Cov txheej txheem tsim rau kev sib tham video systems

Cov txheej txheem tsim rau kev sib tham video systems

Kev sib tham yees duab siv rau cov neeg hauv ob lossis ntau qhov chaw sib txawv. Nrog kev pab ntawm multimedia computer technology thiab kev sib txuas lus siv tshuab, audio, video thiab cov ntaub ntawv cov ntaub ntawv raug xa mus rau ib leeg los ntawm kev sib txuas network thiab cov khoom siv sib txig sib luag kom ua tau raws sij hawm sib tham sib tham. Cov cuab yeej siv los ua kom tiav lub hom phiaj ntawm lub rooj sib tham. Tam sim no hais tias video conferencing system tau los ua ib qho tseem ceeb ntawm txoj kev sib txuas lus thiab kev sib koom tes hauv lub tuam txhab, cov kev cai tseem ceeb rau kev sib tham video video yog dab tsi?

Ua ntej, bandwidth

Feem ntau, qhov ntau dua qhov bandwidth, cov dluab zoo tshaj thiab cov video teebmeem yuav pab tau. Piv txwv li, lub suab yees duab teeb meem loj tshaj plaws uas muaj peev xwm muab 720P, piv txwv tias cov ntaub ntawv ntim ntawm ib daim duab yees duab sawv cev ntawm 24 khoom, ces: 720P duab duab Thawj cov ntaub ntawv yog 1280 × 720 × 24/8/1024 = 2700 Kbyte. Yog hais tias tus duab txav yog 25 ntu ib pliag, qhov txwv cov ntaub ntawv tus nqi ntawm ob ntawm 720P tsiv duab yog 2700 KByte × 25 = 67500 KByte, thiab lub kwj xa txuas yog 67500 × 8 = 540 000 Kbit / S = 524 Mbps. Hauv daim ntawv thov cov ntaub ntawv, tus nqi ntawm cov ntaub ntawv yuav hloov ntawm 10% thiab 40% vim qhov tseeb tias qhov chaw tsis raug tsau. Tus nqi ntawm cov ntaub ntawv yog heev amazing.

Thib ob, compression technology

Muaj ib qho kev sib txuas ua kom zoo txaus tsis muaj peev xwm daws tau qhov teeb meem ntawm kev sib kis ntau dhau, thiab qhov muag tsis pom kev siab bandwidth yuav tsuas nce cov teeb meem nyuaj. Cov kev hloov compression algorithm nrog siab compression piv tau zoo txo cov nqi ntawm cov ntaub ntawv thiab ua video thiab cov ntaub ntawv. Hloov tau zoo ntawm IP network. Muaj ob qho yeeb yam ntawm kev txav cov duab: qhov sib haum xeeb thiab kev sib raug zoo ntawm lub cev, ob qho tib si uas yuav tsim kom muaj ntau ntau cov ntaub ntawv redundant hauv daim duab. Txheem zoo heev algorithms tau zoo tshem cov ntaub ntawv no rov qab. Piv txwv, nyob hauv ib lub yeeb yaj kiab video uas muaj suab nrov, cov duab cov cim suab yog siv H.264 tus qauv, thiab H.264 qhov sib txig sib luag yog siab li 80: 1 piv rau cov qauv siv. Piv txwv, hauv qhov piv txwv saum toj no, kwj deg ntawm 720 mus rau duab xa duab yog 524/80 = 6.55 Mbps.

Thib peb, tshuab thev naus laus zis

Multicast yog ntau qhov chaw tshaj tawm, thiab kev sib kis thiab kev txais tos yog ib qho-rau-ntau cov kev sib raug zoo. Thaum tus txheej txheem sib kis, tus neeg sender tsuas xav xa ib daim ntawv ceeb toom ib zaug xwb, thiab txhua tus neeg siv nyob rau hauv pawg pab neeg coob tuaj yeem koom tau cov ntaub ntawv pob ntawv. Nyob rau hauv video conferencing system daim ntawv thov, thaum lub teeb liab ntawm lub cev mus rau txhua qhov ntawm, seb nws yog rov qab taw tes-rau-taw kev sib txuas lus los yog tshaj tawm, lub network bandwidth yog khib nyiab, thiab cov ntaub ntawv kis tau ntawm cov tshuab raj multicast yog muab faib rau hauv lub network ntawm, uas txo cov nqi ntawm cov ntaub ntawv hauv lub network.

Qeb plaub, kev sib txuas lus kis kab mob

H.320 raws tu qauv (rau pawg sib tham ntawm ISDN, npaj thiab txais yuav hauv 1990, yog thawj tus qauv thoob ntiaj teb) raws li N-ISDN (Kev Nqis Cov Kev Pab Hauv Zos Network), muaj peev xwm sib tham thiab ua raws li cov kev hloov ntawm circuit, dav Siv hauv tes hauj lwm hauv circuit switched xws li VSAT / DDN / ISDN. Tus qauv H.320 suav nrog tus qauv H.200 thiab tus qauv T.120. H.200 cov qauv ntawm cov qauv raug tsom mus rau cov kev pabcuam audiovisual, tshwjxeeb cov kev sib txuas lus uas tsuas yog xa cov duab xa mus. Tus T.120 series ntawm cov qauv yog ib daim ntawv cog lus rau cov ntaub ntawv tshaj tawm hauv lub rooj sib tham hauv TV.

H.323 kev cai (lub rooj sib tham video hauv DVR, H.323, tau npaj tseg hauv Lub Peb Hlis Ntuj 1997, muab cov qauv kev sib txuas lus ntawm multimedia rau PBNs lub lag luam (xws li IP networks), thiab tam sim no yog qhov kev siv loj tshaj plaws. thiab cov txheej txheem muab kev sib txuas lus rau kev sib txuam ntawm ntau hom kev sib txuas nrog cov tes hauj lwm hauv IP, H.323 qhia txog plaub yam khoom: terminals, gateways, gatekeepers, thiab ntau yam tswj kev siv. qhov sib txuas lus ntawm cov suab paj nruag, video thiab cov ntaub ntawv Cov kev kho video video conferencing ua tau txais kev pom zoo rau cov qauv no, uas ua kom txhua tus neeg ua lag luam thiab cov MCUs sib txuas tau Ib feem ntawm qhov chaw tsim khoom siv tau zoo tshaj ob qho qauv, Thaum cov khoom siv cuab yeej siv H.323 tus qauv.

SIP raws tu qauv (cov ntaub ntawv raws li txheej txheem kev tswj cov txheej txheem, uas yog kev sib txuas lus ntawm IETE) yog ib daim ntawv thov rau hauv Internet rau audio thiab video sib txuas, uas ntxiv cov kev taw qhia thiab QoS cov kev cai, thiab coj los siv rau lwm cov qauv hauv Internet thiab cov txheej txheem. Xav, ua raws li cov ntsiab lus ntawm conciseness, kev loj hlob, compatibility thiab scalability, yog yooj yim kuj thiab yog txoj kev loj hlob ntawm kev sib tham video tom ntej.

V. QoS kev pabcuam kev khomob zoo

QoS yog qhov kev ruaj ntseg ntawm lub network thiab yog lub tshuab siv los daws cov teeb meem xws li kev ncua kev lag luam thiab kev sib thab. Yuav kom tau qhov tseeb ntawm txhua qhov chaw, qhov qeeb ntawm lub suab thiab yees duab yuav tsum tsawg dua 0.25S, thiab tus jitter yuav tsum tsawg dua 10ms ntawm qhov siab tshaj plaws. Tib lub sij hawm, yuav tsum tau ua raws li kev cim di ncauj. Yog ntev li qhov kev sib tw ua tiav thaum lub sij hawm, cov pob ntawv poob nqis yog tswj nyob rau hauv qhov ntau ntawm cov tib neeg tau txais, thiab muaj qee qhov kev sib kis raug cai, kom tag nrho cov ntaub ntawv hais txog lub vev xaib yuav raug coj los siv zoo.