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.

What is the most common compatibility problem among devices with HDMI connections?
The most common compatibility problems have to do with HDCP. Probably the most common failure is the lack of an HDCP repeater function or failure to perform the authentication reliably in all types of usage scenarios. We are increasingly seeing HDCP becoming less and less of a problem as manufacturers iron out the kinks in later generation devices and as cable operators download upgraded firmware to their set-top boxes. In addition, as of November, 2006, the HDMI Founders required all HDMI devices implementing HDCP to undergo a new mandatory compliance testing program of the HDCP functions. This is based on the HDCP Compliance Test Specification.

What is HDCP?
HDCP stands for High Definition Content Protocol and is a copy protection scheme to eliminate the possibility of capturing content sent digitally from the source to the display. The format is designed by Intel with help of Silicon Image, the company that distributes the chips to enable the scheme, HDCP enables a secure connection between devices such as DVD players and HDTV set-top-boxes using an authentication and key exchange procedure before video and audio is presented. If your video source sends DVI or HDMI™ signal that is HDCP encrypted, your display must also be HDCP compliant. Otherwise, the signal will result in what we call "sparkles" or snow. All PureLink DVI and HDMI Switching Systems are HDCP compliant. Be sure to check HDCP compliance when you purchase any AV equipment.

Some cable TV set-top boxes with HDMI outputs don't deliver a picture to displays with HDMI inputs. What is the problem, and is there a solution?
In some cases, the set-top box software does not activate or support the HDMI port. In other cases, cable TV set-top boxes don't work correctly when used in conjunction with an A/V receiver (but will typically function correctly when connected directly to a TV or monitor). Investigation of some of these devices reveals that this is caused by an error in the way these set-top box devices implement HDCP. Specifically, some of those boxes do not support "HDCP repeaters" (devices that pass along the signal to another device) such as an A/V receiver or switch. We believe that this may be a problem in the initial versions of these products, and in some cases there is new firmware available that fixes this issue in HDMI (newer versions may already have this fix). We have been actively working with manufacturers to resolve these problems. We suggest that users contact their cable operator and request the new software to address these issues. As noted above, cable operators are increasingly downloading the available firmware upgrades required to fix this error.

If an HDMI accessory device (i.e. switch box, cable booster) does not have a dedicated power supply, is it still compliant and will it work?
An HDMI device that has active electronics should have a provision for external power in order to be compliant (e.g. a receptacle to allow the use of a standard power adapter, sometimes called a power "brick"). Here we are drawing a distinction between "active" devices that actually have some powered electronics, and "passive" devices, such as some switches (more on those later).
Some active devices, such as actively powered HDMI cables or in-line signal extender boxes, will by default attempt to power their electronics by taking power from the 5V line (+5V power) available on the HDMI connector. The HDMI specification requires all source devices to provide at least 55mA (milliamps) on the 5V line for the purpose of reading the EDID of a display. While 55mA is not enough current to operate most HDMI accessory devices (which typically require about 100 to 150mA), most source devices on the market today provide significantly more current on the 5V line than the HDMI specification requires. As a result, the vast majority of accessory devices can operate when interfaced with a source device that provides more than the required current (i.e. over 100-150mA) on the 5V line. However, manufacturers should provide a provision for their powered HDMI accessory devices to obtain external power, and consumers are encouraged to look for this external power provision when purchasing such products.
Looking to the future, not all HDMI devices may provide this much power over the 5V line. For example, as HDMI expands into more and more portable applications (cameras, camcorders, laptops, etc.), power consumption is often much more of an issue, and such devices may not power the 5V line with the > 100mA required by such "active" devices. Again, consumers should consider ensuring that their active HDMI accessory device purchases have a provision for external power for this reason.

What version of HDMI does a consumer need to view 1080p content?
HDMI has always supported 1080p resolution, starting from version 1.0 in 2002. However, as with many functions that HDMI enables (such as DVD-Audio and SACD), it is up to the manufacturer to choose whether to implement 1080p in the device. Some TV and device manufacturers have chosen not to implement 1080p in their products because 1080p content has not been widely available, and because changing the internal electronics of the device to support 1080p would increase cost.
Viewing 1080p resolution requires at minimum that the HDTV have a display supporting the 1080p pixel resolution. Today, many HDTVs use display technologies (such as PDP, LCD, and microdisplay screens) designed for 720p pixel resolution. In the past, some 1080p HDTVs supported only 720p or 1080i on the HDMI input, then perform video processing to up-convert the 720p/1080i signal to 1080p. This is now changing, as 1080p content is becoming increasingly available, and HDTVs fully supporting 1080p in the display and HDMI electronics became more popular in the market in early 2006. True 1080p HDTVs are currently offered in the market by a variety of TV manufacturers.

Do you need a new version of HDMI to play Blu-ray and HD-DVD content in high definition?
All versions of the HDMI specification support the ability to watch HD-DVD / Blu-ray content in high definition up to 1080p resolution. However, there may be non-HDMI reasons that prevent some devices from accessing content in high definition, including lack of HDCP support.

Are HDMI 1.0, 1.1 and 1.2 compatible with the next generation videogame consoles implementing 1080p and HDMI's new Deep Color capability?
The HDMI specification has supported 1080p content since version 1.0, and each new revision of the HDMI specification is fully backward compatible with previous revisions.
In June 2006, the HDMI Founders announced HDMI 1.3 and new capabilities to support Deep Color (up to 16-bit color RGB color) and new lossless audio formats (such as Dolby TrueHD and DTS-HD Master Audio). PCs and video game consoles in particular are expected to be capable of delivering content that takes advantage of HDMI's latest capabilities. When such sources are interfaced to older HDMI HDTVs, the source should automatically select the highest quality video and audio performance supported by the HDTV.

Does HDMI support Dolby 5.1 audio and high-resolution audio formats?
Yes. From the start, HDMI was defined to carry 8-channels, of 192kHz, 24-bit uncompressed audio, which exceeds all current consumer media formats. In addition, HDMI can carry any flavor of compressed audio format such as Dolby or DTS. (Such compressed formats are the only multi-channel or high-resolution audio formats that can be carried across the older S/PDIF or AES/EBU interfaces.) Additionally, most existing HDMI sources can output any compressed stream, and the newer sources can output uncompressed 6-channel, 96kHz audio from a DVD-Audio disk. There are A/V receivers on the market that can accept and process the 6- or 8-channel audio from HDMI.

Does HDMI support Dolby Digital, DTS, and high-resolution audio formats?
Yes. From the start, HDMI was defined to carry 8-channels of 192kHz, 24-bit uncompressed audio, which exceeds all current consumer media formats. In addition, HDMI can carry any currently available flavor of compressed audio format such as Dolby (including Dolby Digital EX 7.1, Dolby Digital Plus 7.1, Dolby TrueHD) or DTS (including DTS-ES 6.1 and DTS-HD Master Audio). Such compressed formats are the only multi-channel or high-resolution audio formats that can be carried across the older S/PDIF or AES/EBU interfaces. HDMI 1.3 adds additional support for new lossless digital surround audio formats Dolby TrueHD and DTS-HD Master Audio. Additionally, most existing HDMI sources can output any compressed stream, and the newer sources can output uncompressed 6-channel, 96kHz audio from a DVD-Audio disk. There are A/V receivers on the market that can accept and process the 6- or 8-channel audio over HDMI.

Is HDMI backward compatible with DVI (Digital Visual Interface)?
Yes, HDMI is fully backward compatible with DVI compliant devices. HDMI DTVs will display video received from existing DVI-equipped products, and DVI-equipped TVs will display video from HDMI sources. However, some older PCs with DVI are designed only to support computer monitors, not televisions. Consumers buying a PC with DVI should make sure that it specifically includes support for television formats and not just computer monitors.
Also, consumers may want to confirm that the DVI interface supports High-bandwidth Digital Content Protection (HDCP), as content that requires HDCP copy protection will require that both the HDMI and DVI devices support HDCP to properly view the video content.