采纳者外联网 Adopter Sign In

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.

Category:
OR
Filter by keywords.

Q. Do I need a separate audio cable if my if my HDMI output is a physical DVI (DVI to HDMI adapter) port is not a true HDMI port?
Digital Visual Interface (DVI) is a video interface standard designed to maximize the visual quality of digital display devices such as flat panel LCD computer displays and digital projectors. Because DVI is a video-only standard, a graphics card with DVI port, even one with a DVI-HDMI adapter sends uncompressed digital video data to a display but does not send audio.Return to top

Q. Do I need a different cable for a TVs that have the higher 120MHz refresh rate?

You do not need a different cable. The increased refresh rate is happening inside the TV so the cable itself is not required to carry additional bandwidth in this case.

Return to top

Q. Does HDMI support Closed Captioning?
Close Captioning

The evolution from analog to digital TV has added some complexity to Close Captioning (CC). With one standard way of broadcasting/transmitting, decoding and displaying content NTSC or PAL, depending on region, analog TV made enabling CC fairly easy across CE devices since the TV was able to do all the CC decoding.

With the advent of digital TV and the introduction of digital HDTV services (cable, satellite, etc.) the responsibility of decoding CC has been taken away from the TVs and put into the various Set Top Boxes (STB) that are required for the majority of the digital HDTV services. Additionally, these STBs now have different ways of enabling CC making it complicated and creating confusion for consumers. All set-top boxes are required to support CC, however the implementation of CC can vary from one product to another. Enabling CC on a specific set-top box can be simple, or more difficult, depending on the implementation.

HDMI LA recommends contacting your TV service provider (cable, satellite, etc.) for the correct way to switch on its CC feature as a first step to resolve this issue. The second step is to contact the manufacturers directly for the correct way to enable the CC feature within your product.

HDMI and Close Captioning

Closed Captioning (CC) works differently with digital connections (HDMI, DVI, etc.)

How old analog CC worked:
Source always sent CC information to the TV and the TV controlled whether the CC was displayed or not via the TV's remote (CC button).  The CC button on the TV only controls CC for analog connections (S-Video, Composite, Component) or Over The Air tuners (ATSC digital or NTSC analog)
 
How CC works in HDMI and other digital connections:

The TV remote's CC button does not enable/disable CC on HDMI sources.  To enable CC, the user must enable it at the source either through a source remote control key (i.e. CC button) or by going through the setup menu of the source.  The source will then combine the video content with the CC information and output that (video + CC) via HDMI to the TV.
 
The CC rendering is done at the source and not at the TV as it was with analog connections.  For example, with a typical cable box the CC is enable by going to the cable box setup menu and not the TV remote's CC button.  The TV remote's CC only controls the analog CC and does not control the CC for each of the HDMI source devices.  CC must be enabled from each of the individual HDMI sources.

Exact steps to enable CC varies between manufacturers so please contact the source manufacturer for instructions.


Return to top

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.

Return to top

Q. What types of video does HDMI support?

HDMI has the capacity to support existing high-definition video formats (720p, 1080i, and 1080p/60). It also has the flexibility to support enhanced definition formats such as 480p, as well as standard definition formats such as NTSC or PAL. Version 1.3 of the HDMI specification has increased bandwidth capability to offer even higher resolutions (1440p) and increased video quality to existing HD resolutions (for example, 1080p with increased color depth, or Deep Color).

Return to top

Q. 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.

Return to top

Q. 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.

Return to top

Q. What is HDMI’s new Deep Color capability?

The new Deep Color capability lets manufacturers build devices allowing consumers to enjoy billions of colors with incredible visual clarity and detail. HDMI 1.3 supports 10-bit, 12-bit and 16-bit RGB color depths and color space, an upgrade from the 8-bit maximum resolution in previous versions of the HDMI Specification.

Return to top

Q. As more and more devices converge, is HDMI an interface that can accommodate convergence between the PC and CE?

Absolutely. HDMI was developed using the same technology as DVI (Digital Visual Interface), the digital connection standard for the PC environment. So, HDMI is fully compatible with all DVI-enabled PCs (since HDMI offers both audio and video over one cable, and DVI carried only video, DVI-HDMI connectivity requires a separate audio cable).

HDMI enables PCs to deliver premium media content including high definition movies and multi-channel audio formats. HDMI is the only interface enabling connections to both HDTVs and digital PC monitors implementing the DVI and HDMI standards – fully compatible with the hundreds of millions of DVI displays already in the market.

Return to top

Q. Are there any compromises in using HDMI as a replacement for DVI?

No only are there no compromises, but HDMI provides much more than DVI. Both HDMI and DVI are able to transmit uncompressed, HD video signals. However, HDMI also transmits audio so that both audio and video signals are transmitted over a single cable. HDMI also offers devices CEC functionality (Consumer Electronics Control), the optional command set that allows users to control devices with a single remote.

Return to top

Q. What is the cost of upgrading a PC system from DVI to HDMI?

There are several options. The lowest cost would be to add a basic PCI Express HDMI Graphics card for approximately US$100. Higher end graphics cards, however, can offer better performance in certain applications. For example, for around $US400, manufacturers are offering a high-end graphics card with built-in processing power so that as the user watches a movie, for example, he or she can also use the processing power of the computer to do other work. The processor on the graphics card is doing the required processing to play the movie, leaving the PC’s CPU free to perform other applications. As well, some graphics cards have their own audio controller and do not require an external S/PDIF input.

If you intend to use your PC to render video on a large TV, make sure your HDMI graphics cards incorporates high-quality video processing. ATI Avivo™ or nVIDIA’s PureVideo™ HD2 technology are two such offerings from these companies.

Return to top

Q. What can a PC with HDMI do that cannot be done with DVI?

HDMI offers both audio and video over one single cable making set-up and cabling much simpler. With this convergence interface, HDMI offers a simple way for PCs to connect to a TV.

Return to top

Q. What is the DDC?

DDC stands for Display Data Channel. In a video system, the vast majority of information flow occurs from a source to a sink where the video and/or audio travels. DDC provides a back channel from the sink to the source to indicate events like hot-plug. In addition, it allows the sink to communicate its display output capabilities back to the originating source device. Without this feature, devices like graphics cards or DVD players would have to guess at what video/audio formats a display would like to see. The DDC specification is currently at rev DDC-CI and is available from VESA (www.vesa.org).

Return to top

Q. What is EDID?

EDID stands for Extended Display Information Data. This is the data contained (usually in a small EEPROM) on each DVI display or HDMI sink. There may be as many as one EDID per DVI or HDMI input.

The source device checks the display’s DVI or HDMI port for the presence of an EDID prom and uses the information inside to optimize the output video and/or audio format. The EDID data structure can be for either VESA PC devices or for CEA-861B E-EDID (Enhanced EDID) devices. All sink devices compliant to the DVI or HDMI specification must implement EDID.

An EDID PROM is used only in sink devices. An EDID PROM sits on the DDC channel and uses a 2-wire I2C bus (part of the DDC specification from www.vesa.org) to communicate from the sink to the source. The EDID PROM contains information about the sink that it resides in. Its job is to communicate the preferred (or supported) video and audio formats and resolutions to the originating source. As an example, when a DVD player is powered on, it reads the EDID from an attached HDTV. The HDTV will have in its EDID contents that it is a Samsung 17” LCD panel that supports native resolution of 1280x1024 pixels, but can also support 480p, 720p and 1080i video modes. The EDID may also say that the TV is an HDMI device and has 2-speakers. The DVD player would compare this information with what it can put out of its HDMI port, then set itself to send 1080i with 2-channel stereo to the HDTV.

Return to top

Q. What is the difference between EDID and E-EDID?

EDID was formed as a standard to help PC monitors report their capabilities. E-EDID is an extension of the EDID specification used traditionally by consumer electronic devices to illustrate more advanced features.

For example, PC monitors generally do not support audio, so a traditional EDID structure would not account for this, whereas an E-EDID would.

The requirements for a consumer electronics device’s E-EDID are available in the CEA- 861B specification (www.ce.org).

The requirements for a PC device EDID are available from VESA (www.vesa.org).

Return to top

If you didn't see the answer you needed, please help us expand our Knowledge Base by asking your question here.