What is it
A digital interface for both audio and video in a single cable, born as an evolution of the DVI (who transferred only video), with a connector of reduced dimensions and a high data transfer capability that supports resolutions up to 4K (4096 horizontal pixels) and 32-channel audio and a bandwidth of up to 18Gbit / s (latest version 2.0 presented at IFA in Berlin a few days ago). The first version of HDMI was very similar, in terms of features, the DVI standard, and as a band and as video resolutions (in fact the connection HDMI is backward-compatible with DVI connection), but it has added support for audio and support for HDCP content protection.
Main versions of the HDMI:
- HDMI 1.0 and HDMI 1.1
- Bitrate 4,9Gb / s
- resolution up to 1080p
- up to 8 audio channels
- connector of reduced size to about 14x4mm (Type A)
- HDMI 1.2 and HDMI 1.2a (2005)
- added support Super Audio CD
- CEC function (control devices)
- HDMI 1.3, 1.3a 1.3b 1.3c (since 2006)
- doubled the bandwidth to 10.2Gb / s
- necessary to review the quality of cables
- classification in Category 1 (for cables up to the band of 4.9Gb / s) and Category 2 (for cables compliant with the new resolutions)
- support color depth
- support Dolby TrueHD and DTS-HD Master Audio
- New HDMI mini connector (Type C)
- doubled the bandwidth to 10.2Gb / s
- HDMI 1.4 and HDMI 1.4b (since 2009)
- new resolutions 4K and 2K
- support 3D
- adding the ability to transfer data to Ethernet (HEC) and Audio Return Channel (ARC), with the use of cables compatible with this standard (this function is optional and not required to maintain compatibility with the previous Cable)
- New micro HDMI connector (Type D) and Automotive lockable connector (Type E)
- HDMI 2.0 (presented at IFA 2013)
- bandwidth up to 18Gb / s
- 4k support up to 60fps
- support 21: 9 format and improved 3D support
- support 32 channels of audio
- HE-AAC audio support and DRA
Classification of cables
All cables in the market, both old and new, are compatible with any version of HDMI, because they are all very similar to each other as electronic structure, so they can operate by HDMI version 1.0 to version 2.0. Between the cables, there are of different lengths and of different standard to figure out up to that band can arrive and if it is possible to have more functions in certain cables compared to other: this means that, to connect two devices in FullHD mode is sufficient a standard HDMI cable Standard, although both have HDMI 1.4 connections.
- HDMI cables Standard ("Category 1" in the first classification)
- They are fine for most applications (eg DVD, SkyHD or other decoder), are tested for HD resolutions 720p or 1080i, are cheaper and can be found in various sizes (even beyond 10m)
- NOTE: Standard an HDMI cable, in combination with a repeater or equalizer High Speed, can even work in high-speed mode (generally more economic solution than buying a cable High Speed for lengths above to 10mt)
- High-Speed HDMI cable ("category 2" in the first classification)
- This is of special cables, tested up to 1080p and beyond (advanced technologies: color deep, 4K, 3D), have a higher bandwidth and, therefore, are recommended use with Blu-Ray players or other devices latest generation.
- Cables HEAC (with Ethernet Channel and Audio Return Channel)
- They offer all the benefits of normal HDMI cables Standard / High Speed plus a dedicated channel for data (known as HDMI Ethernet Channel) and a dedicated channel for the return audio (Audio Return Channel); this type of solution is useful for reducing the amount of cables, but it is not mandatory to use these cables.
Channels HEC ARC or work only with equipment compatible with the HDMI 1.4 protocol, whether they have internet access or require a return audio connection (such as a home-theater connected to a TV which are both HDMI 1.4).
In the absence of these cables, you can always use the HDMI cables Standard supported by Ethernet cables and / or Optical cables for the audio, the result will be exactly the same.
Indicative table of the testing of HDMI cables with a length and section
| Test HDMI Cables | Standard cat1 | High Speed cat2 | FullHD 1080p test | FullHD 1080p Eq test |
|---|---|---|---|---|
| 22AWG | 15m (12) | 10m (8) | 26mt | 35mt |
| 24AWG | 10mt | 6mt | 23mt | 35mt |
| 26AWG | 7m (8) | 5mt | 20mt | 33mt |
| 28AWG | 5m (6) | 4mt | 15mt | 23mt |
| 30AWG | 4mt | 3m | 5mt | - |
| 32AWG | 1,5mt | 1,5mt | - | - |
How to read the table:
- the lines refer to the section of the conductors in the cables (HDMI example, the cable of 10mm in diameter is a 24AWG, while the 7mm is a 28AWG and 30AWG 5mm is a);
- The first two columns refer to the certification standard (category 1) or High-Speed (category 2), and lengths for certification are very strict to ensure the operation, while the last two columns refer to the maximum lengths in the functional tests in mode FullHD 1080p (the last column, in particular, with the use of an equalizer at the end of the HDMI cable);
- lengths refer to the latest generation of HDMI devices (protocols HDMI 1.3 and HDMI 1.4), while the measurements in parentheses indicate that, if one of the two devices (or both) is HDMI 1.2, the length reached is slightly different.
Note: HDMI cables from 24AWG are generally up to 25 meters, according to this table their operation would be guaranteed only up to 10m Standard (or up to 6 meters High Speed), being therefore beyond the limits, it is likely to require the use of an equalizer if the functional test should give negative results.
