Knowledge Base

The HDMI Licensing Knowledge Base is a library of current information about the HDMI standard. Select an appropriate category from the pull down below, or, you may use your own search terms to obtain results.

If your question involves a specific product, please contact the manufacturer directly. The HDMI Knowledge Base does not contain information about specific products.

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Q. Can I use HDMI to connect one from to another using wall plates?

You can connect from one room to another using wall plate connections. However, the quality of the wall plate can affect the transmission. Be sure to select an HDMI-compliant wall plate that fits your specific installation requirements.

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Q. What is the difference between Active HDMI and Passive HDMI?

There is no active or passive HDMI in the test specification. These terms apply to cables. Active cables have built-in electronics to enable long cable runs, and typically these cables require a power supply. These cables use active electronics to help push the signal farther than typical passive cables.

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Q. What are the advantages of HDMI connectivity over existing analog video interfaces such as composite, S-Video and component video?

Quality: Because HDMI technology is a digital interface, it provides the best quality of the video since there are no lossy analog to digital conversions as are required for all analog connections (such as component or S-video). The difference is especially noticeable at higher resolutions such as 1080p. Digital video will be sharper than component, and eliminates the softness and ghosting found with component. Small, high contrast details such as text bring this difference out the most.

Ease-of-use: HDMI combines video and multi-channel audio into a single cable, eliminating the cost, complexity, and confusion of multiple cables currently used in A/V systems. This is particularly beneficial when equipment is being upgraded or added.

Intelligence: The HDMI interface supports two-way communication between the video source (such as a DVD player) and the DTV, enabling new functionality such as automatic configuration and one-touch play. By using HDMI connectivity, devices automatically deliver the most effective format (e.g 480p vs 720p, 16:9 vs 4:3) for the display that it is connected to - eliminating the need for the consumer to scroll through all the format options to guess what looks best.

HD Content-Ready: HDMI devices supporting HDCP have the comfort of knowing they will have access to premium HD content now and in the future. HD-DVD and Blu-ray have delayed the activation of the image constraint token (a.k.a. content protection flag) with today’s HD movies to help minimize potential issues caused by the transition, but are expected to activate this in a few years, meaning future HD movies will then not be viewable at HD resolutions over unprotected interfaces such as analog component.

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Q. What is the advantage of using HDMI over existing audio interfaces such as analog RCA connectors and digital SPDIF (coax and optical connectors)?

Quality: HDMI maintains the audio in its pure digital form all the way to the amplifier. Analog audio connections are more prone to losses depending on the cabling and other electronics of the audio rendering device.  Compared to SPDIF connections, HDMI has significantly more bandwidth, allowing it to support the latest lossless audio formats such as Dolby TrueHD and DTS-HS Master Audio. These formats can not be supported over SPDIF connections due to their very high data rate requirements that exceed the capabilities of SPDIF. Please also see section on HDMI 1.3 for further details on Dolby TrueHD and DTS-HD Master Audio formats.

Ease of Use: HDMI combines video and multi-channel audio into a single cable, eliminating the cost, complexity, and confusion of multiple cables currently used in A/V systems. This is particularly beneficial when equipment is being upgraded or added.

Intelligence: HDMI supports two-way communication between the audio source (such as a DVD player) and the audio rendering device (such as an A/V receiver), enabling new functionality such as automatic configuration and one-touch play. By using HDMI, devices automatically deliver the most effective format (e.g Dolby Digital vs. 2 channel PCM) for the A/V receiver that it is connected to - eliminating the need for the consumer to scroll through all the audio format options to guess what is best and properly supported.

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Q. Does HDMI accommodate long cable lengths?

Yes. HDMI technology has been designed to use standard copper cable construction at long lengths. In order to allow cable manufacturers to improve their products through the use of new technologies, HDMI specifies the required performance of a cable but does not specify a maximum cable length. We have seen cables pass "Standard Cable" HDMI compliance testing at lengths of up to a maximum of 10 meters without the use of a repeater. It is not only the cable that factors into how long a cable can successfully carry an HDMI signal, the receiver chip inside the TV or projector also plays a major factor. Receiver chips that include a feature called "cable equalization" are able to compensate for weaker signals thereby extending the potential length of any cable that is used with that device.

With any long run of an HDMI cable, quality manufactured cables can play a significant role in successfully running HDMI over such longer distances.

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Q. How do I run HDMI cables longer than 10 meters?

There are many HDMI Adopters working on HDMI solutions that extend a cable’s effective distance from the typical 10 meter range to much longer lengths. These companies manufacture a variety of solutions that include active cables (active electronics built into cables that boost and extend the cable’s signal), repeaters, amplifiers as well as CAT5/6 and fiber solutions.

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Q. My HDMI cable sometimes falls out of the HDMI connector. Is anything being done to address this problem?

The combination of vertically-oriented connectors and heavy, thick-gauge cables appears to have the potential of causing the connector to fall out. In some cases, it is due to the usage of a cable with a non-compliant, large connector over-molding that prevents proper connector engagement. The HDMI Founders are actively investigating a locking connector option that would be backward compatible with existing Standard (Type A) connectors.

We have seen a few connectors that are out of spec (e.g., not the right size, too much over-molding, etc.), which led to compatibility issues and, in some cases, connector damage. However, in December 2005, we implemented a connector certification program to help ensure that all Adopters use compliant connectors.

Several manufacturers are now selling “port savers” – short, flexible sections of HDMI cable that easily bend at a right angle for applications where the HDMI cable requires a 90 degree bend directly out of the connector. Without these “port savers,” heavier cables can put undue pressure on the connector and the connectors can dislodge.

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Q. Can HDMI cables contribute to devices not working properly together?

The vast majority of image quality or interoperability issues with HDMI devices are related to the software (firmware) used for device communication and content protection, and have nothing to do with the HDMI cable. In particular, these issues are often caused by the software related to HDCP handshaking, or from devices improperly handling the device capability information read through HDMI (e.g. the device has an incorrect EDID, or an inability to properly read an EDID). It is fairly uncommon for the cable to be the cause of HDMI compatibility problems. In fact, the robustness of the HDMI specification has been verified by the fact that we have not found a compliant HDMI cable that is the root cause of HDMI playback issues with compliant devices.

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Q. How can I tell if a cable is an HDMI certified cable?

All HDMI products are required to be certified by the manufacturer as part of the HDMI Compliance Test Specification. However, there may be instances where cables bearing the HDMI logo are available but have not been properly tested. HDMI Licensing Administrator, Inc. actively investigates these instances to ensure that the HDMI trademark is properly used in the market. We recommend that consumers buy their cables from a reputable source and a company that is trusted.

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Q. What is the difference between a “Standard” HDMI cable and a “High-Speed” HDMI cable?

Recently, HDMI Licensing Administrator, Inc. announced that cables would be tested as Standard or High-Speed cables.

  • Standard (or “category 1”) HDMI cables have been tested to perform at speeds of 75Mhz or up to 2.25Gbps, which is the equivalent of a 720p/1080i signal.
  • High Speed (or “category 2”) HDMI cables have been tested to perform at speeds of 340Mhz or up to 10.2Gbps, which is the highest bandwidth currently available over an HDMI cable and can successfully handle 1080p signals including those at increased color depths and/or increased refresh rates from the Source. High-Speed cables are also able to accommodate higher resolution displays, such as WQXGA cinema monitors (resolution of 2560 x 1600).
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Q. Will my Standard cable work in High Speed applications?

Although a Standard HDMI cable may not have been tested to support the higher bandwidth requirements of cables rated to support high speeds, existing cables, especially ones of shorter lengths (i.e., less than 2 meters), will generally perform adequately in higher speed situations. The quality of the HDMI receiver chip (in the TV, for example) has a large effect on the ability to cleanly recover and display the HDMI signal. A significant majority, perhaps all, of the HDMI TVs and projectors that support 1080p on the HDMI inputs are designed with quality receiver chips that may cleanly recover the 1080p HDMI signal using a Standard-rated HDMI cable. These receiver chips use technology called “cable equalization” in order to counter the signal reduction (attenuation) caused by a cable. We have seen successful demonstrations of 1080p signal runs on a >50 ft. cable, and a 720p signal run on a >75 ft. cable. However, the only way to guarantee that your cable will perform at higher speeds is to purchase a cable that has been tested at the higher speeds and labeled as “High-Speed.”

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Q. What are the technical and branding requirements for cables?

All cables shall be labeled, both on the cable itself and on the front of the cable packaging, as one of the following:

  1. Standard HDMI® Cable
  2. Standard HDMI® Cable
  3. Standard Automotive HDMI® Cable
  4. High Speed HDMI® Cable
  5. High Speed HDMI® Cable with Ethernet

Each of these Cable Names is an implementation defined in the HDMI Specification. HDMI Adopters should refer to Section 4.1 of the HDMI Specification Version 1.4b, “Connectors and Cables,” for more information.

For consumers who want more information on selecting the right cable for your needs, please click here.

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Q. What is the current Cat 1, Type A maximum cable length?

15 meters for a AWG22, 12 meters for AWG24, and 10 meters for a AWG26. For Cat 2, the maximum seems to be 5-8 meters (more details later…)

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Q. What should I do for long cables length situations

Make sure you run a repeater if your cables length exceeds 10 meters.

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Q. Do HDMI cables get hot enough to cause a fire?

No. HDMI cables will not generate heat sufficient enough to cause a fire.

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Q. How can you tell the difference between a v1.2 and a v1.3 cable

You really can't. There are no technical differences in most Type A, Cat 1 cables. While there are real differences from a technical standpoint between a Type A, Cat 1 cable vs a Type A, Cat 2 cable, cosmetically, and most importantly, most standard 1080p applications do not need the Cat 2 cable.

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