Understanding HDMI

I have been around this HDMI- High Definition Multimedia Interface. Now since it first converted from DVI- Digital Visual Interface. I was thinking I had it figured out a couple years ago… Now it seems as the equipment gets fancier and the applications get more advanced and the numbers of different wires and their design states change, it continues to cause me more issues. There is one thing you can count on and that is: “you cannot count on anything.” HDMI, as I stated in a earlier news letter, is great when the system is simple, add to the equation HDMI distribution a variety of devices including switches and multiple generations of wires and soon you have a very complicated mixed bag of results. Here is an example:
I have been working on a Church video system which has 4 HDMI fed monitors a 1×4 HDMI active splitter with a consumer grade camcorder and 2 other pro PTZ (pan, tilt, zoom) cameras, computer and Blu-ray switched by a Kramer 9 input scaling switch which has both HDMI and VGA outputs. I had the HDMI output of the consumer camera running through an HDMI cable which I had coupled to a longer cable for movement of the camera. When I plugged the camera in without the extension wire, the camera developed a noise in the picture which looked almost like tape dropout from the days of video tape. Also I notice that the active 1×2 splitter which is set up to allow monitoring of the camera prior to switching developed a power green LED without having its power port plugged in, and when power port was plugged in, the noise level from that camera was roughly 10 times worse. The long and short of it was that a specific HDMI wire was passing or cutting off the power leg (within the HDMI cable) and letting the system work fine when it was in series with the installation. When this wire was removed, the problem occurred. It took me over an hour to figure this out. It did not occur to me that a good HDMI wire was actually bad for the installation.
Not sure whether or not we will see more issues like this on a consumer type system but I can tell you that the interplay of HDMI wires, equipment splitters, settings, and play and receive signals act in ways which are almost impossible to predict. If having trouble with control and or logic operation of your system it is important to both turn on and or off HDMI related switches within all pieces of gear associated with the system, including ones hooked up to inputs which are not being used.
Let me give you an example:
Customer calls and says that the auto speaker switch on his Sony TV no longer works when the Sony surround receiver is turned on/off, as it did when I installed it. This was not the first time I had heard of this problem as my own system had quit working in the same way… (Insert plumber with leaky faucet). Customer had hooked up his PC via HDMI to a separate input on the TV. You would not think that this would cause a problem, however apparently HDMI signals are constantly looked at or listened to for control- command related items at all times on all inputs. I looked for the switch (in menu) of the pc monitor output on the computer too allow for the HDMI control portion to be shut off and could find no such switch. I also hooked the computer output to a open HDMI input on the Sony surround only to find the same problem reoccurring (auto speaker select) TV/Amp not working.
Lastly, here is a problem I discovered in Sony surround receivers not receiving Dolby Digital, no blue light on the front. I turns out that when you select in the HDMI control section TV+Amp as the configuration that it blocks the amp from working in Dolby Digital apparently because it figures the TV cannot work in Dolby Digital so neither can the amp?? I can only guess that because the play or source device cannot distinguish which piece is being used it can only export a non Dolby Digital signal.
If you have ever heard a Dolby Surround or especially a Dolby Digital surround playing without a center channel speaker the spoken word becomes almost impossible to hear and one complaint I often hear from people is the sound goes up and down, loud to quiet and the volume is never correct. This is caused by the same problem, a surround amp processing out the center channel out of the stereo signal or digital signal and then not routing that sound to a center channel speaker (often times because there is not one) or it has become disconnected, shorted or the amp has lost its center channel amp.
I am thinking that running HDMI adaptor to a DVI back to HDMI might help some of these problems.. this would work only in cases where you did not need the audio supplied by HDMI and the control was causing you problems.
I will get back to you on this!