HDMI stands for High Definition Multimedia Interface. To transfer the digital video signal from a source to a TV, the source must convert the signal from digital to analog, this results in some information loss.
However, an HDMI output can transfer a digital video source signal (such as from a DVD player) digitally, without conversion to analog. This results in a pure transfer of all of video information from the digital video source to a HDMI or DVI (via a connection adapter) equipped TV. In addition, HDMI can transfer both video and audio signals.
HDMI can pass video resolutions from 480i up to 1080p. However, each manufacturer determines the parameters for what is to be transferred via HDMI in their components.
HDMI can be implemented on Televisions, AV Receivers, DVD Players, Blu-ray Disc Players, HD-DVD Players, HD Cable Boxes, and HD Satellite Boxes.
HDMI also includes provisions for HDCP (High Definition Copy Protection). This allows content providers to prevent their programming from being illegally copied.
HDMI can be adapted to DVI (Digital Video Interface), via adapter cable or connector. However, the device that has the DVI connection must be HDCP enabled for the signal transfer to work.
There are several versions of HDMI that have been developed over the years. In each case the physical connector is the same, but the content characteristics have evolved. Depending on when you purchased an HDMI-enabled component (HDTV, DVD player, Blu-ray Disc player, etc...) would determine what HDMI version you have. All newer versions are backwards compatible. You can still use newer versions of HDMI with components equipped with older versions, you just won't be able to access the all the features of the newer version(s).
IMPORTANT NOTE: Although the various versions of HDMI are able to access the features listed, not all home theater components touted as being compliant with a specific version of HDMI will automatically provide all those features. Each manufacturer can pick-and-choose what features from their selected version of HDMI they want to incorporate into their products.
HDMI 1.0 - HDMI 1.0 combines a digital video signal (standard or high-definition) with a two-channel audio signal over a single cable, such as between an HDMI-equipped DVD player and Television.
HDMI 1.1 - This version adds the ability to transfer not only video and two-channel audio over a single cable, but also added the ability to transfer Dolby Digital, DTS, and DVD-Audio surround signals, as well up to 7.1 channels of PCM audio.
HDMI 1.2 - This version of HDMI adds the ability to transfer SACD signals in digital form from a player to a receiver.
HDMI 1.3 - This version includes improvements in both audio and video capability. With the advent of Blu-ray Disc and HD-DVD, version 1.3 adds the ability to transfer the digital bitstreams for the new high resolution audio formats: Dolby Digital Plus, Dolby TrueHD, and DTS-HD.
HDMI 1.3a - In addition to the above audio improvements, HDMI 1.3 and 1.3a increase the amount of video bandwidth that can be transferred from a source to a display. This means, that in addition to the standard 24-bit color depth we are used to, HDMI 1.3 and 1.3a have the ability to transfer color depths up to 48-bits, and can accommodate resolutions much higher than the 1080p resolution standard that is in use today.
HDMI 1.4 - HDMI version 1.4 adds practical enhancements for HDMI connectivity. If home theater components, such as HDTVs, Blu-ray Disc players, and Home Theater Receivers, are HDMI 1.4 enabled, one or more of the following features can be implemented:
1. HDMI Ethernet Channel: This adds internet and home network connectivity to HDMI. In other words, both Ethernet and HDMI functions are available within a single cable connection.
2. Audio Return Channel: This may be the most practical application of HDMI 1.4. What this feature provides is a single HDMI connection between a TV and a home theater receiver that can not only pass audio/video signals from the receiver to the TV, but also pass audio originating from the TV's tuner to the receiver. In other words, when listening to audio accessed by the TV's tuner, you don't need a separate audio connection going from the TV to the home theater receiver.
3. 3D Over HDMI: HDMI 1.4 is designed to accommodate 3D Blu-ray Disc standards, with the capacity of passing two simultaneous 1080p signals using one connection. NOTE: An update (HDMI 1.4a) also incorporates additional 3D TV Broadcast, Cable, and Satellite formats.
4. 4Kx2K Resolution Support: Although the current high definition standard for consumer equipment tops out at 1920x1080 (1080p), HDMI 1.4 can accommodate future 3840x2160 and 4096x2160 high definition pixel resolutions (limited to 30hz frame rate).
5. Expanded Support For Color Spaces: This allows better color reproduction when displaying digital still photos from HDMI-connected Digital Still Cameras.
6. Micro HDMI Connector: Just as mini-USB is employed with portable digital devices, a new "Micro HDMI" Connector is much smaller connector that can still supports up to 1080p resolutions for portable devices. This is very practical for video camcorders, digital still cameras, and portable digital video playback devices.
7. Automotive Connection System: With the increase of in-car digital audio/video devices, HDMI 1.4 can handle the more demanding vibration, heat, and noise that may affect the quality of audio and video reproduction.
1. Expands the 4K (2160p) resolution compatibility of HDMI 1.4/1.4a to accept either 50Hz or 60Hz frame rates (maximum 18 Gbps transfer rate with 8 bit color).
2. Can accept up to 32 simultaneous channels of audio to accommodate future more-immersive surround sound format requirements.
3. Can accommodate up to a 1,536 kHz audio sampling rate to accommodate development of higher resolution audio formats.
4. Capability to send two independent video streams for viewing on the same screen.
5. Capability to send up to four separate audio streams to multiple listeners.
5. Support for the native 21:9 (2.35:1) aspect ratio.
6. Dynamic Synchronization of video and audio streams.
7. Expansion of HDMI-CEC capabilities.
For consumers that have components that only feature HDMI versions 1.0 through 1.3, you won't be able to access any added version 1.4, 1.4a, or 2.0 features, but you will still be able to use future 1.4/1.4a/2.0 enabled components with your current HDMI 1.0 to 1.3 components, you just wont have access to the newly added features (depending on what the manufacturer actually incorporates into a specific product). In other words, don't raise your arms in the air in frustration, fall into the depths of despair, or start planning a garage sale in order to get rid of your old HDMI equipment - if your components continue to work the way you want them too (for instance, if you don't need 3D or 4K HDMI features), you are OK - the choice to upgrade is up to you.
The Future of HDMI
As you upgrade and purchase new audio and video components, you will notice HDMI becoming more of a standard connection option with increasing capabilities. Eventually, the cable jungle behind your home theater system will disappear, as all the audio and video cables are reduced to one HDMI cable between each component for both audio and video. This is great news for consumers, but bad news for cable manufacturers. However, cable manufacturers seem to have an answer for this dilemma; have you noticed how much more expensive HDMI cables are?
NOTE: As of January 1st 2012 (with the exception of the term HDMI 2.0) references to HDMI ver numbers on new products are to be eliminated - Read Official Announcement.
For the purpose of communicating HDMI cable features to consumers that are now five cable categories: HDMI Standard, HDMI Standard with Ethernet, HDMI Standard Automotive, HDMI High Speed, and HDMI High Speed with Ethernet. For details on each category, refer to the Official "Finding The Right Cable" Page at HDMI.org.