Diagnosing an HDMI system - Page 1
Forum section: electronics / general

author: Mike Warren
author_rank: Unknown
timestamp: August 14, 2013, 04:37:24 am
content: Not knowing much about HDMI, I'm hoping someone here can offer a suggestion to track down a problem.I have a Sony KDL-55EX720 55" LCD TV with a Panasonic DMR-PWT520 Bluray / HDD recorder and a computer connected. The HDD recorder is connected via an HDMI cable and the computer is connected via a DVI-HDMI adaptor and HDMI cable.My problem is that intermittently the TV mutes (video and audio) for about 3-5 seconds, but only when viewing the signal from the HDD recorder. It doesn't matter it the recorder is playing a file from it's hard drive, a DVD or bluray, an audio CD or live TV. It can sometimes go for as much as 3 or 4 days without failing, and sometimes might fail 5 times in an hour.I've tried a different HDMI cable and swapping the inputs on the TV.The HDD recorder is still under warranty and I think the TV might still just be in by about a month, but I know from past experience that each manufacturer will try to blame the other and say there is nothing wrong with their device. Which, I guess could be the case. Does HDMI suffer from incompatibility problems?Does anyone have any pointers for what I can test or try?

author: kizzap
author_rank: Unknown
timestamp: August 14, 2013, 04:49:48 am
content: try the HDD recorder on another TV, if it still causes issues, then it is obviously the issue.-kizzap

author: Mike Warren
author_rank: Unknown
timestamp: August 14, 2013, 05:20:16 am
content: Thanks for the reply. I don't have another HDMI TV. Even so, I'd need to watch it for days to have any idea.The reason for my post was mainly to find out if there was a way to determine if an HDMI signal is in spec. or perhaps a known problem with either of the devices.

author: Bored@Work
author_rank: Super Contributor
timestamp: August 14, 2013, 05:53:47 am
content: Determining if a HDMI signal is really in spec is a difficult issue, because HDMI is complex. The spec should be a thousand or more pages of documents. Agilent will happily take several 10 kEuro out of your hands for a real HDMI analyzer.What you do get on a more sane level are HDMI cabel testers. The very cheap ones are really just checking cable continuity. But since you already changed the cable they don't make sense for your problem. For around 30 Euro you get cable testers that give a rough indication of the presence of signals (http://www.ebay.com/itm/HDMI-Cable-Signal-Tester-HDMI-320-Master-Unit-New-/121025726025). However, it is still a gamble if their "opinion" about the HDMI signal allows to make a decision which of your two devices is at fault.Another alternative would be you try to borrow another TV or modern computer monitor with HDMI input from someone.

author: Mike Warren
author_rank: Unknown
timestamp: August 14, 2013, 06:10:57 am
content: Thanks for the reply. I guess I'll ask around and see if anyone has one I can borrow for a week or so.I miss analogue.

author: Psi
author_rank: Super Contributor
timestamp: August 14, 2013, 07:47:02 am
content: Tried moving the hdmi plug from side to side up/down?I've seen badly soldered hdmi connectors cause the image to change color and do various other weird things.Another thing i would try is a 110/230V mains filter on your gear.It could be a powerline spike getting onto the hdmi line somewhere and causing errors which trigger a restart.

author: Mike Warren
author_rank: Unknown
timestamp: August 14, 2013, 09:21:49 pm
content: Thanks. I have tried wiggling the plugs at both ends. Anyway, I've found a TV that I can borrow for a week or so. I just hope it plays up quickly or my wife will be complaining about the small screen size.

author: MasterOfNone
author_rank: Regular Contributor
timestamp: August 14, 2013, 10:26:44 pm
content: Quote from: Mike Warren on August 14, 2013, 09:21:49 pmNow if you could get hold of an HDMI splitter and connect both TVs to the Hard Disk Recorder (at the same time) you would really be able to identify the source of the problem. At the moment if it’s the TV that is faulty you could be watching a lot of the small TV before you decide it definitely should have happened by now. But if it’s the HDR you might be in luck and it might happen quickly.With two TVs connected you would be able to see your TV blank while the other stays on (if your TV is faulty), or both TV’s blank if the HDR is faulty. Of course if you don’t see the problem on either TVs then the splitter might have done something to the signal to solve the problem.

author: Mike Warren
author_rank: Unknown
timestamp: August 15, 2013, 03:05:13 am
content: Quote from: MasterOfNone on August 14, 2013, 10:26:44 pmThanks for the reply. I'll add one to the Altronics order I'm about to place. Should be a useful device to have around anyway.

author: atunguyd
author_rank: Contributor
timestamp: August 15, 2013, 07:00:59 am
content: I work for a fairly large manufacturer of set top boxes for the pay TV industry, I can tell you that what other have said about HDMI compatibility is true - the spec is massive and getting compliance is a really hard thing to do.That is further compounded by the fact that many of the cheaper manufacturers of TV's just do their own thing anyway. Problem is that even cheap TV's are more expensive than source devices like set top boxes so the consumer has the mindset of "well my $1000 TV must be right because it is not working with my $100 set top box".While we still do HDMI compliance testing we also do a procedure that we call the "HDMI plugfest" where we arrange for a team to go into one of the local major shops one evening and plug our set top box into every TV that they have on display to test if they in fact work with that model. It is a real pain and very costly but is the only way we have managed to try to get our box working with as many TV's as possible. We have even found major brands like Panasonic that would not work and upon further investigation found that they are not compliant - in one case the TV would ignore the signals to tell it what color space we were transmitting in.

author: atunguyd
author_rank: Contributor
timestamp: August 15, 2013, 07:07:57 am
content: Quote from: MasterOfNone on August 14, 2013, 10:26:44 pmUnfortunately this test is flawed because HDMI is not a one way communication. When you plug a TV into a device the TV and the device negotiate between them what resolution to use as well as other information like what color space the TV can support etc. The device then sends the agreed upon signal to the TV. The following problems could occur in your test above:1. Your TV would end up getting a completly different signal to the one it normally gets when it is the sink connected to your source.2. When an anomaly occurs on your TV the other TV might re-negotiate the link which will cause the video and audio to drop out and reconnect, this would make you think that the source was the problem when in fact it was still your TV it just cause teh second TV to also drop out for a second.Keeping the above in mind you can see that with the test proposed without more information any outcome can neither prove the TV being at fault or not.

author: MasterOfNone
author_rank: Regular Contributor
timestamp: August 15, 2013, 07:38:51 am
content: Quote from: atunguyd on August 15, 2013, 07:07:57 amI think you're right. That test only works on analogue signals, with the handshaking on HDMI the results would be inconclusive. Hopefully Mike has enough time to cancel that order.

author: atunguyd
author_rank: Contributor
timestamp: August 15, 2013, 09:47:00 am
content: If he tries a splitter it might not be a total waste - It might just remove the symptoms which is what Mike really wants doesn't he?Debugging HDMI issues is a real pain and you have to throw out all the analogue type thinking before you go into it. Add HDCP to the mix and it goes from bad to worse!

author: tom66
author_rank: Super Contributor
timestamp: August 15, 2013, 09:52:36 am
content: HDMI carries audio with the video signal, during the blanking time. It is unlikely a fault in the cable would only affect audio, and not video. I would say that it is probably a small incompatibility between the source and TV which may not be resolved until the source, or TV, are replaced.

author: jc101
author_rank: Frequent Contributor
timestamp: August 15, 2013, 10:53:06 am
content: First I'd check for any FW updates for the player or TV, the description sounds like an HDCP handshake failing and re-trying, often this is simply software. I see it a fair bit in the AV world, when running projectors from various sources and switching, some source kit will blank randomly or cough when running. As said earlier in the thread, some kit doesn't play nicely with others, but that often gets sorted with updates.Looks like the current player is 1.13 or 1.14 depending on region...http://panasonic.jp/support/global/cs/bd/download/pwt520/Sony TV softwarehttp://esupport.sony.com/US/p/model-home.pl?mdl=KDL55EX720&template_id=1&region_id=1&tab=download#/downloadTabWorth a try anyway....

author: Mike Warren
author_rank: Unknown
timestamp: August 15, 2013, 12:57:35 pm
content: Quote from: atunguyd on August 15, 2013, 09:47:00 amYep. If adding the splitter fixes the problem, then I'll be happy. If not, it will be a useful widget to have around.

author: Mike Warren
author_rank: Unknown
timestamp: August 15, 2013, 12:58:58 pm
content: Quote from: jc101 on August 15, 2013, 10:53:06 amBoth the TV and DVR are connected to my network and [I think] update themselves when needed.

author: Mike Warren
author_rank: Unknown
timestamp: August 15, 2013, 01:00:50 pm
content: Quote from: tom66 on August 15, 2013, 09:52:36 amAlways, both video and audio mute at the same time.

author: jc101
author_rank: Frequent Contributor
timestamp: August 15, 2013, 01:17:15 pm
content: Quote from: Mike WarrenThat does sound link HDCP or sync related. If you don't use it, you can always try turning off HDMI CEC - just in case there is some handshaking trying to happen in there which is failing, setting that off on the TV would do to test. (Sony call it BRAVIA link/control I think)I presume these HDMI cables are not too long (5m+)? I've found in installations over that is asking for trouble and would be looking at decent extenders.I'd check the FW revisions all the same, my TV or BR often don't update automatically. The Samsung TV has an option to do it, but it's off by default and doesn't seem to do it when enabled anyway.

author: Mike Warren
author_rank: Unknown
timestamp: September 24, 2013, 02:55:16 am
content: To finish this off, before I had a chance to test the splitter my wife talked me in to buying a surround sound system. The HDMI signals from both devices now feed through the amplifier and we have not had the fault since.So it looks like it was a compatibility problem.