Digital Video Broadcasting - Cable (DVB-C) kis tau tus mob rau digital cable TV, nrhiav tau nyob rau hauv Lub ob hlis ntuj 1994 nyob rau hauv lub European standard ETS 300 429. European Broadcasting Union (EBU) thiab European Telecommunications Standards Institute (ETSI). Xav txog dab tsi DVB-C yog, nws yuav tsum tau hais tias nws yog ib feem ntawm DVB tus qauv, uas txhais cov kev hloov kho ntawm MPEG-2 ntas nyob ntawm seb hom kev tshaj tawm.
keeb kwm ntawm tus qauv
Nws muaj ntau yam TV: satellite (DVB-S), cable (DVB-C) thiab VHF/UHF (DVB-T). Lub cim tshiab ntawm TV teeb liab yog raws li cov ntaub ntawv digital compression thiab xa mus. Qhov no muab cov duab zoo thiab kev siv bandwidth zoo dua li classic analog xim TV qauv xws li PAL, NTSC thiab SECAM.
Lub Ib Hlis Ntuj xyoo 1995, lub phiaj xwm DVB tau teeb tsa los ntawm EBU tau tshaj tawm cov txheej txheem uas txhais cov kev tshaj tawm digital tshiabqhov system. Txij li thaum xyoo 1996, DVB tau yog lub hauv paus kev siv rau kev siv digital TV xa mus rau EU hauv ntau lub tebchaws hauv ntiaj teb, suav nrog Russia. Teb Chaws Asmeskas muaj nws tus qauv HDTV terrestrial uas yog raws li MPEG-2, siv lub modem thiab ib lub encoder.
Kev saib xyuas tshwj xeeb hauv European kev faib tawm yog muab rau tus qauv cable. DVB-C yog dab tsi? Teb cov lus nug no, nws yuav tsum tau muab sau tseg tias niaj hnub DVB piav qhia txog kev xa xov ntawm digital TV ntawm satellite thiab cable. Nws npog cov qauv tsim thiab lub modem rau kev sib kis tau zoo tshaj plaws, nrog rau ntau yam ntxiv xws li teletext, cov lus qhia hauv hluav taws xob, thiab kev nkag mus tau raws li txoj cai. Lub kaw lus yog ISO MPEG-2 algorithm.
Building blocks
Kom nkag siab tias DVB-C yog dab tsi, kawm cov tswv yim theem pib. Daim duab thaiv ntawm DVB receiver muaj ib tug cable los yog ib tug kav hlau txais xov:
- Receiver - demodulation - kev kho yuam kev - ntxiv kev tswj xyuas thiab encryption module.
- MPEG demuxer.
- MPEG video decoder.
- MPEG audio data decoder.
- Interface.
- RGB / S-Video / PAL / PAL encoder.
- Ib lub computer lossis modem, thiab DVB-C uas muab kev ua haujlwm tau zoo.
- TV, VCR.
- Hi-Fi system.
Thawj tiam ntawm cov neeg siv khoom DVB receivers muaj lub thawv me me uas muaj lub receiver thiab saum MPEG decoder.
Cov neeg txais xov tooj muaj cov ntaub ntawv xa mus, cuam tshuam rau tus kheejcov khoos phis tawj thiab lwm cov xov xwm multimedia (EIA-232-E), ib lossis ntau dua ISO 7816 nti daim npav qhov, hom 2 PCMCIA connectors rau them nyiaj TV tswj module, thiab DVB-C hauv TV uas tuaj yeem muab kev sib txuas cable. Kev sib txuas ntxiv tuaj yeem suav nrog cov suab digital.
MPEG-2 encapsulation
Lub phiaj xwm DVB tsis tau txhais nws tus kheej cov duab encoding algorithm, tab sis tau xaiv qhov profile (subset) ntawm tus txheej txheem thoob ntiaj teb ISO/IEC 13818, feem ntau hu ua MPEG-2 hauv ETR 154. MPEG-2 yog ib qho audio/video compression algorithm optimized rau tshaj tawm zoo mus txog HDTV tus qauv raws li discrete cosine transform thiab motion kwv yees. Rau qhov project DVB, MPEG-2 lub ntsiab profile tau xaiv nyob rau theem tseem ceeb nrog cov ntaub ntawv siab tshaj plaws ntawm 15 Mbps.
theem tseem ceeb txhais tau hais tias mus txog 720x567 pixels ntawm 25Hz (TV zaus tus qauv siv hauv Tebchaws Europe) lossis mus txog 720x480 pixels ntawm 30Hz (siv hauv North America) nam piv tau txaus siab:
- 4:3.
- 16:9.
- 2, 21:1.
Main profile txhais tau hais tias kev txhawb nqa MPEG bidirectional, tab sis tsis siv SNR lossis kev daws teeb meem scalability.
Cov kev txwv tshwj xeeb tau raug xaiv hauv ETR 154 kom tau txais kev txhawb nqa los ntawm txhua tus neeg txais DVB.
Video:
- Npaj tus nqi 25Hz hauv zaj duab xis thiab teb tus nqi 50Hz hauv camcorder hom.
- Aspect ratio 4:3 thiab 16:9 (2, 21:1 yeem).
- Cov neeg txais yuav tsum txhawb nqa lub lauj kaub vectors,uas tso cai rau feem cuam tshuam tshaj plaws ntawm 16: 9 duab los tso tawm ntawm 4: 3 zaub hauv qhov tseeb qhov piv txwv.
- Image brightness daws teeb meem: 720 x 576, 544 x 567, 480 x 576, 352 x 576, 352 x 288.
Tus qauv MPEG-2 kuj txhais tau hais tias ISO/IEC13818-1 multiplexing system, uas tso cai rau ntau cov yeeb yaj kiab thiab suab sib xyaw ua ke. Hauv DVB, qhov no multiplexing method yog siv los tso cai rau ntau yam kev pab cuam los siv nrog bandwidth ntawm 38 Mbps.
Image processing
thawj cov yeeb yaj kiab raug tua hauv 4: 3 kev kawm hom. Cov qauv TV thaum ntxov tau txais nws, tuav cov yeeb yaj kiab sib raug zoo. Thaum cov neeg tsim yeeb yaj kiab hloov mus rau ntau hom ntawv (16: 9), TV hauv tsev kuj tau txais qhov kev tsim kho tshiab no los qhia qhov zoo ntawm qhov chaw. Tsis ntev los no, cov yeeb yaj kiab tau tso tawm ntau dua 2.21 hom: 1.
Yog tias daim duab 16: 9 yuav tsum tau tso tawm ntawm 4: 3 lub tsev ua yeeb yam hauv tsev, muaj ob txoj hauv kev siv los kho qhov sib piv ntawm daim duab - panning thiab scanning.
Pan & scan txhais tau hais tias DVB-T T2 C ntawm cov txheej txheem zoo li no yuav tso tawm txhua ntu ntawm cov yeeb yaj kiab hauv kev faib ua feem rau 4: 3=12: 9 piv, thiab 16: 9 duab qhov rai yuav tshwm nrog ib sab me me ntawm 9. Qhov seem 25% daim duab yuav raug txiav.
DVB-T Terrestrial transmission
kom nkag siab tias DVB T / C yog dab tsi, koj yuav tsum tauxav txog cov khoom ntawm cov kab ke hauv av, xws li qhov sib txawv ntawm cov teeb liab-rau-lub suab sib txawv nyob ntawm qhov loj multipath cuam tshuam thiab kev xav los ntawm cov phab ntsa hauv tsev. Lawv attenuate tej zaus, tsim congestrum spectrum, nrog rau kev cuam tshuam los ntawm cov nyob ze analog TV channels thiab los ntawm cov chaw nyob deb deb nyob rau hauv tib lub band.
Tus xaiv DVB-T modulation scheme muaj cov yam ntxwv hauv qab no:
- OFDM (Orthogonal Frequency Control Multiplex). Hauv cov qauv no, Fourier hloov pauv yog siv los tsim cov teeb liab tshaj tawm nrog ntau txhiab ntawm kev sib koom ua ke orthogonal modulated QAMs. Ib tug cim nqa ob peb kilobits ntawm cov ntaub ntawv. Lub sijhawm tiv thaiv tso cai rau lub ncha mus dhau ua ntej tus neeg txais khoom pom cov cim tom ntej - 8192 lossis 2048 tus neeg nqa khoom.
- Kev ruaj ntseg ntawm cov qauv kev hloov pauv tawm tsam ncha.
- Kev nthuav tawm ntau txoj kab ntau dhau ua rau kev siv ntau zaus spectrum zoo dua ntawm kev nyab xeeb ntawm cov khoom xa tawm ua haujlwm ntawm tib zaus.
Cable system transmitter
Digital Video Broadcasting (DVB) yog cov txheej txheem ntawm kev lees paub qhib TV. Lub teeb liab tawm tswv yim ntawm DVB-C transmitter yog nthuav tawm raws li cov kab ke ntawm cov pob ntawv nrog tus qauv MPEG thauj kwj. Txhua pob ntawv muaj 288 bytes. Thaum xub thawj nws yog scrambling kom dissipate zog. Tom ntej no, lub pob synchronization yog hloov. Tom qab ntawd, nws dhau los ntawm tus encoder. 16 bytes ntxiv rau kev tiv thaiv. Ib pob ntawv ntev dhau los ua 304 bytes.
Yuav kom nkag siab DVB-T2 C S2, nws yog dab tsi hauv kev xa tawm, xav txog kev ua haujlwm ntawm pob ntawv. Cov pob ntawv hloov kho dhau los ntawm 12-depth convolutional interleaver ua raws li daim duab qhia. Nws hloov cov pob ntawv bytes rau hauv 2D QAM cov cim nrog kuv thiab Q cov khoom.
Ob qhov tseem ceeb tshaj plaws ntawm txhua lub cim yog tom qab ntawd sib txawv ntawm qhov sib txawv kom tshem tawm qhov tsis meej pem qhia los ntawm QAM kev hloov kho. DVB-C txhawb ntau hom QAM: 16-QAM, 32-QAM, 64-QAM, 128-QAM thiab 256-QAM.
DVB-C receiver
Tus txais yuav ua qhov sib txawv ntawm kev ua haujlwm. Baseband RF teeb liab yog qib-kho, downconverted, thiab demodulated. Rau qhov kawg nkaus, cov cab kuj thiab lub sij hawm synchronization yog ua. Lub teeb liab ces dhau los ntawm kev sib tw lim. Hauv cov kab hluav taws xob, cov lus teb zaus ntawm cov channel tsis sib xws thiab tuaj yeem piav qhia raws li cov lim dej tawm. Yog li ntawd, lub teeb liab demodulated, sawv cev raws li ib theem ntawm ob-dimensional cim, yog kho siv ib tug equalizer.
Ob qhov tseem ceeb tshaj plaws ntawm txhua tus cwj pwm raug txiav txim siab hauv qhov sib txawv decoder. Cov cim ntawm lub teeb liab yog ces mapped mus rau ib theem ntawm bytes uas dhau los ntawm lub deinterleaver. Qhov no yog ua raws li kev txiav txim siab thiab kho qhov yuam kev, thiab tom qab ntawd descrambling. Tom ntej no, cov sync bytes raug hloov. Cov zis yog txheem MPEG thauj kwj.
C- kis tau tus mob specifications
Qhov noDVB system siv los faib cov TV digital hla cov xov tooj cua. DVB-C siv tib txoj kev (8 MHz, 7 MHz lossis 6 MHz) uas tau siv los faib cov qub analog TV. Nws yog populated nrog cov ntaub ntawv ntim uas tuaj yeem nqa cov ntaub ntawv tsis muaj yees duab, suab, thiab MPEG-2. Ua li no, cov xov tooj digital TV tuaj yeem faib tawm yam tsis tas yuav tsum tso tseg kev faib tawm ntawm analogue TV.
DVB-C siv quadrature amplitude modulation (QAM) rau cov ntaub ntawv. Feem ntau 64-QAM yog siv, tab sis qis-qib kev hloov kho xws li 16-QAM thiab 32-QAM thiab qib siab dua cov qauv xws li 128-QAM thiab 256-QAM kuj tsim nyog. Lawv lub peev xwm nce nrog kev siv cov kev hloov kho qib siab dua. Hauv qhov no, cov ntaub ntawv yuav tiv taus suab nrov thiab cuam tshuam.
Ib qho 8 MHz channel tuaj yeem nqa tus nqi them ntawm 38.5 Mbps yog 64-QAM siv. Qhov no txaus rau 4-6 TV programs. DVB-C yog haum rau tag nrho 7 MHz thiab 8 MHz raws ntawm cable tes hauj lwm. Hauv tebchaws Yelemes, DVB-C feem ntau tsuas yog siv 8 MHz raws ntawm 230 MHz txog 862 MHz.
New standard
Cov TV niaj hnub muaj tus qauv TV tshiab. Txawm li cas los xij, tsis yog txhua tus neeg yuav khoom nkag siab txog cov yam ntxwv ntawm DVB T2 C. Nws yog dab tsi? Nws yog tus qauv rau cov teeb liab kis tau tus mob nyob rau hauv broadband cable TV systems. Tus qauv txhais cov txheej txheem ntawm lub cev, xws li kev tiv thaiv kev ua yuam kev, kev hloov kho, thiab cov txheej txheem qis dua, tsim nyog rau cov ntaub ntawv ntim.
Piv rauTus thawj ntawm DVB-C, uas yog Ameslikas standardized nyob rau hauv 1994, DVB-S2 muaj ib tug tseem ceeb kis tau tus mob kev ua tau zoo zoo xws li spectral efficiency thiab ua hauj lwm yooj yooj yim, hloov pauv bandwidth, txhim kho muaj peev xwm hloov mus rau nplooj siab channel.
DVB-C2 tau tsim kho raws li DVB lub tswv yim los siv cov thev naus laus zis niaj hnub thiab ntau yam ntawm lawv cov ntsiab lus uas tsis tau siv rau thawj tiam.
Tsev neeg ntawm DVB kis tau tus mob nyob rau hauv lub tiam thib ob qauv kev sib haum xeeb mus txog rau DVB-C2 (DVB-S2, DVB-T2). Kev sib xyaw ua ke PLP thiab Cov Ntaub Ntawv Slice multiplexing tswv yim txoj hauv kev yog ib qho piv txwv ntawm qhov tshiab no. Lawv xyuas kom meej tias DVB-C2 tsis yog tsuas yog ua tau raws li kev lag luam thiab kev xav tau ntawm European tus qauv, tab sis kuj muab cov kev daws teeb meem zoo rau kev yooj yim thiab kev sib kis tau zoo.
Kev sib piv ntawm kev hloov kho
Qhov sib txawv ntawm DVB-T, DVB-S, DVB-C thiab DVB-H systems. DVB stands rau Digital Video Broadcasting. Lub kaw lus txhawb nqa kev daws teeb meem siab dua thiab pab txhawb nqa bandwidth.
DVB-T:
- Daim ntawv luv luv ntawm kev tshaj tawm digital video - terrestrial.
- Txoj kev hloov pauv hloov pauv - coded OFDM.
- Xa MPEG uncompressed audio thiab video.
- Used data modulation schemes: QPSK, 16QAM, 64QAM.
- Siv lwm tus encoder RS (204, 188) thiab sab hauv convolution.
- Inner thiab outer interleaver haum.
- Siv zausVHF thiab UHF channels nrog 6 MHz, 7 MHz thiab 8 MHz bandwidth.
DVB-S:
- Daim ntawv luv luv ntawm digital video tshaj tawm yog satellite.
- Siv MPEG-2 rau digital compression thiab decompression.
- Suitable for C band as well as Ku band frequencies.
- Tus DBS digital receiver siv FEC txoj hauv kev kho qhov yuam kev.
- Muaj cov satellite tshwj xeeb tso rau lub hom phiaj no.
- LHCP thiab RHCP polarization hom yog siv rau kev sib kis.
- DVB-S feem ntau xav tau lub kav hlau txais xov me dua.
DVB-C:
- Daim ntawv luv ntawm cov yeeb yaj kiab digital yog tshaj tawm xov tooj cua.
- Siv MPEG-2 lossis MPEG-4 compression.
- Data modulation: 16 QAM lossis 256QAM.
- Siv RS encoder ua FEC.
- Lub interleaving module haum rau hauv Circuit Court.
- Lub teeb liab kis tau los ntawm coaxial lossis fiber optic cable los ntawm cov chaw muab kev pabcuam rau cov neeg siv khoom.
- A DVB-C hom uas tuaj yeem siv zaus ntawm 55.25 txog 403.25 MHz.
DVB-H:
- Daim ntawv luv luv ntawm digital video tshaj tawm - khoom siv nqa tau.
- Siv VHF, UHF thiab L band frequencies.
- Tej zaum muaj nrog DVB-T system.
- Nov yog ib qho ntawm cov qauv xov tooj ntawm tes TV.
Kev hloov pauv hauv av
DVB-T yog tus qauv xa tawm video hauv av tsim los ntawm DVB. Nws yog thawj zaug siv rau xyoo 1997. Txij thaum ntawd los, Australia, Europe, thaj chaw ntawm Asia, ntau qhov chaw ntawm Africa thiab Colombia tau siv nws hauv lawv cov xov xwm tshaj tawm thiab xov tooj cua. DVB-T2 yogqhov thib ob version ntawm tus qauv no, qhia hauv 2008.
Txhua tus cwj pwm uas tsim lub npe muaj lub ntsiab lus hauv DVB-T2:
- DVB yog lub npe ntawm lub koom haum lub luag haujlwm tsim cov qauv qhib digital TV.
- T - muab los ntawm cov qauv hauv av, sib txawv ntawm satellite (DVB-S), cable (DVB-C) thiab tshaj tawm hauv xov tooj (DVB-H).
- "2" yog tiam thib ob.
Lub hom phiaj ntawm DVB-T2 yog kom ua tiav TV tshaj tawm zoo dua, vim tias yav dhau los DVB-T tsis muaj bandwidth txaus kom tso cai rau cov ntsiab lus siab tshaj tawm.
Kev sib piv ntawm cov yam ntxwv ntawm DVB-T thiab DVB-T2.
| Device, txheej txheem | DVB-T | DVB-T2 |
| Input interface | TS Simple | Multiple TS and GSE |
| Modulation | OFDM | OFDM |
| Kev kho yuam kev (FEC) | 1/2, 2/3, 3/4, 5/6, 7/8 | LDPC + BCH1 / 2, 3/5, 2/3, 3/4, 4/5, 5/6, 6/7, 8/9 |
| Modulation scheme | QPSK, 16QAM, 64QAM | QPSK, 16QAM, 64QAM, 256QAM |
| Kev sib tw | 1/4, 1/8, 1/16, 1/32 | 1/4, 19/128, 1/8, 19/256, 1/16, 1/32, 1/128 |
| FFT size | 2k, 8k | 1K, 2K, 4K, 8K, 16K, 32K |
System compatibility
Txhua DVB kis tau tus mob yog tsim los rau siab tshaj plaws compatibility. Qhov no txhais tau hais tias lawv tuaj yeem siv cov blocks sib xws, xws li Reed Solomon decoder thiab interleaver, yog tias ib tus neeg txais kev txhawb nqa ntau yam kev sib kis xov xwm.
Nyob rau hauv ib txwm DVB-C cable system muaj 8 MHz channels, 15% dov tawm txhais los ntawm DVB-C. Theoretical siab tshaj tus cim tus nqi yog 6.96MB.
Saib cable TV hauv PC tam sim no yooj yim dua ua tsaug rau kev tsim cov PC TV tuners thiab TV software nrog DVB-T2 C. Nws yog dab tsi? Rau ntau tus neeg saib uas nkag siab txog cov khoom siv hluav taws xob, qhov no yog qhov tseeb ntawm daim duab ua haujlwm yooj yim. Cable TV tuners lossis TV phaib ua haujlwm ib yam li tus kav hlau txais xov TV.
Cov cuab yeej lees txais kev tshaj tawm TV tshaj tawm uas tau nyeem los ntawm lub khoos phis tawj los tsim kom muaj TV nyob. Txhawm rau nkag siab txog qhov kev txhawb nqa DVB-C yog dab tsi, xav txog cov txheej txheem yooj yim rau kev txuas mus rau PC:
- Txiav cov hlua hluav taws xob uas txuas rau sab nraub qaum ntawm lub khoos phis tawj ntawm lub qhov hluav taws xob. Unscrew lub screws nyob rau sab laug ntawm lub PC nrog ib tug screwdriver. Tshem tawm sab vaj huam sib luag.
- Nrhiav qhov txuas txuas txuas txuas txuas lossis txuas PCIe ntawm lub motherboard. Maj mam ntxig daim npav cable TV tuner rau hauv qhov. Ruaj ntseg txoj haujlwm no nrog lub hau ntswj.
- Kaw rooj plaubPC.
- Txuas lub suab thiab video cables muab nrog DVB-C PC tuner rau lub PC.
- Txuas ib kawg ntawm lub cable rau lub PC tuner lub thawv thiab ntsaws rau lwm qhov kawg rau hauv cov xim sib txuas rau sab nraub qaum ntawm lub computer.
- Muaj cov xim sib xws nrog ntau xim rosettes. Ntau tus tab tom sim xyuas seb qhov DVB-C digital tuner yog dab tsi. Qhov no tuaj yeem qhia meej hauv cov ntaub ntawv qhia txog kev txuas nrog tus qauv.
- Nruab cov tsav tsheb rau daim npav TV tuner.
- Nyem "Start" khawm ntawm PC los ntawm thawj txoj cai-nias "Kuv Lub Computer" thiab xaiv "Properties", "Device Manager" thiab tom qab ntawd nyem "Media Controller" los ntawm cov npe.
- Right click thiab xaiv "Install Driver".
- Ntxig lub installation disc muab nrog lub TV tuner, nruab qhov program thiab rov pib lub computer. Siv software saib cable TV hauv PC.
Kaum xyoo dhau los, tsis yog txhua tus neeg saib tau paub txog DVB-C tuner. Nws yog dab tsi, units tuaj yeem piav qhia. Niaj hnub no, niaj hnub TV hom tau pib siv dav, uas tso cai rau ntau cov channel hauv ib qho multiplex. Yog li ntawd, manufacturers ntawm niaj hnub ntse TVs txaus siab los qhia nws rau hauv lawv cov khoom siv. Cov kev hloov pauv yog qhov nyuaj thiab cuam tshuam rau ntau tog. Txawm li cas los xij, cov kws tshaj lij tau sau tseg tias kev hloov pauv mus rau T2 yuav tshwm sim ntxov li xyoo 2022.
