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Discussion Starter · #1 ·
Up to the very last time this question "why" didn't exist for me. The situation looked absolutely clear: the source (say, DVD) is digital, the viewing device (projector) is also digital so the best way to transfer data between them is without any digital-analog transformations, i.e. via DVI.

I was also very concerned with the question why JVC SX21 (= Maxx 1400) doesn't support the native resolution 1400x1050 via DVI input and I even talked with a JVC product manager about it (see this thread ).

It looked important because I have a notebook (Compaq Evo N600c) with 1400x1050 native resolution. I know that video data are digitally transferred between video card and LCD panel and I thought it is exactly DVI. So some extension to the notebook (like docking station) should exist which would add the DVI output to it.


But yesterday I finally decided to check what exactly can be implemented if I have, say SX21 and if 1400x1050 is now supported via its DVI input (via software upgrade).

And I haven't found any reasonable way how to do it!


1. I haven't found any way how to add DVI port to my notebook and I've even found out that internal video interface in notebooks is not DVI at all (so adding DVI port is not that simple task)!!

As I can see now there are almost (or at all?) no notebooks with DVI output and only very very few with the docking stations with DVI are available (and N600c is not between them :( ).


2. OK, my notebook was a wrong choice this way (and I'm pretty sure the most of you would say the same about your equipment, of course, if you are not going to use the desktop computer making twice more noise than any projector, not talking about notebooks).

So maybe there is some DVD player (for any money) with DVI output supporting 1400x1050?

And again: NO!!! I haven't found ANY such a player: indeed, I found only one [hacked one - with a 'special' board, not from the player's manufacturer] with DVI output but(!) even this one definitely doesn't support 1400x1050!


3. Hmmm... OK. Maybe something more difficult, like DVD-> video processor ->projector?

Between all the processors I've found only one(!) (CS-1) which has 1400x1050 support and even in this case this resolution is not initially supported but it's added via software upgrade...

In such a situation I immediately think about the following:

they support so many resolutions and have so many software upgrades that it's hard to believe that it's not buggy and also in such a generic approach it's hard to believe that it can be as efficient as other devices with 'more standard' resolutions supported by hardware.

And I see also another problem in this chain (with DVD player and processor):

this variant means that DVD player makes some digital->analog transformation applying its own algorithms for better output quality (player and processor are connected via component cables in the best case). After that processor first makes analog->digital transformation and also applies its own algorithms also for having better result's quality. But(!) as I've heard from specialists the result of such subsequent transformations and different algorithms applications can be rather bad...


And I've found also another very 'interesting' problem for any of these variants:

it's a DVI cable length. It seems that DVI cables are usually rather short. And when they are longer the video quality is degrading so significantly that 'simple' monitor (VGA) cable would be even better.

The usual place for projector is on the ceiling. So if you want to use DVI you should mount the DVI source device also to your ceiling near the projector: for DVD player it's impossible (you need to put disks into it) and even for processor (which is not very tiny device) it would look strange on the ceiling, I think :)


So I have a question for all those who are very interested in DVI inputs for projectors here:

please say how exactly are you going to organize the chain from the DVD disk to the DVI input of your [future or already existing] projector?


And also other questions:

Have anybody already implemented such a chain: 'DVD->??->via DVI->projector' and what is the result comparing with the analog input?


Maybe somebody also has some experience (or information) on video quality when using all these transformations and recalculations in the DVD->processor->projector chain. How is that?

Do you think it's really better to use DVI between processor and projector instead of analog cable (say, component or VGA) if you anyway need to use analog one between DVD player and processor?
 

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Right on all counts.


DVI was one of those 'committee decisions', where designing a horse resulted in a hippopotamus. There are about 8 different versions of DVI, and yes, the cable length is completely inappropriate. But remember, their most important consideration was copy-protection.


It doesnt matter a whole lot though, as most current projectors can only do a max rez of ~800x640 via DVI. Plus, the general consensus here is VGA can give as good, or maybe a better image than with DVI, and with HD rez. Futureproof and stabilized. This is what I am/will be using.


A better technical solution for digital link would be some sort of LVDS (serial low-voltage differential signalling), like firewire. I think Mits has gone this route. But the Powers That Be are deciding our future right now. Vote with your wallet.


If you have no choice except DVI for some reason, just set up an HTPC. It'll be a standard PeeCee with DVD+R, Powerstrip, and an ATI Radeon video card.
 

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Hi Burnt,


I'm a newbie, and this thread is very informative. I'm building a HTPC with ATI Radeon 9700 to output DVI to a NEC HT1000 projector. Is the resolution restricted with this arrangement? I am hoping that I'll get at least the 1024 x 728 (XGA) via this setup. Also, what is the cable-length restriction for DVI?


Thanks
 

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Brian, you're going to have a kick-butt setup. You will be able to supply the HT1000 with it's native resolution via DVI, and that is exactly what you want.


I have no idea where you got 800x640 from, Burnt, and you're simply wrong about what the "general consensus" is about DVI vs. VGA quality. I am running 1280x1024 over DVI on my projector (*** Evolution), as are others with JVC G150s or Hitachi 5500s. Of course, none of us can run at the native panel resolution (1365x1024), which is kind of silly, but that's still a lot more than 800x640. And more importantly, it looks measurably better than the VGA connection. Do a search on this forum about DVI and you'll see that the consensus is exactly the opposite of what Burnt is claiming: DVI almost always looks better than VGA for an otherwise equivalent setup. (I did say "almost".)


I personally think DVI is unfairly judged, in part because people underestimate the job that it has to do. Let's not forget that DVI provides an uncompressed digital video connection---after the source material has been decompressed, deinterlaced, and scaled. As a result, it needs a lot of bandwidth. DVI's maximum single-link data rate peaks at 4Gbps for a single-link connection---more than enough for [email protected] with 24 bits per pixel. If you need more resolution or color depth, dual-link connections are possible (but probably not available, due to lack of market demand).


By comparison, Firewire can't even come close. The current version tops out at 400Mbps---not even enough for [email protected] (but enough for interlaced DVD). Faster Firewire connections are on the horizon, but the 3200Gbps version is going to require fiber optic connections, at least at first. The Firewire ports that you see arriving on video equipment are very likely for compressed video. That's fine, I'm glad we're getting that, but at some point you're going to want to decompress, deinterlace, and scale the signal, and then you won't have the bandwidth on Firewire to cover it. So Firewire is not a substitute for DVI's ability to transmit uncompressed video.


There simply is no commonly available digital cable connection out there, besides DVI, with a 4Gbps data rate. Not USB, not Firewire, not Ethernet. When you're pushing 4Gbps (or 2Gbps, as I regularly achieve with [email protected]), it shouldn't be a surprise that cable length and cable quality are an issue.


Speaking of fiber optic, though, if you really want a long DVI cable, you can get one for about $650 that uses fiber optic transmission and can go 20 meters easy. Depending on the cost of the rest of your system, that may be worth it.
 

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Michael, very informative post.
Quote:
By comparison, Firewire can't even come close. The current version tops out at 400Mbps---not even enough for [email protected] (but enough for interlaced DVD).
This statement made me very curious.

I have a external IEEE1394 (aka Firewire) DVD-ROM drive on my PC. I sometimes use this to watch dvds via PowerDVD XP.

How is this possible when Firewire's bandwidth is lower than that of current dvd ??


Also... I'm trying to calculate the bandwidth required for 480p dvd.

720x480x60 = 20736000 bps = 20.736 Mbps

And I'm having trouble. :( I know this is wrong. Can you any one shed a light for me ? :D
 

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Cuz the firewire is carrying the compressed data right off the DVD. It is being decompressed in the PC and then sent to your monitor as RGB or DVI.


BB
 

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Brandon B is correct, the DVD actually contains compressed DVD information. The bit rate of compressed DVD tops out at 9.8Mbps, if I remember correctly, although the average DVD comes in much lower than that.


Tango, the reason that your math is wrong is because you forgot the 24 bits per pixel. So the bit rate for 480p is 720 x 480 x 60 x 24 = 498Mbps. But in fact, DVD video is interlaced (480i), not progressive (480p), so its bit rate is half that, or 249Mbps. As I stated above, 480i can fit through a 400Mbps Firewire connection, but as soon as you do any deinterlacing or scaling you'll exceed Firewire's capacity.
 

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Quote:
Tango, the reason that your math is wrong is because you forgot the 24 bits per pixel. So the bit rate for 480p is 720 x 480 x 60 x 24 = 498Mbps.
Michael, thanks for the reply. :)

one last question! :D Inquiring mind want to know.

"24 bits per pixel" is this because dvd is in 24 bit color system ??
 

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prog·nos·ti·cate tr.v.

prog·nos·ti·cat·ed, prog·nos·ti·cat·ing, prog·nos·ti·cates

To predict according to present indications or signs; foretell. See Synonyms at predict. To foreshadow; portend: urban renewal that prognosticates a social and cultural renaissance.

--------------------------------------------------------------------------------

[Middle English pronosticaten, from Medieval Latin prognsticre, prognstict-, from Latin prognsticum, sign of the future, from Greek prognstikon, from neuter of prognstikos, foreknowing ; see prognostic.]

--------------------------------------------------------------------------------

prog·nosti·cation n.

prog·nosti·cative adj.

prog·nosti·cator n.


Perhaps a quick perusal of a dictionary would be a prudent move prior to your next reply.

pronunciation
 

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Alan, if you don't do something about this, I will.
 

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OK, back to the topic at hand, shall we?
Quote:
one last question! Inquiring mind want to know. "24 bits per pixel" is this because dvd is in 24 bit color system ??
Well I was asuming a 24-bit RGB color system because that's what DVI uses.


However, I don't think DVD's store color that way. Instead, I think they represent colors in the YUV component space. Furthermore, I believe that the color information (U,V) is sampled less frequently than the brightness (Y) information, because our eyes are less sensitive to color changes than they are to brigthness changes.


It is probably possible to save some bandwidth when transmitting uncompressed DVD video by using this original color format. But if you're going to do any deinterlacing and scaling, you'll have to convert to a RGB anyway, or at least to fully-sampled YUV, so you're back to your full bandwidth requirements.
 

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Since Burnt for some reason has seen fit to delete all of his posts surrounding our debate, I thought it fair to remove all mine too, since they look rather irrelevant without his.
 

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Discussion Starter · #14 ·
Quote:
Originally posted by Michael Grant



Speaking of fiber optic, though, if you really want a long DVI cable, you can get one for about $650 that uses fiber optic transmission and can go 20 meters easy. Depending on the cost of the rest of your system, that may be worth it.
Michael,


I'm glad that there is a solution for the DVI cable length problem, even rather expensive one. Thanks for the info.


But I still have a question about the reasonable way of connecting the devices 'before' the projector if you are going to use its DVI input.

If I notices correctly, in one of your [deleted now] messages you've mentioned that you're using (or you're going to use) the DVI output of some video processor right 'before' your projector.


Please say how DVD player and video processor are connected in your [maybe, potential] system?


And what do you think is the most reasonable way to connect such devices in the situation when it's possible to choose any DVD player and any processor (of course, for having the best possible results on projector)?
 

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Here's what I have now:


DVD component output ---> scaler component input ---> scaler DVI output ---> projector DVI input


I'm pleased with the results, but if I had my way this is what I would have instead, a fully digital solution:


DVD SDI output ---> scaler SDI input ---> scaler DVI output ---> projector DVI input


This will provide the highest possible quality (in my opinion).


If money is tight, I would consider eliminating the scaler altogether and consider connecting the DVD player directly to the projector via the component inputs. This will still look very good if the projector's analog circuitry is good, particularly if it has a good deinterlacer/scaler chip inside. For example, the Infocus 7200 has the Faroudja chip, and it's hard to beat that even with an external scaler. So don't automatically assume you'll need an external scaler. The only problem with this approach, though, is now you'll need long component cables instead of a long DVI cable; that could reduce picture quality.


As for SDI: Do a search for SDI in this forum or the Video Processor forum to learn more about it. It's not available on DVD players that you buy at your average consumer electronics store. A couple of very high end DVD players have it, but a much cheaper route is to have a standard DVD player modified to add an SDI output. In contrast, several scalers (T-A-W Rock+, Key Digital Leeza/HD Leeza, Immersive aSimilator, Focus Enhancements Centerstage, Vigatec Dune) support SDI inputs.
 

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There's always the HTPC (Home Theater PC) route... although that's really a topic for another forum, that's how I'm going to be feeding my RPHDTV's DVI from all my sources... you may find it worth looking into.
 

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Duplicator, you're right, HTPC is a great option if you're up for it---and with the addition of a Holo3dGraph card you can get the best of both worlds.
 

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Quote:
Originally posted by Michael Grant
I would consider eliminating the scaler altogether and consider connecting the DVD player directly to the projector via the component inputs.
My old HT room was just upgraded with a component DVD player, and now a Projector with VGA inputs. I'm trying to find out what's the best way to connect them via component. I assume there are ready-made cables just for this purpose. I've got Y, Pr, Pb on one end and a D-sub on the other, and 15 feet in between.


Thanks!
 

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Quote:
Well I was asuming a 24-bit RGB color system because that's what DVI uses.


However, I don't think DVD's store color that way. Instead, I think they represent colors in the YUV component space. Furthermore, I believe that the color information (U,V) is sampled less frequently than the brightness (Y) information, because our eyes are less sensitive to color changes than they are to brigthness changes.


It is probably possible to save some bandwidth when transmitting uncompressed DVD video by using this original color format. But if you're going to do any deinterlacing and scaling, you'll have to convert to a RGB anyway, or at least to fully-sampled YUV, so you're back to your full bandwidth requirements.
Michael Grant,

Again, thank you for your informative/educational reply!


I'm afraid I have an another question. I know you're one of the best experts on these matters!! :D And your opinions are some of my most respected.

Quote:
Speaking of fiber optic, though, if you really want a long DVI cable, you can get one for about $650 that uses fiber optic transmission and can go 20 meters easy. Depending on the cost of the rest of your system, that may be worth it.
This optical DVI cable... doesn't this reduce quality ? Because the cable or converter in the cable has to convert electrical DVI signal into optical(pulses of light), and back into electrical in the end ?? I'm asking for your personal opinion/view on this. :)
 

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Quote:
Originally posted by Michael Grant
Since Burnt for some reason has seen fit to delete all of his posts surrounding our debate, I thought it fair to remove all mine too, since they look rather irrelevant without his.
That's probably best. I felt it was clear you are not open to the technical merits of any technology but DVI, and no one else seemed interested, so there's no sense in discussing it. No value was placed on the information I provided.



Aaand on that note, the time has come for me to sign off.


Some of you know that I used to own a Marantz VP12S1. When I sent it to Marantz Japan for warranty service, it was detained for more than 3 months. I was forced to file an international lawsuit, and Marantz and I have since reached amicable settlement. Yesterday that settlement was fully completed and I non-suited.


I should note that my warranty difficulties seem to have been a temporary glitch, and that others should not worry about sending your machine in for work, whether in Japan or the US. Marantz makes a very high-quality projector, evident if you've ever seen the inside of one, and normally service is good as well. I am not required to say these things, but I want to say them.


I have enjoyed the discussions I've had here with the intelligent readers. Although I have been constantly, viciously harassed by the 'less-educated' element, I've slapped back a few times too. Beyond me, why this is necessary, but it is.


I'd like to thank those brave souls who, not only dared to speak out for what is right, but also dared to give their email address to me. These few have gotten continuous updates (in backchannel) on my progress and all developements, from the beginning. Thanks for keeping my confidence.


And yes, I'd like to thank the Mods of the forum. Although they have not always necessarily been even-handed, they have been tolerant to a degree, of me and of others.


I'll hang around for a day or two, in case there's anything worth responding to, though as a rule I'll try not to respond.



One more thing. This is off-topic, but it's also my last post. Recently the Homeland Security Act was passed .

"The U.S. House of Representatives overwhelmingly passed legislation on Wednesday to create a Department of Homeland Security...."


This seems like another giant bureaucracy, only this one is doing the job the CIA and FBI were supposed to have been doing, but failed at. As a bonus, this new department's job is to surveil us, out of simple insecurity caused by these primitive terrorists, who got lucky once.


"...the measure would trigger the biggest U.S. government reorganization in a half century by rolling into the new department all or parts of 22 existing federal agencies, including the Coast Guard, Border Patrol and Secret Service. A chief aim is to avoid a repeat of the breakdowns in communication between the CIA and FBI exposed by the hijacked airliner attacks last year on the World Trade Center in New York and the Pentagon near Washington. While neither the FBI nor the CIA would be part of the new Cabinet-level department, the legislation seeks to bolster the analysis of their intelligence information."


But wait... this doesn't make sense. The two problem agencies are hardly involved! Ah, but they're too powerful, so let's subsume the FUNCTIONING agencies all into one gigantic, expensive one that doesn't actually function, yet is large enough to survive 'dans perpétuel', PLUS has the authority to hide information and mistakes under the cover of 'National Security'. (I wonder how much longer will I be able to make observations like this?)


I care about this, because I love this country.


"The revised measure dropped a bipartisan proposal contained in an earlier Senate version that would have created an independent commission to investigate the Sept. 11 attacks. Lawmakers vow to make a new push for such an inquiry when the new 108th Congress convenes in January, saying the nation

must find out what went wrong to permit the deadly attacks
."


What? OK, let's not look into what *actually* went wrong, before we make a major new move to fix it. Takes too much time... they have to (be seen as) doing something NOW.


Ugh.
 
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