. Never before have four simple letters caused so much pain for so many custom integrators.
When the technology was introduced back in 2002, it seemed to be the long-awaited one-wire solution to the potential rat’s nest of wiring that always hampered growth of the high-definition signal transmission in residences. And for most consumers with simple setups, HDMI has been a godsend.
But for custom installers who are often asked by clients to “break all the rules” with lengthy wire runs and multiple displays, the one-wire solution became one big headache.
At CEDIA Expo 2011
, the HDMI Licensing Group held an all-day symposium to discuss “all things HDMI.” Among the hottest topics were basic and advanced troubleshooting tips, solving real-life situations in some cases. See the highlighted boxes in this article that show eight real scenarios from the AVS Forum website and their likely solutions from integrators. Use it as a fun quiz for your staff.
Also, continue to refer to our resident HDMI guru Jeff Boccaccio, who recently analyzed the inside jacket of HDMI cables
Basic HDMI Troubleshooting Tips
Avoid the Need to Troubleshoot
Prequalify all the equipment in the home and that you procure in your lab before you start the job.
Consider the Origin of the Problem
Determine if the existing HDMI system has ever worked. If so, what changed? Take careful notes.
Make One Change at a Time
Make only one switch at a time to limit the variables. Again, take careful notes.
Configure or “reduce” the system to the simplest configuration that still exhibits the symptom.
Substitute suspect devices or components with known-good devices or preferably with test equipment that can emulate sources and sinks with other convenient control functions.
Disable CEC and HDCP if possible. Disabling HDCP will immediately tell you if the problem is related to that.
Use the diagnostic procedure that provides greatest insight and is easiest to conduct.
Problem 1: No Audio
A system that consists of a DVR via HDMI to an A/V receiver (AVR) via HDMI to a projector and there is no audio?
The probable cause is that the AVR is not substituting its audio block into EDID. For the integrator, the short-term resolution is to bypass the AVR; the long-term solution is to replace the AVR.
Problem 2: No Picture
There is no picture following standby. The client is having a problem with his media server and HDTV. Once the TV goes to standby, the media server and HDTV will not handshake properly and he gets the infamous green screen instead of video. The only solution that works is literally unplugging the HDMI cable from the media server and re-inserting it.
The probable cause is that the media server not asserting hot plug. Replace the media server or put a “fix it” device between media server and HDTV.
Problem 3: Intermittent Flashing
Using HDMI for all connections, the setup is a set-top box to a DVR to an AVR to an HDTV, which results in intermittent flashing. However, when the setup is altered to DVD/Blu-ray to AVR to HDTV (all via HDMI), the flashing disappears.
The probable cause is an HDCP authentication failure. The STB is not processing the A/V receiver’s HDCP repeater bit. The resolution is to swap out STB and DVR.
Problem 4: Pixel Errors or "Sparkles"
Sparkles occur in the family room display from the STB.
This is the often the most difficult problem to isolate the cause. A partial list of possible causes includes:
- Excessive dielectric loss through HDMI cable or HDMI extender or repeater device
- Excessive skew on the TMDS pairs
- Poor quality HDTV (poor equalization)
- Pre-HDMI 1.3 source without pre-emphasis
There is a sequence of tests that need to be conducted to isolate the problem. First, conduct a cable/repeater test with the objective of determining if the HDMI cables to and from the matrix switch and the switch itself are passing good video. If this test passes then the most likely cause is the Extender.
Second, run a test on the Cat extender and then the Cat 5 cable itself by swapping them out. If the tests fail then you should perform individual tests on each cable. If one fails, replace it. If they do not fail, replace the matrix switch.
Third, conduct a cable/repeater test or frame test to determine if the HDMI cables to and from the matrix switch, the switch itself and the extender are passing good video. If you cannot run the cable/repeater test, then run the frame compare test.
Pixel errors or “sparkles” are caused by various things, including:
- Intra-pair skew - The loss within one of the TMDS pairs. Typically results from differential lengths of the twisted pair
- Dielectric loss - Distortion or “smear” of the signal due to attenuation of high frequencies
Diagnosing physical layer problems requires very expensive equipment; therefore, diagnosing such problems is by inference. The general symptom of this problem is characterized by sparkles or intermittent snow. The symptoms of some physical layer problems can be similar to HDCP protocol layer problems.
Problem 5: HDMI Blinking
When the system is set up from the set-top box source via HDMI to an AVR, and then HDMI to an HDTV, there is annoying blinking for both video and audio.
However, the system works fine when the AVR is bypassed and content is sent directly from the STB to the TV. Also, there is no blinking when watching content from the DVD player via the AVR using HDMI to the TV. Updating the TV’s firmware did not help.
The probable cause is an HDCP authentication failure. The STB does not support repeaters or does not parse HDCP repeater bit. The resolution is to swap out the STB.
Problem 6: Flashing Video for 2 Seconds
In a setup (with HDMI as the connector) that is DVR to AVR to HDTV, the picture is dropping for two seconds. The AVR manufacturer says it’s the DVR [fault], while the cable provider says the homeowner needs to use component video connections from the DVR to the AVR.
The probable cause is another HDCP authentication failure. The STB is not processing the A/V receiver’s HDCP repeater bit. The resolution is to swap out the STB.
Problem 7: Pink Tint TV
In a setup with a satellite set-top box (STB) connected via HDMI to an HDTV, there is sometimes a pink tint on the TV. When the connection is changed to component, the tint goes away. Also, if another brand of TV is connected, the pink disappears. Replacement of the DVR also did not help. The satellite provider has sent a service team and they did not have any answers.
The probable cause is a mismatch in color space. The source STB is sending YCbCr to an HDTV in RGB mode. There could be problems with the EDID or AVI InfoFrame. The source STB is not reading EDID properly or is sending incorrect InfoFrame. Consider replacing STB source.
Problem 8: Audio Dropout
In a setup using HDMI connectors from an STB to AVR to HDTV, there is digital audio dropout. Similarly, the system only picks up analog audio from the STB directly to the HDTV, and from the STB via optical cable to the AVR.
There are two possible causes. First, the audio buffer is being overrun by audio sample packets. Second, the audio InfoFrames are missing. The resolution is to swap out the STB.