Uticaj DVI kabela na kvalitet slike na LCD-u

[dmr]

Autor SRV

@MaxB & dmr: koristite EDIT. I multiquote po potrebi.

Dok si ovo pisao ja bas bio na editu

[Visage]

Autor dmr

I da li je neko imao slicnih iskustava ili ima neki primjer sa neta gdje je objasnjeno ili uporedjeno vise razlicitih DVI kabela ili je receno da DVI kabel utice na kvalitet prikaza neka slobodno kaze . Ja nisam mogao nista naci o ovome googlajuci. THX!!!

Evo ti iz nekih boljih PCE vremena, jedna mega rasprava iz koje ces saznati najbolji odogovor

Kvaliteta slike

[dmr]

Autor Visage

Evo ti iz nekih boljih PCE vremena, jedna mega rasprava iz koje ces saznati najbolji odogovor

Kvaliteta slike

Da ovdje se vise govorilo da li razlicite kartice imaju razlicitu sliku, i zasto, kada se prikljuce preko DVI izlaza. Ali poucno u svakom slucaju! THX!!!

[SPLiFF]

Autor Visage

Evo ti iz nekih boljih PCE vremena, jedna mega rasprava iz koje ces saznati najbolji odogovor

Kvaliteta slike

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Ogromni respect, Visage. Stvarno je uzitak citati tvoje postove, no comment

[Darth Vader]

The Role of Cable and Connection Quality

Cable quality, in general, should not be a significant factor in the DVI/HDMI versus Component Video comparison, as long as the cables in question are of high quality. There are, however, ways in which cable quality issues can come into play.

Analog component video is an extremely robust signal type; we have had our customers run analog component, without any need for boosters, relays or other special equipment, up to 200 feet without any signal quality issues at all. However, at long lengths, cable quality can be a consideration--in particular, impedance needs to be strictly controlled to a tight tolerance (ideally, 75 +/- 1.5 ohms) to prevent problems with signal reflection which can cause ghosting or ringing.

DVI and HDMI, unfortunately, are not so robust. The problem here is the same as the virtue of analog component: tight control over impedance. When the professional video industry went to digital signals, it settled upon a standard--SDI, serial digital video--which was designed to be run in coaxial cables, where impedance can be controlled very tightly, and consequently, uncompressed, full-blown HD signals can be run hundreds of feet with no loss of information in SDI. For reasons known only to the designers of the DVI and HDMI standards, this very sound design principle was ignored; instead of coaxial cable, the DVI and HDMI signals are run balanced, through twisted-pair cable. The best twisted pair cables control impedance to about +/- 10%. When a digital signal is run through a cable, the edges of the bits (represented by sudden transitions in voltage) round off, and the rounding increases dramatically with distance. Meanwhile, poor control over impedance results in signal reflections--portions of the signal bounce off of the display end of the line, propagate back down the cable, and return, interfering with later information in the same bitstream. At some point, the data become unrecoverable, and with no error correction available, there's no way to restore the lost information.

DVI and HDMI connections, for this reason, are subject to the "digital cliff" phenomenon. Up to some length, a DVI or HDMI cable will perform just fine; the rounding and reflections will not compromise the ability of the display device to reconstruct the original bitstream, and no information will be lost. As we make the cable longer and longer, the difficulty of reconstructing the bitstream increases. At some point, unrecoverable bit errors start to occur; these are colloquially described in the home theater community as "sparklies," because the bit errors manifest themselves as pixel dropouts which make the image sparkle. If we make the cable just a bit longer, so much information is lost that the display becomes unable to reconstitute enough information to even render an image; the bitstream has fallen off the digital cliff, so called because of the abruptness of the failure. A cable design that works perfectly at 20 feet may get "sparkly" at 25, and stop working entirely at 30.

In practice, it's very hard to say when a DVI or HDMI signal will fail. We have found well-made DVI and HDMI cables to be quite reliable up to 50 feet. But because the ability to reconstitute the bitstream varies depending on the quality of the circuitry in the source and display devices, it's not uncommon for a cable to work fine at 30, 40, or 50 feet on one source/display combination, and not work at all on another.

[dmr]

Da samo mi nije jasno kada se u tekstu kaze "because the bit errors manifest themselves as pixel dropouts which make the image sparkle" da li se misli da se u slici pojave iskrice ili da slika postane bljestavija? Ako je ovo drugo onda to definitivno primjetim sa origi. samsungovim kabelom.

[MaxB]

Autor dmr

Da samo mi nije jasno kada se u tekstu kaze "because the bit errors manifest themselves as pixel dropouts which make the image sparkle" da li se misli da se u slici pojave iskrice ili da slika postane bljestavija? Ako je ovo drugo onda to definitivno primjetim sa origi. samsungovim kabelom.

To sad i mene muci... Stvar je takva da ne znam kako je zakodiran DVI signal - ako je to jednostavno stream 0 i 1, odnosno obican stream piksela, i ravnomjerno po cijelom streamu se tu i tamo 0 pretvore u 1, onda bi slika mogla biti svjetlija kod slabije izoliranog kabela. Al fakat to su samo nagadjanja. Takav nekakav princip bi vrijedio kod analognog prijenosa signala, kod digitalnog se ocekuju 'iskrice', al da i kod digitalnog dolazi do "analognih" promjena... Ne znam.

[dmr]

Mislim da se ipak se misli na iskrice, nesto slicno kao kod satelitskih antena
"Sparklies are black or white 'hard' interference dots (as opposed to the 'soft' interference patterns of terrestrial television), caused either by too weak or too strong a signal."
Nego jesi li probao drugi kabel?