The High-Definition Multimedia Interface (HDMI) is a licensable audio/video connector interface for transmitting uncompressed, encrypted digital streams. HDMI connects DRM-enforcing digital audio/video sources, such as a set-top box, a Blu-ray Disc player, a Personal Computer, a video game console, or an AV receiver, to a compatible digital audio device and/or video monitor, such as a digital television (DTV). HDMI began to appear in 2006 on prosumer HDTV camcorders and high-end digital still cameras.[1][2] It represents the DRM alternative to consumer analog standards such as RF (coaxial cable), composite video, S-Video, SCART, component video and VGA, and digital standards such as DVI (DVI-D and DVI-I).
General notes
HDMI supports any TV or PC video format, including standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It is independent of the various DTV standards such as ATSC, and DVB (-T,-S,-C), as these are encapsulations of the MPEG movie data streams, which are passed off to a decoder, and output as uncompressed video data on HDMI. HDMI encodes the video data into TMDS for transmission digitally over HDMI. Devices are manufactured to adhere to various versions of the specification, where each version is given a number, such as 1.0 or 1.3. Each subsequent version of the specification uses the same cables, but increases the throughput and/or capabilities of what can be transmitted over the cable. For example, previously, the maximum pixel clock rate of the interface was 165 MHz, sufficient for supporting 1080p at 60 Hz or WUXGA (1920x1200), but HDMI 1.3 increased that to 340 MHz, providing support for WQXGA (2560x1600) and beyond across a single digital link. See also: HDMI Versions. HDMI also includes support for 8-channel uncompressed digital audio at 192 kHz sample rate with 24 bits/sample as well as any compressed stream such as Dolby Digital, or DTS. HDMI supports up to 8 channels of one-bit audio, such as that used on Super Audio CDs at rates up to 4x that used by Super Audio CD. With version 1.3, HDMI now also supports lossless compressed streams such as Dolby TrueHD and DTS-HD Master Audio. HDMI is backward-compatible with the single-link Digital Visual Interface carrying digital video (DVI-D or DVI-I, but not DVI-A) used on modern computer monitors and graphics cards. This means that a DVI-D source can drive an HDMI monitor, or vice versa, by means of a suitable adapter or cable, but the audio and remote control features of HDMI will not be available. Additionally, without support for High-bandwidth Digital Content Protection (HDCP) on the display, the signal source may prevent the end user from viewing or recording certain restricted content. PCs with hardware HDMI output may require software support from Operating Systems such as Windows Vista. Linux currently supports video output through backward-compatibility with DVI. In the U.S., HDCP-support is a standard feature on digital TVs with built-in digital (ATSC) tuners, (it does not feature on the cheapest digital TVs, as they lack HDMI altogether). Among the PC-display industry, where computer displays rarely contain built-in tuners, HDCP support is absent from many models. For example, the first LCD monitors with HDMI connectors did not support HDCP, and few compact-LCD monitors (17" or smaller) support HDCP. The HDMI Founders include consumer electronics manufacturers Hitachi, Matsushita Electric Industrial (Panasonic/National/Quasar), Philips, Sony, Thomson (RCA), Toshiba, and Silicon Image. Digital Content Protection, LLC (a subsidiary of Intel) is providing HDCP for HDMI. In addition, HDMI has the support of major motion picture producers Fox, Universal, Warner Bros., and Disney, and system operators DirecTV and EchoStar (Dish Network) as well as CableLabs and Samsung.
Specifications
HDMI defines the protocol and electrical specifications for the signaling, as well as the pin-out, electrical and mechanical requirements of the cable and connectors.
Connectors
The HDMI Specification has expanded to include three connectors, each intended for different markets. The standard Type A HDMI connector has 19 pins, with bandwidth to support all SDTV, EDTV and HDTV modes and more. The plug outside dimensions are 13.9 mm wide by 4.45 mm high. Type A is electrically compatible with single-link DVI-D. A higher resolution version called Type B is defined in HDMI 1.0. Type B has 29 pins (21.2 mm wide), allowing it to carry an expanded video channel for use with very high-resolution future displays, such as WQSXGA (3200x2048). Type B is electrically compatible with dual-link DVI-D, but is not in general use. The Type C mini-connector is intended for portable devices. It is smaller than Type A (10.42 mm by 2.42 mm) but has the same 19-pin configuration.
Cable
The HDMI cable can be used to carry video, audio, and/or device-controlling signals (CEC). Adaptor cables, from Type A to Type C, are available.
Cable length
The HDMI specification does not define a maximum cable length. As with all cables, signal attenuation becomes too high at a certain length. Instead, HDMI specifies a minimum performance standard. Any cable meeting that specification is compliant. Different construction quality and materials will enable cables of different lengths. In addition, higher performance requirements must be met to support video formats with higher resolutions and/or frame rates than the standard HDTV formats. The signal attenuation and intersymbol interference caused by the cables can be compensated by using Adaptive Equalization. HDMI 1.3 defined two categories of cables: Category 1 (standard or HDTV) and Category 2 (high-speed or greater than HDTV) to reduce the confusion about which cables support which video formats. Using 28 AWG, a cable of about 5 metres (~16 ft) can be manufactured easily and inexpensively to Category 1 specifications. Higher-quality construction (24 AWG, tighter construction tolerances, etc.) can reach lengths of 12 to 15 metres (~39 to 49 ft). In addition, active cables (fiber optic or dual Cat-5 cables instead of standard copper) can be used to extend HDMI to 100 metres or more. Some companies also offer amplifiers, equalizers and repeaters that can string several standard (non-active) HDMI cables together.
HDMI and high-definition optical media players
Both introduced in 2006, Blu-ray Disc and HD DVD offer new high-fidelity audio features that require HDMI for best results. Dolby Digital Plus (DD+), Dolby TrueHD and DTS-HD Master Audio use bitrates exceeding TOSLINK's capacity. HDMI 1.3 can transport DD+, TrueHD, and DTS-HD bitstreams in compressed form. This capability would allow a preprocessor or audio/video receiver with the necessary decoder to decode the data itself, but has limited usefulness for HD DVD and Blu-ray. HD DVD and Blu-ray permit "interactive audio", where the disc-content tells the player to mix multiple audio sources together, before final output. Consequently, most players will handle audio-decoding internally, and simply output LPCM audio all the time. Multichannel LPCM can be transported over an HDMI 1.1 (or higher) connection. As long as the audio/video receiver (or preprocessor) supports multi-channel LPCM audio over HDMI, and supports HDCP, the audio reproduction is equal in resolution to HDMI 1.3. However, many of the cheapest AV receivers do not support audio over HDMI and are often labeled as "HDMI passthrough" devices. Note that not all of the features of an HDMI version may be implemented in products adhering to that version since certain features of HDMI, such as Deep Color and xvYCC support, are optional.
General notes
HDMI supports any TV or PC video format, including standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It is independent of the various DTV standards such as ATSC, and DVB (-T,-S,-C), as these are encapsulations of the MPEG movie data streams, which are passed off to a decoder, and output as uncompressed video data on HDMI. HDMI encodes the video data into TMDS for transmission digitally over HDMI. Devices are manufactured to adhere to various versions of the specification, where each version is given a number, such as 1.0 or 1.3. Each subsequent version of the specification uses the same cables, but increases the throughput and/or capabilities of what can be transmitted over the cable. For example, previously, the maximum pixel clock rate of the interface was 165 MHz, sufficient for supporting 1080p at 60 Hz or WUXGA (1920x1200), but HDMI 1.3 increased that to 340 MHz, providing support for WQXGA (2560x1600) and beyond across a single digital link. See also: HDMI Versions. HDMI also includes support for 8-channel uncompressed digital audio at 192 kHz sample rate with 24 bits/sample as well as any compressed stream such as Dolby Digital, or DTS. HDMI supports up to 8 channels of one-bit audio, such as that used on Super Audio CDs at rates up to 4x that used by Super Audio CD. With version 1.3, HDMI now also supports lossless compressed streams such as Dolby TrueHD and DTS-HD Master Audio. HDMI is backward-compatible with the single-link Digital Visual Interface carrying digital video (DVI-D or DVI-I, but not DVI-A) used on modern computer monitors and graphics cards. This means that a DVI-D source can drive an HDMI monitor, or vice versa, by means of a suitable adapter or cable, but the audio and remote control features of HDMI will not be available. Additionally, without support for High-bandwidth Digital Content Protection (HDCP) on the display, the signal source may prevent the end user from viewing or recording certain restricted content. PCs with hardware HDMI output may require software support from Operating Systems such as Windows Vista. Linux currently supports video output through backward-compatibility with DVI. In the U.S., HDCP-support is a standard feature on digital TVs with built-in digital (ATSC) tuners, (it does not feature on the cheapest digital TVs, as they lack HDMI altogether). Among the PC-display industry, where computer displays rarely contain built-in tuners, HDCP support is absent from many models. For example, the first LCD monitors with HDMI connectors did not support HDCP, and few compact-LCD monitors (17" or smaller) support HDCP. The HDMI Founders include consumer electronics manufacturers Hitachi, Matsushita Electric Industrial (Panasonic/National/Quasar), Philips, Sony, Thomson (RCA), Toshiba, and Silicon Image. Digital Content Protection, LLC (a subsidiary of Intel) is providing HDCP for HDMI. In addition, HDMI has the support of major motion picture producers Fox, Universal, Warner Bros., and Disney, and system operators DirecTV and EchoStar (Dish Network) as well as CableLabs and Samsung.
Specifications
HDMI defines the protocol and electrical specifications for the signaling, as well as the pin-out, electrical and mechanical requirements of the cable and connectors.
Connectors
The HDMI Specification has expanded to include three connectors, each intended for different markets. The standard Type A HDMI connector has 19 pins, with bandwidth to support all SDTV, EDTV and HDTV modes and more. The plug outside dimensions are 13.9 mm wide by 4.45 mm high. Type A is electrically compatible with single-link DVI-D. A higher resolution version called Type B is defined in HDMI 1.0. Type B has 29 pins (21.2 mm wide), allowing it to carry an expanded video channel for use with very high-resolution future displays, such as WQSXGA (3200x2048). Type B is electrically compatible with dual-link DVI-D, but is not in general use. The Type C mini-connector is intended for portable devices. It is smaller than Type A (10.42 mm by 2.42 mm) but has the same 19-pin configuration.
Cable
The HDMI cable can be used to carry video, audio, and/or device-controlling signals (CEC). Adaptor cables, from Type A to Type C, are available.
Cable length
The HDMI specification does not define a maximum cable length. As with all cables, signal attenuation becomes too high at a certain length. Instead, HDMI specifies a minimum performance standard. Any cable meeting that specification is compliant. Different construction quality and materials will enable cables of different lengths. In addition, higher performance requirements must be met to support video formats with higher resolutions and/or frame rates than the standard HDTV formats. The signal attenuation and intersymbol interference caused by the cables can be compensated by using Adaptive Equalization. HDMI 1.3 defined two categories of cables: Category 1 (standard or HDTV) and Category 2 (high-speed or greater than HDTV) to reduce the confusion about which cables support which video formats. Using 28 AWG, a cable of about 5 metres (~16 ft) can be manufactured easily and inexpensively to Category 1 specifications. Higher-quality construction (24 AWG, tighter construction tolerances, etc.) can reach lengths of 12 to 15 metres (~39 to 49 ft). In addition, active cables (fiber optic or dual Cat-5 cables instead of standard copper) can be used to extend HDMI to 100 metres or more. Some companies also offer amplifiers, equalizers and repeaters that can string several standard (non-active) HDMI cables together.
HDMI and high-definition optical media players
Both introduced in 2006, Blu-ray Disc and HD DVD offer new high-fidelity audio features that require HDMI for best results. Dolby Digital Plus (DD+), Dolby TrueHD and DTS-HD Master Audio use bitrates exceeding TOSLINK's capacity. HDMI 1.3 can transport DD+, TrueHD, and DTS-HD bitstreams in compressed form. This capability would allow a preprocessor or audio/video receiver with the necessary decoder to decode the data itself, but has limited usefulness for HD DVD and Blu-ray. HD DVD and Blu-ray permit "interactive audio", where the disc-content tells the player to mix multiple audio sources together, before final output. Consequently, most players will handle audio-decoding internally, and simply output LPCM audio all the time. Multichannel LPCM can be transported over an HDMI 1.1 (or higher) connection. As long as the audio/video receiver (or preprocessor) supports multi-channel LPCM audio over HDMI, and supports HDCP, the audio reproduction is equal in resolution to HDMI 1.3. However, many of the cheapest AV receivers do not support audio over HDMI and are often labeled as "HDMI passthrough" devices. Note that not all of the features of an HDMI version may be implemented in products adhering to that version since certain features of HDMI, such as Deep Color and xvYCC support, are optional.
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