Thaum yees duab, duab, lossis suab paj nruag tau txais kev cawmdim hauv hom digital, qhov tshwm sim tuaj yeem yog cov ntaub ntawv loj heev uas nyuaj rau kwj thiab siv ntau lub cim xeeb ntawm lub computer lossis hard drive uas nws tau txais kev cawmdim. Yog li ntawd, cov ntaub ntawv yog compressed los yog ua me me los ntawm kev tshem tawm ib co ntawm cov ntaub ntawv. Qhov no hu ua "lossy" compression.
Qhov cuam tshuam ntawm Compression
Feem ntau, kev suav cov txheej txheem (algorithm) yog siv kom cov txiaj ntsig ntawm cov ntaub ntawv ploj yog qhov tsis pom ntawm qhov muag liab qab hauv vis dis aus thiab duab lossis tsis tuaj yeem hnov suab paj nruag. Qee cov ntaub ntawv uas ploj lawm coj kom zoo dua ntawm tib neeg lub qhov muag tsis muaj peev xwm txheeb xyuas cov xim sib txawv me ntsis.
Hauv lwm lo lus, nrog cov cuab yeej compression zoo, koj yuav tsum tsis txhob pom qhov poob ntawm daim duab lossis lub suab zoo. Tab sis, yog tias koj yuav tsum tau ntim cov ntaub ntawv kom nws me dua nws cov hom qub, qhov tshwm sim yuav tsis pom. Nws tuaj yeem ua rau daim duab zoo heev uas cov yeeb yaj kiab tsis tuaj yeem saib lossis lub suab paj nruag yog tiaj thiab tsis muaj sia.
Ib zaj yeeb yaj kiab siab tuaj yeem nqa tau ntau lub cim xeeb, qee zaum ob peb gigabytes. Yog tias koj xav ua yeeb yaj kiab ntawd ntawm lub xov tooj smartphone, koj yuav tsum ua kom nws ua cov ntaub ntawv me me, lossis nws yuav siv tag nrho lub xov tooj nco. Qhov poob ntawm cov ntaub ntawv los ntawm qhov siab compression tsis pom ntawm plaub-nti npo.
Tab sis, yog tias koj tso cov ntaub ntawv ntawd mus rau Apple TV, Roku Box, lossis cov cuab yeej zoo sib xws txuas nrog lub vijtsam loj TV, qhov compression yuav pom tseeb, thiab nws ua rau cov yeeb yaj kiab zoo li txaus ntshai thiab nyuaj rau saib. Cov xim yuav zoo li blocky, tsis du. Ntug tuaj yeem plooj thiab jagged. Cov kev txav tuaj yeem ua rau plooj lossis ua tsis taus pa.
Qhov no yog qhov teeb meem nrog kev siv AirPlay los ntawm iPhone lossis iPad. AirPlay tsis kwj los ntawm qhov chaw. Hloov chaw, nws ntws cov playback rau hauv xov tooj. Cov kev siv zog pib ntawm AirPlay feem ntau tau raug tsim txom los ntawm cov yeeb yaj kiab siab compression.
Kev Txiav Txim Siab Zoo vs. Txuag Chaw
Thaum koj yuav tsum xav txog qhov loj ntawm cov ntaub ntawv, koj yuav tsum sib npaug nrog kev tswj xyuas cov suab paj nruag, duab, lossis yees duab zoo. Koj lub hard drive lossis media server qhov chaw yuav raug txwv, tab sis cov hard drive sab nraud tau txo qis rau tus nqi kom muaj peev xwm loj dua. Qhov kev xaiv yuav yog qhov ntau thiab qhov zoo. Koj tuaj yeem tau txais ntau txhiab cov ntaub ntawv compressed ntawm 500 GB hard drive, tab sis koj xav kom muaj ntau pua cov ntaub ntawv zoo xwb.
feem ntau koj tuaj yeem teeb tsa qhov kev nyiam rau ntau npaum li cas cov ntaub ntawv xa tuaj lossis khaws cia yog compressed. Cov chaw hauv cov kev pab cuam suab paj nruag zoo li iTunes tso cai rau koj los teeb tsa tus nqi compression rau cov nkauj uas koj import. Suab paj nruag purists pom zoo kom siab tshaj plaws, yog li koj tsis poob ib qho ntawm cov subtleties ntawm cov nkauj, 256 kbps rau lub tso suab ntawm qhov tsawg kawg nkaus. HiRes audio formats tso cai rau tus nqi siab dua. Yees duab JPEG teeb tsa yuav tsum tau teem rau qhov loj tshaj plaws kom tswj tau cov duab zoo. Cov yeeb yaj kiab siab txhais yuav tsum tau tshaj tawm hauv lawv cov hom ntawv digital uas tau khaws tseg thaum xub thawj xws li h.264 lossis MPEG-4.
Lub hom phiaj ntawm compression yog kom tau cov ntaub ntawv me tshaj plaws yam tsis muaj cov duab lossis cov ntaub ntawv suab tsis pom. Koj tsis tuaj yeem yuam kev nrog cov ntaub ntawv loj dua thiab compression tsawg dua tshwj tsis yog tias koj khiav tawm ntawm qhov chaw.
