng cho cc ng dng cao hn vi tc

cn 10Mbit/s, truyn tn hiu truyn hnh s thngthng.

+ MPEG - 3: nn tn hiu s xung cn 50 Mbit/s truyn

tn hiu truyn hnh c phn gii cao.+ MPEG - 4: dng cho nn hnh nh video vi t khung hnh

v yu cu lm ti chm. Tc d liu yu cu l 940Kbit/s. MPEG - 4 pht trin cc tiu chun m ho i vitc bit rt thp.

+ MPEG - 7: m t thng lin ca rt nhiu loi phng tin, chophp kh nng tm kim nhanh v hiu qu theo yu cu


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Cc cu trc nhloi I (In tra Picture): l nh c m ho ring, tng t

nh vic m ho nh tnh trong JPEG. nh I chang d liu ti to li ton b hnh nh v chophp truy cp ngu nhin. Tuy nhin t t l nnthp nht.

loi P (Predicted pictre): l nh c m ho c bchuyn ng t cc nh I hoc P pha trc (nhd on trc). nh P cho t s nn cao hn nh I, cth lm mt nh so snh cho vic b chuyn ng

cc nh P v B khc.loi B (Bi Directional Predicted Pictutre): l anh cm ho s dng b chuyn ng t cc nh I hoc P pha trc v pha sau (nh d on hai chiu).


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nh B cho t l nn cao nht v c nhiu u im:- Gii quyt c cc vn thay i nh cng

nh khng d bo c s thay i v ni dunghnh nh.- Vic s dng b chuyn ng t hai nh cho

t s tn hiu/tp m tt hn nu nh ch s dng

b chuyn ng t mt nh.- nh B khng s dng l nh so snh cho nh

khc nn n c th m ho vi s lng bit thp vkhng gy li tr trn ng truyn.

loi D (Dc-coded Pictre): l nh c s ng trongMPEG - 1 v MPEG - 4 nhng khng c s dng MPEG -2. nh c cc thnh phn mt chiu ura DCT c th hin.


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Nhm nh (GOP)Vi chun MPEG, cht lng nh khng nhng phthuc vo t l nn trong tng khun hnh mcn ph thuc vo di ca nhm nh. Nhm

nh GOP (Group Of Pictre) mang thng tin clp ca MPEG. c mt khun hnh honchnh, nh P v B cn phi c d liu t ccnh ln cn. Mi nhm nh bt buc phi bt

u bng mt nh I hon chnh sau l ccnh P v B. Nhm nh c th m (Open) hocng (Close).


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nh P (nh 4) c d bo trc trn c s nh I (nhI). nh B c d on t hai hng, nh B (nh 2) v

nh B (nh 3) c d on t hai nh, nh I (nh I)v nh P (nh 4). nh B (nh 5) c d on t 2nh, nh P (nh 4) v nh I tip theo (nh 6). Tht truyn nh v hin nh trn mn hnh l khng

ging nhau.


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Cu trc dong bit MPEG


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Kin trc dong d liu MPEG


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Trong tiu chun nn MPEG-1 gim phc tp v githnh b gii m,th MPEG-1 c mt s tham s mc nhthnh hngs theobng:

Tiu chun nn MPEG-1

Tham s Gi trcci

rngnhChiu cao nhTcnhSlng MBGii vecter chuynngKch thcbmu voTc bt

768 im576 dng

30 nh/s396

+_ 64 im327.680 bit

1,8Mbps


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C php dng bt gm 6 lpsdngc hai dng nn:- nn intre:biniDCT,lngt ho,m ho VLC cho nh I- nn Inter c lng chuyn ng,to d bo c b chuyn

ng cho nh B v P.MPEG-1 c mtvi tiu chun sau:- Ch c cu trc lymu 4:2:0.- Kch thcnhtia 720x576 pixel- di muu vo 8 bit- Lngt ho DCT 9 bit- Lngt cho MB 16x16- di ccihs DC l 8 bit- Sdng khung P v B- chnh xc d bo chuynng l naim- Tc bt tia 1.85 mbps


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Hthngnn MPEG -1

Qu trnh m ho MPEG-1


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Qu trnhgii m

Qu trnh gii m MPEG-1


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MPEG-2 gm 4phn:

- p1:h thng(iso/iec 13818-1):xc nh cu trc ghp knhaudio,video cung cpngbthi gian thc

- p2:h thng(iso/iec 13828-2) xc nh nhng thnh phn mho idin cho dliu video v x l gii m khiphc.

- P3: audio(iso/iec 13818-3) m ho v gii m tn hiu mthanh

- p4: biu din(iso/iec 13818-3) nh ngha qu trnh kim tracc yu cuca MPEG-2.

So vi MPEG-1 th MPEG-2 c nhiu tinb v kch thcnh v tc phn giinh

Tiu chun nn MPEG-2


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Kh nng co gin v ng dng MPEG-2

Khnngco gin l khnnggii m c 1 phn dng bitMPEG-2 clpvi phn cn linhm khiphc video vichtlnghnch.c nhiuloi co gin nh sau:

+ co gin khng gian:dng bit co nhiulp video v c phngii khc nhau.

+ co gin SND:c nhiu lp video,c cng phn gii khnggian nhng SNR khc nhau

+ co gin thi gian:c phn giithi gian khc nhau

+ co gin phn chia s liu:chia lm 2 phn(u tin cao-h sDCT tnsthp:u tin thp-hs DCT tns cao)


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Phm vi ngdngca MPEG-2 rtln.n c 4 cp:

Level C khung

Low 352x288(1/4 ctivi chun)

Main 720x576(ctivi chun)

High-1440 1440x1152

High 960x576 hoc 1920x1152


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Nn MPEG-2 c chui cc mc (Level) v c tnh (Profile)c dng cho nhiu ng dng khc nhau. Phn chia cc cutrc thnh cc tp con gi l Profile. Trong phm vi mi Profile

ch cho php s dng cc phn t ca cc phn t va phitrong cu trc tn hiu y .


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Ghp knh audio-videostheo chun MPEG-2

Hthngtruyn tn hiu MPEG-2h thng MPEG-2 sdngcu trc d liudng gi nhgi liutrong mng truyn thng.cc gi d liu lun lun bao gmphnu(header) vphnti(pay load)


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Tiu chun nn MPEG-2

Cu trc dng bit video MPEG-2

Cu trc dng bit video MPEG-2 c s phn lp v l sm rng c php ca cu trc MPEG-L. N bao gm ccchc nng ca MPEG-L, c ngha l chng tng hp vinhau. C hai hng i trong dng bit MPEG-2, hoc theo

quy trnh ca MPEG-L hoc theo chc nng m rngca MPEG-2.


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MPEG-2 c kh nng x l chui video xen k. S mho c th thch nghi vi s la chn Field hoc Frametrong khi MPEG-L ch c mt mode c nh.

Chui video c bt u m ho bng Sequence Header,sau l chui m rng (nu c) v cc nhm nh. Nuphn chui m rng khng c xc nh (khng c mbo c thnh phn m rng), cc lp tn hiu tip theo khi s thc hin quy trnh ging MPEG-L, l tng hpthun.

Header ca nhm nh c chc nng tng t nh Headerca MPEG-L v khng c chc nng c bit trong

Extension Header ca GOP. Cc thng s quan trng dng m ho m rng c xc nh ngha trong ExtensionHeader ca nh.


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