HDMI, HDCP, and DVI questions - AVS Forum
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post #1 of 10 Old 07-25-2012, 11:43 AM - Thread Starter
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After much Googling, I've not found the answers to my questions. This post is probably going to go long, mainly because I'm wordy but also because this issue is a bit more involved than, "hey, it's not working!" Or mostly because I'm wordy. I realize this forum is more for home theater systems, but I've found AVS to be invaluable resource—plenty of knowledgable folks around here.

Ultimately what I'm trying to accomplish is to send 720p output from a new Mac Mini into a TriCaster and into our two XGA projectors. Like so:



If I use Thunderbolt to HDMI cable->Kramer VM-2Hxl HDMI 1:2 DA->HDMI to DVI Cable it works for a few minutes but goes black. I've also tried going from that Kramer unit to my Blackmagic HDMI to SDI converter and into our TriCaster but that goes black too after a while.

I've tried using HDMI->Kramer DA and then into the scaler and SDI converter but no luck there either. When we just used DVI out of our old PC this was not a problem and all the other hardware worked perfectly.

So here's my thought process, and where I have questions:
  1. Why is the screen blanking? I'm guessing HDMI/HDCP handshake issues, considering the signal path is running through multiple units, some of which do not support any kind of HDCP (the Extron scaler, for one). The Kramer HDMI DA has the same feature that the Gefen HDMI Detective has: it'll grab EDID info from the sink device, save it, and send this back to your source, regardless of the actual sink that's plugged into the output sides of your DA. In my case, I'm using the Blackmagic EDID info to get a bog standard 720p output from the Mac Mini; the scaler and the TriCaster handle this beautifully—when it works.
  2. My biggest unanswered question: I thought that HDMI was like DVI, that it didn't always require encryption. Am I mistaken? Is HDMI always encrypted, even when the content running over it needn't be? Do all HDMI equipped devices, including cameras, supply encrypted signals?
  3. If this is truly the case, what can I do to get my Mac Mini to work here? I still need to end up with a signal path that allows me to mix the output of the Mac on the TriCaster, as well as display the output from the Mac on the projectors without first going through the TriCaster. Hence the HDMI 1:2 DA. Our use of the TriCaster is to mix in signals from video cameras as well as the output from the Mac so that we can broadcast our service to other rooms on campus (via network and dedicated HD-SDI runs).

Any help on this topic, or other places to look for answers, would be tremendous.

Thanks!
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post #2 of 10 Old 07-25-2012, 12:21 PM
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AFAIK HDCP works the same way for DVI and HDMI.

Sounds like HDCP reauthentication is failing. Reauthentication occurs every 120 frames or 2 minutes, whichever comes first.
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post #3 of 10 Old 07-25-2012, 03:00 PM - Thread Starter
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So does that mean that HDMI is always trying to use HDCP encryption? This screen blanking occurs no matter what's happening, and as far as I know I'm not displaying any content that requires HDCP. This is just on the Mac desktop. So do Macs just run HDCP over HDMI all the time? Does HDMI do HDCP handshake/auth whether it's encrypting anything or not?
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post #4 of 10 Old 07-25-2012, 06:11 PM
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Don't know about Mac, but yes, some devices just encrypt all HD content instead of encrypting just the content that requires it.

The source is allowed to initiate authentication whenever it wants. It certainly has to do it before sending encrypted content. But It seems the exact timing is up to the designer.

Come to think of it, although HDCP essentially works the same with HDMI as with DVI, IIRC there are some minor differences which need to be taken into account when programming the transmitter. There are documents floating around the internet that speak to this. Don't remember the details, though, or the significance.
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post #5 of 10 Old 07-26-2012, 11:56 AM
 
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I can't talk Mac, but there are many PCs that generate HDCP encrypted output even when the source isn't. The reason is to have to keep from changing to encrypted output each time a Blu-Ray disc is played. Remember according to HDCP, every element that touches the video signal must be encrypted within the PC, if an encrypted source is played. It's why some people still couldn't play a Blu-Ray disc after upgrading their GPUs. The GPU was secure but the rest of the PC (such as the motherboard) was not. So, with that level of "security", it wouldn't surprise me if a PC output was encrypted even if the source was not an encrypted source.
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post #7 of 10 Old 07-10-2013, 09:40 AM
 
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Thanks for the back-up! Yes, even non-content protected material is HDCP encoded if the MacMini is connected to an HDCP-enabled display.
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post #8 of 10 Old 07-11-2013, 09:00 AM
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Hello Dittobox

Gefen HDMI Detective+ - are you sure about the feature set being matching by your DA! The key point with the HDMI Detective+ and the Dr HDMI (by HD Fury) being that they keep re-pinging the Source to mimic an active Display – that is not what I would expect with a DA with EDID management (those generally negotiate once at start up and that is it).

Mac Mini – we have run into problems in the past with Mac’s due to their power save settings when running in OSX, we have systems which run no problems when the Mac’s are in Win or other OS modes but fall over if you try and run them under OSX!!!

I’d try simplifying the system and see how that goes then add bits back in and see when the problems kick in.

Joe

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post #9 of 10 Old 07-11-2013, 09:17 AM
 
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Quote:
Originally Posted by Joe Fernand View Post

Hello Dittobox

Gefen HDMI Detective+ - are you sure about the feature set being matching by your DA! The key point with the HDMI Detective+ and the Dr HDMI (by HD Fury) being that they keep re-pinging the Source to mimic an active Display – that is not what I would expect with a DA with EDID management (those generally negotiate once at start up and that is it).

Mac Mini – we have run into problems in the past with Mac’s due to their power save settings when running in OSX, we have systems which run no problems when the Mac’s are in Win or other OS modes but fall over if you try and run them under OSX!!!

I’d try simplifying the system and see how that goes then add bits back in and see when the problems kick in.

Joe

Joe, check the dates. Dittobox hasn't been here in about a year. Argone01 was just supplying a white paper to backup last year's arguments. That's the only reason the thread came back up again.
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post #10 of 10 Old 07-11-2013, 09:20 AM
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Oops – I guess he got sorted then cool.gif

Joe

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