Film-Tech Forum ARCHIVE: DVI cable lengths

This is topic DVI cable lengths in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Frank Angel (Member # 248) on 06-19-2009, 04:56 AM:

What is the lenght limit for DVI cable? I know it's not particularly long but someone thought it was only 6 to 10ft. We are going from a Barco scaler to the projector. Can we get away with a cable, say, 15ft? The other alternative would be going to one of those transmitter DVI to CAT5e and then to the receiver CAT5e to DVI boxes. We have found those to be fairly ify, as in sometimes they work, sometimes they don't.

It would certainly be easier if we just could deal with a longer DVI cable.

Posted by Chris Slycord (Member # 4239) on 06-19-2009, 11:35 AM:

Officially, the specs of DVI mandate that it to maintain a signal at 5 meters (16 feet), so it should work (and in many cases you can go longer than that too).

Posted by Ronnie Lai (Member # 5253) on 06-19-2009, 12:17 PM:

There should be some longer length cables for DVI made by Extron, do take a look in their catalogue.

Posted by Brad Miller (Member # 2) on 06-19-2009, 12:37 PM:

At 35 feet it gets questionable. I have used 35 footers with success, but at 50 feet the signal is definitely degraded beyond use.

Posted by Tristan Lane (Member # 1169) on 06-19-2009, 02:29 PM:

I've successfully used a 50 foot DVI cable with the use of a distribution amplifier. Content was 1280x720, with no sign of signal loss. I think higher resolutions would be more affected.

Posted by Robert Minichino (Member # 3495) on 06-19-2009, 02:37 PM:

The biggest factors in the maximum length of a DVI cable run are the resolution and frame rate transmitted (determines the frequency), the cable's capacitance per foot, and the ability of the transmitter to adequately drive the load presented by the cable.

DVI cable capacitance doesn't seem to vary too much, but the drive ability of various DVI devices seems to vary greatly. A distribution amplifier should have a stout output and would generally do better than connecting your long cable directly to the device's output.

Posted by Mike Babb (Member # 1379) on 06-19-2009, 03:02 PM:

I've had problems with 35 footers, relocated the scaler and used 6 footers, no problem at all. I should note that I tried a booster first and it worked intermittently, mostly well but occasionally not for whatever reason.

Posted by Steve Guttag (Member # 268) on 06-20-2009, 11:57 AM:

Okay....here is the scoop...again.

DVI and HDMI rules of thumb... 15' on straight cables with no other electronic means...anything longer and you are gambling, unless you know your cable manufacturer as well as the source and the display since they ALL must be working within their spec.

If your cable manufacturer does not have their prices go up geometrically after 15-feet...be very suspicious. I highly recommend Extron cables as one goes longer as they really do perform as claimed...they are not merely longer cables. Under 15-feet...most cables should work, by design.

So how to break the 15-foot barrier?

There are cable equalizers that will let one use a DVI cable up to about 200-feet! Mind you, that 200' cable is going to set you back many hundreds (if it is worth using) and then you are going to add another $250 or so for the equalizer to make it actually work.

There are the Cat 5 solutions. I can certainly testify that Extron's definitely work though you should/must use SHIELDED Cat 5 cable as well as shielded ends. I've successfully gone nearly 200-feet with them (720p) without problems. It is nice to be able to move both picture and sound (via HDMI) over just two Cat 5e cables. 1080p/60 signals would be limited to just 100-feet though.

If you really want to work long distance...there is but one sure-fire solution...fiber optics. There are solutions from Extron, Gefen and others that will let you go over 1,500 feet. The tooling is still a bit pricey to make one's own fiber ends but there are sources for pre-terminated fiber optic cables. Then again, with bandwidths going up...having the ability to make fiber cables is going to be essential.

Depending on the source...one could convert DVI to HDSDI and run just a single RG-6 cable too. I like HDSDI...great images, easy to work with cable, not too costly, can have video and audio over the same cable.

Steve

Posted by Jarret Chessell (Member # 5077) on 06-20-2009, 07:29 PM:

If you're only looking to get 720p you might be better of using coax. You can easily go under 100ft with RG6 or RG59 coax cables, this is also a lot cheaper than buying a high quality DVI or HDMI cable.

Posted by Steve Guttag (Member # 268) on 06-21-2009, 06:15 AM:

Providing you have an analog version of the signal...sometimes there is only the DVI version. There is nothing wrong with using analog and the cabling is, at present, easier to work with and can certainly go a decent length.

Steve

Posted by Jarret Chessell (Member # 5077) on 06-27-2009, 07:23 PM:

I just wanted to put up a link to an article about HDMI cables.

Long HDMI Cable Bench Tests

It's an interesting read, however, when you're finished reading it you'll probably find that you have more questions than answers...

If you look through the collection of articles they have, they do have some very interesting reading on other topics that would be related to other aspects of cinema equipment.

Posted by Julio Roberto (Member # 4976) on 06-28-2009, 05:01 AM:

Well, a lot of these "audiophiles" sites/magazines/tests want to insist on the notion that a $10 cable is "worse" than a $1000 cable and that they can hear/see the difference.

And sometimes they'll even argue POWER cables, that hook say an amplifier to the plug in your house, make a huge difference.

But after all the hoola, and considering how they "spent months" readying their "experiment", the conclusions are pretty much what everybody should know by now.

In my own words: "for short lenghts, say under 12 feet, any non defective cable, manufactured to meet the intended specs, will produce 100% perfect indistinguishable results". Over that, you need to start worrying about specs A BIT. Over around +35 feet and you REALLY need to worry about specs. Specs DOES NOT equal price and there is no need for any cable, no matter how long, to be too expensive, although they often are, but only because of mark up, not because of true cost, but you can find cheap ones that do just the same job.

And in their words in this article:

quote:
Your take-away from all this should be the following:

At lengths less than 4 meters you can just about use silly string (OK, not really) and get HDMI to pass at any current resolution. At less than 3 meters you'll even extend that to 12-bit color and possibly the next crazy idea HDMI Licensing decides to throw at consumers. Don't spend a lot on these cables and if you want to save money you won't let anyone at a big box store talk you into buying from them.
At long lengths (over 10 meters) you really need to pay attention to the manufacturer if you don't want to risk running into potential problems with 1080p and future formats such as Deep Color. With that said, just about any cable at or under 10 meters will pass 720p/1080i and nearly everyone will pass 1080p at 8-bit color as well.
If you have an existing HDMI cable and are running into problems, we'd suggest at least attempting the insertion of an active component at the sink (display) side. This is going to be far cheaper than ripping out your walls and re-running new cables - and likely just as effective.
HDMI has proven to be a moving target and there is no telling what crazy (likely unnecessary) format they will try to push down the cable next. Due to this, it's always good to "overbuild" your cable install, especially if it's a longer distance and going to end up behind drywall.
If you're not prone to upgraditis and think 1080p will be your maximum resolution for the life of your install, don't sweat it...

Of course there are entire industries, magazines, and leagues of people that breathe on expensive cables, so they are gonna tell you otherwise. Oh well, only thing at stake is money if they are chosen to be believed.

Posted by Geena Phillips (Member # 3726) on 06-28-2009, 01:45 PM:

BTW, I recently found a website with REALLY good cable prices.

Posted by Bill Enos (Member # 440) on 06-28-2009, 03:23 PM:

Just keep in mind when reading the magazine "tests and experiments" that magazines are shills for their advertisers.

Posted by Jarret Chessell (Member # 5077) on 06-29-2009, 01:10 AM:

I think it's important to note that in the link I posted above, when they're spewing out the results they ended up showing that some of the uber high-end uber expensive cables were less reliable than some of the middle class cables. It seems they feel that noise reduction circuitry within the a/v gear has more of an impact than the cables in some cases... which would explain some of the quality differences i've seen doing residential installs. Maybe bargain priced TV's and dvd players are the real issue.

Posted by Scott Norwood (Member # 30) on 06-29-2009, 08:01 AM:

The "audiophile" cable marketing is pretty funny. From what I've seen, recording studios use regular bulk cable from Belden, Canare, etc. If the people who are making the recordings don't see the value in super-expensive cables, why would they make a difference at home when listening to the same recordings?