Muaj ntau ntau yam ntawm hard disk video recorders ntawm lub khw. Yuav ua li cas xaiv qhov zoo tshaj plaws hard disk video recorder yog ib qho teeb meem nyuaj rau ntau tus neeg siv, tshwj xeeb tshaj yog cov novice, thiab nws yog tsis yooj yim sua kom pib. Thaum xaiv lub hard disk video recorder, peb yuav tsum tsom mus rau kev tshuaj xyuas cov duab compression txoj kev ntawm hard disk video recorder, daim duab duab zoo, real-time, network kev ua tau zoo, stability, tom qab-muag kev pab cuam thiab nqi.
Lub khoos phis tawj muaj hom hard disk video recorder (PC-BASEDDVR) siv lub khoos phis tawj ua haujlwm raws li cov khoom siv yooj yim, WINDOWS operating system ua cov software yooj yim, thiab tau nruab nrog video thiab audio compression boards. Nrog kev pab los ntawm cov kws tshaj lij compression algorithms thiab PC software thiab kho vajtse muaj peev xwm, kev saib xyuas cov yeeb yaj kiab thiab lub suab teeb liab tau pom. Ib tug ntaus ntawv rau kaw thiab playback. Cov cuab yeej tseem ceeb ntawm kev tswj hwm kev lag luam DVR yog daim npav video thiab audio compression. Compression method thiab duab zoo Compression technology yog lub hauv paus ntawm hard disk video recorder, thiab nws yog ib qho tseem ceeb tshaj plaws los xaiv txoj kev compression. Ntawm no, tsis yog tsuas yog cov duab zoo xwb, tab sis kuj tseem muaj peev xwm khaws cia thiab kev sib kis ceev ntawm cov duab yuav tsum tau txiav txim siab. Tam sim no, cov txheej txheem compression ntawm hard disk video phaib ntawm kev ua lag luam feem ntau suav nrog M-JPE, wavelet algorithm, MPEG-1, H263, MPEG-4, H.264 thiab lwm yam. 1) M-JPEG (peb tuaj yeem xav tias nws yog tus qauv rau kev saib xyuas compression) (ntau tus naj npawb ntawm cov koob yees duab hauv tsev thiab txawv teb chaws thiab cov video servers tau txais MJPEG compression technology txij li xyoo 1995, xws li SNC-Z2OP network lub koob yees duab tau tsim los ntawm SONY , AXIS2130PTZ network koob yees duab thiab lwm yam JPEG cov kws tshaj lij pab pawg, thiab nws cov duab hom yog rau txhua tus ncej, compression feem ntau yog compression piv ntawm 6: 1. Ib yam li txhua tus ncej yog cov duab ywj pheej, chav tsev ntawm MJPEG cov duab ntws yog JPEG duab ntawm ib ncej thiab ib lub thav duab Vim hais tias txhua lub thav duab tuaj yeem nkag mus rau qhov tsis txaus ntseeg, MJPEG Feem ntau siv hauv kev kho cov duab video. Motion JPEG tuaj yeem tsim cov yeeb yaj kiab zoo, puv npo, puv suab, tab sis nws yuav tsum tau kho vajtse ntxiv. Ntxiv mus, txij li MJPEG tsis yog hom qauv, cwb ma nufacturer muaj nws tus kheej version ntawm MJPEG. Cov ntaub ntawv ntawm ob sab tsis tuaj yeem paub ib leeg. Yog li MJPEG tau pib ploj mus ntawm qhov chaw ua yeeb yaj kiab.
Qhov zoo ntawm cov khoos phis tawj muaj MJPEG yog tias daim duab zoo yog qhov tseeb, tab sis qhov tsis zoo yog qhov compression tus nqi qis thiab bandwidth loj. Feem ntau, ib qho channel nyob ntawm qhov bandwidth ntawm 2M txog 3M. Thiab thaum lub ntim ua haujlwm loj heev, qhov chaw ua haujlwm video yuav tsis tuaj yeem ua tiav cov ntaub ntawv video ntau dhau, uas yuav ua rau cov ntaub ntawv sib txuas loj loj thiab ua rau muaj kev sib tsoo hauv lub network. Txij li thaum compression yog me me, cov ntaub ntawv khaws cia muaj peev xwm ntawm cov neeg rau zaub mov cia yuav yog qhov teeb meem. Ntawm 100MB network, 16 channels tsis tuaj yeem xa mus rau lub sijhawm tiag tiag ntawm tib lub sijhawm, thiab cov ntaub ntawv video ib teev yog ntau dua 500MB. Qhov teeb meem no yog ib qho teeb meem loj dua rau cov khoom siv network. Ntxiv mus, Motion-JPEG compression tshuab tsis txhawb lub suab thiab video synchronization, yog li txawm tias qee lub tuam txhab tau tsim lub suab, qhov teeb meem uas suab thiab yees duab tsis tuaj yeem synchronized nquag tshwm sim. Ntau yam khoom thaum ntxov hauv Taiwan thiab Kaus Lim Kauslim kuj tau siv txoj kev compression no, tab sis nws tau maj mam dhau los ntawm kev ua lag luam. 2) WaveletTransform (txhim kho txij li xyoo 1997) Wavelet hloov pauv kuj yog ib qho kev siv tshuab compression intra-frame. Txij li txoj kev compression no tshem tawm cov khoom siv ntau zaus ntawm cov duab, tsuas yog ib daim duab duab teeb liab tau khaws cia, uas yog tshwj xeeb tshaj yog haum rau lub sijhawm uas lub vijtsam hloov ntau zaus, thiab qhov sib piv compression kuj tau txhim kho rau qee yam, yog li nws kuj tseem siv los ntawm qee lub koob yees duab network, xws li NetCam-4 series ntawm cov koob yees duab network digital launched los ntawm BOSCH. Txawm li cas los xij, tag nrho cov ntaub ntawv compressed ntim tsis tau hloov ntau, thiab cov duab zoo tau txo qis. 3) H.263 (tiam thib ob) (txhim kho txij li xyoo 1998) H.263 yog tus qauv uas paub tab, thiab H.263 video coding txuj yog tus qauv qis-ntsis duab compression qauv tsim rau nruab nrab thiab zoo txav duab compression . H.263 txais yuav ib txoj kev coding ib txwm nyob rau hauv cov lus tsa suab video coding, thiab faib cov txheej txheem coding ua ob ntu: intra-frame coding thiab inter-frame coding. Kev txhim kho DCT hloov thiab quantization yog siv nyob rau hauv lub thav duab, thiab 1/2 pixel suab vector kwv yees nyiaj them nyiaj siv tshuab yog siv nyob rau hauv lub thav duab los ua kom cov lus tsa suab zoo dua. kom tau qhov kawg coding coefficients.
