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100ft HDMI cables - WDTV Live yes, Mac Mini no?

post #1 of 18
1/7/11 at 3:06pm
Thread Starter 
Hi, my first post.

I've got a unique, confusing problem that I hope someone can help lead me to solve, and I hope this is the right forum. I haven't found anything anywhere else.

We have created a 3-wall projection theater in an art museum, driven by 4 Mac Minis, using Renewed Vision's ProVideoPlayer to sync all 4 computers and their projectors (4 Epson 8350 models).

The high-speed HDMI cables we built into the walls are 75 ft long (2 of them) and the other two are ~100ft long.
The left & right walls have one projector each, and the longer front/center wall (25ft) has two 8350's projecting on it for an extra wide (poorly edge blended :]) HD image.

It was risky to have such long cables I realize, but they worked with our first projection solution: 4 Western Digital WDTV Live Plus media boxes, and they pushed the 1080p quicktime (7.5 MBit) videos with no problem. No flicker, no sparkle, nothing. Beautiful picture, but the open source software and synching was an impossible nightmare, and we ended up going with Mac Minis and ProVideoPlayer.

It appears as if the Mac Minis' graphics cards or HDMI signal are not as good as the WDTV Live boxes'. Two of the Minis do play perfectly (the front right projector and the right wall) but the center/front left and left wall images are randomly flickering and sparkling, and cutting out completely at times. I can't believe that the little $89 dollar WD boxes have a stronger HDMI signal, but that is the only conclusion I can see, since they are both pushing through the same cables. And the two working Minis are both on different lengths of cable.)

We bought an extender for one of the projectors to test if that would help, but we get a blue screen and a "Not supported" error from the projector. It says "Not supported. H: 67.50 kHz V: 49.82 Hz"

The extender we bought is "HDMI Extender - HDMI v1.3a Compliant w/Active Equalizing" (can't post the URL yet, but it's from HDTV Supply.com)

It's HDMI 1.3, and the projector is HDMI 1.3 capable, and I thought I read the Minis would output anything from HDMI 1.2 to 1.4.

The Minis obviously output different frequencies, and we have tried 50, 60 kHz, (these work best) and several others.
Can anyone enlighten me as to what might be wrong here? This is brand new territory for me and my colleagues.

I noticed a lot of people on the "Home Theater Computer > Mac" forum recommend the Gefen HDMI Detective; do you think this would be applicable?

Thanks!
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post #2 of 18
1/7/11 at 4:19pm
Quote:
Originally Posted by CarlBlochHD View Post
Hi, my first post.

I've got a unique, confusing problem that I hope someone can help lead me to solve, and I hope this is the right forum. I haven't found anything anywhere else.

We have created a 3-wall projection theater in an art museum, driven by 4 Mac Minis, using Renewed Vision's ProVideoPlayer to sync all 4 computers and their projectors (4 Epson 8350 models).

The high-speed HDMI cables we built into the walls are 75 ft long (2 of them) and the other two are ~100ft long.
The left & right walls have one projector each, and the longer front/center wall (25ft) has two 8350's projecting on it for an extra wide (poorly edge blended :]) HD image.

...
Removed by author
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post #3 of 18
1/7/11 at 5:04pm
Quote:
Originally Posted by CarlBlochHD View Post
The high-speed HDMI cables we built into the walls are 75 ft long (2 of them) and the other two are ~100ft long.
There are no 75' or 100' high speed HDMI cables. Longest certified high-speed HDMI cable I have seen is 25'. Doesn't mean you cannot run longer distances, just there are no guarantees.
Quote:
I can't believe that the little $89 dollar WD boxes have a stronger HDMI signal...
Why? WD has been in business longer than Apple and has supplied a lot of product to Apple over the years.
Quote:
The extender we bought is "HDMI Extender - HDMI v1.3a Compliant w/Active Equalizing"
After market HDMI cable powered devices have a poor track record. Even the ones with a wall wart aren't too good. They attempt to address one of the issues of using long cable, the attenuation of high frequency components of the square wave. They do nothing for the more serious issues of intra-pair and inter-pair skew.
Quote:
It's HDMI 1.3, and the projector is HDMI 1.3 capable, and I thought I read the Minis would output anything from HDMI 1.2 to 1.4.
Sources don't put out HDMI 1.2, HDMI 1.3, or HDMI 1.4. They put out data at some bit rate. The bit rate is one of your potential problems.
Quote:
Can anyone enlighten me as to what might be wrong here?
What you did wrong was jump into something without doing the requisite research. Making HDMI work at long distances is something of an art. The good thing is that at resolutions up to 1080i/30 or 720p/60 and 8 bit color, it is quite doable. Increase the resolution, frame rate, or color depth and it becomes problematic.

HDMI performance depends on the cable, all the electronics, the bit rate and the environment. You changed the electronics. That could be the problem. You may also have changed the bit rate. What resolution, frame rate, and color depth were you using with the WD devices? And with the Mac devices?
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post #4 of 18
1/11/11 at 9:57am
Thread Starter 
Thanks for the help gentlemen. Sorry about the delay in responding; I got the stomach flu and am just now getting back to life.

Quote:
Originally Posted by Colm View Post

HDMI performance depends on the cable, all the electronics, the bit rate and the environment. You changed the electronics. That could be the problem. You may also have changed the bit rate. What resolution, frame rate, and color depth were you using with the WD devices? And with the Mac devices?

We actually were using the same Quicktime movie files on the WDTV Live boxes as we were on the Mac Minis. 1920 x 1080p, H.264, 6.1 Mbit, 8 bit color depth.

Now, per the ProVideoPlayer recommendations for non-jittery playback, we are running 22 MBit PhotoJPEG codec videos, and 3 of the 4 screens are running smoothly and without flicker & sparkle.

We actually got the HDMI booster/extender to work on the front wall left channel, but it won't work on the left wall with the same configuration. I suspect cable damage... I am going to try temporarily replacing the Mac Mini with another Mac to see how much of the problem is the graphics capabilities of the Mini.

Thx...
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post #5 of 18
1/11/11 at 11:13am
Belden & Blue Jeans Cable Shatter HDMI Record:

Quote:


OK, well it's not exactly something Guinness was excited about, but Belden did manage to run 1080p/60 signal through an unamplified 100-foot run of HDMI cable. That's about 30 meters for anyone majoring in metric-to-SEA conversion ratios - and far beyond what is considered possible in terms of unamplified HDMI capabilities.

http://www.audioholics.com/news/indu...er-hdmi-record

Belden/Bluejeans Runs An Unamplified 1080p/60 Digital Video Signal Over 100ft of Connectorized HDMI Cable:

http://www.hdtvmagazine.com/news/200...hdmi_cable.php
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post #6 of 18
1/11/11 at 2:41pm
Quote:
Originally Posted by CarlBlochHD View Post

I am going to try temporarily replacing the Mac Mini with another Mac to see how much of the problem is the graphics capabilities of the Mini.

Good idea. I thought of one other thing. Do the Mac Minis you are using have a HDMI port, or display port. Converting display port to HDMI seems to be problematic at times from what I have seen in other threads.
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post #7 of 18
1/11/11 at 3:11pm
Thread Starter 
Quote:
Originally Posted by Colm View Post

Good idea. I thought of one other thing. Do the Mac Minis you are using have a HDMI port, or display port. Converting display port to HDMI seems to be problematic at times from what I have seen in other threads.

The minis are brand new with HDMI ports (and a MDP, but we're not using it).

Yeah, I wondered myself if doing tests with a laptop going from MDP to an HDMI adapter would give us accurate results.
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post #8 of 18
1/11/11 at 4:25pm
Quote:
Originally Posted by CarlBlochHD View Post

I suspect cable damage...

Could be something as simple as someone pulled too hard on the cable. The geometry is important for a number of the parameters that affect cable performance. Pull too hard and the geometry changes. Could also be the cable is running through a slightly less hospitable electrical environment than the others.

You didn't say what make and model of HDMI cables you are using. I assume they are 22 AWG or 24 AWG. If you have to swap one out, Blue Jeans Cable Series 1 is about as good as it gets. It is constructed with Belden bonded-pair cable stock which minimizes intra-pair skew, one of the parameters that causes issues with long runs.
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post #9 of 18
1/11/11 at 7:58pm
Quote:
Originally Posted by CarlBlochHD View Post
The minis are brand new with HDMI ports (and a MDP, but we're not using it).

Yeah, I wondered myself if doing tests with a laptop going from MDP to an HDMI adapter would give us accurate results.
Try 1080i/720p resolutions and see if that helps. If those resolutions work, then you can run at standard speed but not high speed (1080p/60 or 1080p/24 3D).
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post #10 of 18
1/11/11 at 10:25pm
Quote:
Originally Posted by alk3997 View Post

Also watch out for crimping...

Also the radius of the bends in the cable... Do not bend tighter than the minimum bend radius specified by the manufacturer of the cable. If you don't have that figure, 10 times the diameter of the cable is a good rule of thumb for the minimum bend radius.
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post #11 of 18
1/12/11 at 8:49am
Thread Starter 
OK, it turns out that when we set the projector's resolution to 1080i, no more flicker. I can't tell any difference in the quality of picture & graphics either; it looks like the other screens. The movies are progressive, so I'm not sure what it's doing, other than sending a less bandwidth-heavy signal.

Whateverit's awesome!

Thanks for all your ideas.
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post #12 of 18
1/12/11 at 9:53am
Quote:
Originally Posted by CarlBlochHD View Post

OK, it turns out that when we set the projector's resolution to 1080i, no more flicker. I can't tell any difference in the quality of picture & graphics either; it looks like the other screens. The movies are progressive, so I'm not sure what it's doing, other than sending a less bandwidth-heavy signal.

Whatever—it's awesome!

Thanks for all your ideas.

Deleted
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post #13 of 18
1/13/11 at 11:52am
Thread Starter 
So, it looks like the no-flicker honeymoon is over.

The 1080i solution on the left wall worked for about 8 hours yesterday, and then the flicker began again. Today, it was flickering on startup. I wish this revealed something to me.

Any ideas, based on this latest development?

Thx!
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post #14 of 18
1/13/11 at 1:14pm
Quote:
Originally Posted by CarlBlochHD View Post

So, it looks like the no-flicker honeymoon is over.

The 1080i solution on the left wall worked for about 8 hours yesterday, and then the flicker began again. Today, it was flickering on startup. I wish this revealed something to me.

Any ideas, based on this latest development?

Thx!

Check to see if the player didn't restore the resolution to 1080p. What would explain why the flicker was fixed and then returned.

(Restored append)
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post #15 of 18
3/1/11 at 9:28am
Quote:
Originally Posted by Featuredtech1 View Post

You are getting drop offs and flicker because it is HDMI. It is by far the most unpredictable signal type. Over cat5 extenders are what you are going to want to use at that length. 65ft (20m) is as far as you want to go with an HDMI cable. There are a few cat5 extenders out there that get you far distances. I.E. Gefen, Atlona, Cables to go, etc. go here:

featuredtechnologies.com

Featuredtechnologies, this problem was solved over a month ago. Might want to check the dates before posting.

If you look back you'll see that the Cat 5 (or 6) soluation wasn't a possibility for them.

I will attempt to restore the posts I deleted (during a dispute with the board's owners that has since been resolved).

Bottom line in this case was that the could run at standard speed but couldn't at high speed. The player apparently went back to 1080p which restored "flickering".
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post #16 of 18
3/2/11 at 9:35am
Quote:
Originally Posted by Featuredtech1 View Post

You are getting drop offs and flicker because it is HDMI. It is by far the most unpredictable signal type. Over cat5 extenders are what you are going to want to use at that length. 65ft (20m) is as far as you want to go with an HDMI cable. There are a few cat5 extenders out there that get you far distances. I.E. Gefen, Atlona, Cables to go, etc. go here:

featuredtechnologies.com

It is a fallacy that you can go further with CAT5 extenders. With a good quality HDMI cable (Belden) I have done 220ft (67m) with an EQ at the end operating at 1080p 60Hz 24bit color - with perfect reproduction, no sparlies, or flickering. I also did eye diagram tests to verify the link had adequate margin to meet the HDMI mask test - which it did.

The HDMI connector creates less of a discontinuity to the transmission line. The 8P8C (most call it RJ45) connector is HORRIBLE at high frequencies and creates big signal reflections. I have tested many, many CAT5 HDMI extenders and CAT5, CAT6, and a CAT7 cable. The CAT7 solution may be able to achieve what a good quality HDMI cable and a good EQ can do. Note that CAT5 solutions require receive-side equalization as well.

The reason many HDMI cables fail at long lengths, even with an EQ, is the intra-pair skew that develops along the cable. The individual shielding on each TMDS pair allows a common-mode signal to develop if the pair twist isn't perfectly symmetric. This common-mode signal travels at a different velocity down the cable then a differential-mode signal and you end up with a very distorted waveform at the end. An EQ can not fix this.

A standard CAT5 cable leaves each pair unshielded (Unshielded Twisted Pair, UTP). This inhibits the development of a common-mode signal down the cable and therefore helps to keep the signal on the pair in-phase with each other (low intra-pair skew).

So for medium length runs (30ft to 100ft) a cheap CAT5 will usually work better than a cheap HDMI cable due to the bad intra-pair skew that can develop in a poor quality STP cable. But a high quality HDMI cable will work to a longer distance than any CAT5 cable. I am talking only about active (equalized) links.
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post #17 of 18
3/8/11 at 5:22pm
Quote:
Originally Posted by FiberOpticDude View Post

a high quality HDMI cable will work to a longer distance than any CAT5 cable. I am talking only about active (equalized) links.

Many HDMI receiver IC's have equalization built-in, so wouldn't the equalizers in the cables be a waste if the receiver already has good EQ?
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post #18 of 18
3/10/11 at 9:37pm
Yes, many HDMI receivers have built in equalization but it is a modest amount. It might be 16dB at 825MHz and built into the actual CMOS HDMI receiver chip. Very few televisions (actually none that I know of) use the high-end equalization that a separate, stand-alone equalization chip can provide: 40dB at 825MHz.

I have seen an HDTV (with the modest built-in equalization) work perfectly with up to a maximum of 50ft, 26AWG HDMI cable at 1080p 60Hz. That same system worked perfectly up to a maximum of 150ft (three series 50ft HDMI cables) with a stand-alone equalizer at the end of the cables, also at 1080p 60Hz.

Television manufacturers don't put that chip in their TV's because they are too cost sensitive. But it might be possible that a high-end EQ could be in high-end projectors where they aren't as cost sensitive.
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