HDMI
HDMI (High-Definition Multimedia Interface) is a brand of proprietary digital interface used to transmit high-quality video and audio signals between devices. It is commonly used to connect devices such as televisions, computer monitors, projectors, gaming consoles, and personal computers.[2] HDMI supports uncompressed video and either compressed or uncompressed digital audio, allowing a single cable to carry both signals. Introduced in 2003, HDMI largely replaced older analog video standards such as composite video, S-Video, and VGA in consumer electronics. It was developed based on the CEA-861 standard, which was also used with the earlier Digital Visual Interface (DVI). HDMI is electrically compatible with DVI video signals, and adapters allow interoperability between the two without signal conversion or loss of quality. Adapters and active converters are also available for connecting HDMI to other video interfaces, including the older analog formats, as well as digital formats such as DisplayPort. HDMI has gone through multiple revisions since its introduction, with each version adding new features while maintaining backward compatibility. In addition to transmitting audio and video, HDMI also supports data transmission for features such as Consumer Electronics Control (CEC), which allows devices to control each other through a single remote, and the HDMI Ethernet Channel (HEC), which enables network connectivity between compatible devices. It also supports the Display Data Channel (DDC), used for automatic configuration between source devices and displays. Newer versions include advanced capabilities such as 3D video, higher resolutions, expanded color spaces, and the Audio Return Channel (ARC), which allows audio to be sent from a display back to an audio system over the same HDMI cable. Smaller connector types, Mini and Micro HDMI, were also introduced for use with compact devices like camcorders and tablets. As of January 2021,[update] nearly 10 billion HDMI-enabled devices have been sold worldwide, making it one of the most widely adopted audio/video interfaces in consumer electronics. HistoryThe HDMI founders were Hitachi, Matsushita (now Panasonic), Maxell, Philips, Silicon Image (now Lattice Semiconductor), Sony, Thomson (now Vantiva), and Toshiba.[3] Intel contributed the HDCP copy protection system.[4] The new format won the support of motion picture studios Fox, Universal, Warner Bros. and Disney, along with content distributors DirecTV, EchoStar (Dish Network) and CableLabs.[2] The HDMI founders began development on HDMI 1.0 on April 16, 2002, with the goal of creating an AV connector that was backward-compatible with DVI.[5][6] At the time, DVI-HDCP (DVI with HDCP) and DVI-HDTV (DVI-HDCP using the CEA-861-B video standard) were being used on HDTVs.[6][7] HDMI 1.0 was designed to improve on DVI-HDTV by using a smaller connector and adding audio capability, enhanced Y′CBCR capability, and consumer electronics control functions.[6][7] The first Authorized Testing Center (ATC), which tests HDMI products, was opened by Silicon Image on June 23, 2003, in California, United States.[8] The first ATC in Japan was opened by Panasonic on May 1, 2004, in Osaka.[9] The first ATC in Europe was opened by Philips on May 25, 2005, in Caen, France.[10] The first ATC in China was opened by Silicon Image on November 21, 2005, in Shenzhen.[11] The first ATC in India was opened by Philips on June 12, 2008, in Bangalore.[12] The HDMI website contains a list of all the ATCs.[13] According to In-Stat, the number of HDMI devices sold was 5 million in 2004, 17.4 million in 2005, 63 million in 2006, and 143 million in 2007.[14][15][16] HDMI has become the de facto standard for HDTVs, and according to In-Stat, around 90% of digital televisions in 2007 included HDMI.[14][17][18][19][20] In-Stat has estimated that 229 million HDMI devices were sold in 2008.[21] On April 8, 2008, there were over 850 consumer electronics and PC companies that had adopted the HDMI specification (HDMI adopters).[22][23] On January 7, 2009, HDMI Licensing, LLC announced that HDMI had reached an installed base of over 600 million HDMI devices.[23] In-Stat estimated that 394 million HDMI devices would sell in 2009 and that all digital televisions by the end of 2009 would have at least one HDMI input.[23] On January 28, 2008, In-Stat reported that shipments of HDMI were expected to exceed those of DVI in 2008, driven primarily by the consumer electronics market.[14][24] In 2008, PC Magazine awarded a Technical Excellence Award in the Home Theater category for an "innovation that has changed the world" to the CEC portion of the HDMI specification.[25] Ten companies were given a Technology and Engineering Emmy Award for their development of HDMI by the National Academy of Television Arts and Sciences on January 7, 2009.[26] On October 25, 2011, the HDMI Forum was established by the HDMI founders to create an open organization so that interested companies can participate in the development of the HDMI specification.[27][28] All members of the HDMI Forum have equal voting rights, may participate in the Technical Working Group, and if elected can be on the Board of Directors.[28] There is no limit to the number of companies allowed in the HDMI Forum though companies must pay an annual fee of US$15,000 with an additional annual fee of $5,000 for those companies that serve on the Board of Directors.[28] The Board of Directors is made up of 11 companies who are elected every two years by a general vote of HDMI Forum members.[28] All future development of the HDMI specification take place in the HDMI Forum and are built upon the HDMI 1.4b specification.[28] Also on the same day HDMI Licensing, LLC announced that there were over 1,100 HDMI adopters and that over 2 billion HDMI-enabled products had shipped since the launch of the HDMI standard.[29][27] From October 25, 2011, all development of the HDMI specification became the responsibility of the newly created HDMI Forum.[27] On January 8, 2013, HDMI Licensing, LLC announced that there were over 1,300 HDMI adopters and that over 3 billion HDMI devices had shipped since the launch of the HDMI standard.[30][31] The day also marked the 10th anniversary of the release of the first HDMI specification.[30][31] As of January 2021,[update] nearly 10 billion HDMI devices had been sold.[32] SpecificationsThe HDMI specification defines the protocols, signals, electrical interfaces and mechanical requirements of the standard.[33]: p. V The maximum pixel clock rate for HDMI 1.0 is 165 MHz, which is sufficient to allow 1080p and WUXGA (1920×1200) at 60 Hz. HDMI 1.3 increases that to 340 MHz, which allows for higher resolution (such as WQXGA, 2560×1600) across a single digital link.[34] An HDMI connection can either be single-link (type A/C/D) or dual-link (type B) and can have a video pixel rate of 25 MHz to 340 MHz (for a single-link connection) or 25 MHz to 680 MHz (for a dual-link connection). Video formats with pixel rates below 25 MHz (like 480i at 13.5 MHz) are transmitted over TMDS links using a pixel-repetition scheme.[33]: §§3, 6.4 Audio/videoHDMI uses the Consumer Technology Association/Electronic Industries Alliance 861 standards. HDMI 1.0 to HDMI 1.2a uses the EIA/CEA-861-B video standard, HDMI 1.3 uses the CEA-861-D video standard, and HDMI 1.4 uses the CEA-861-E video standard.[33]: III The CEA-861-E document defines "video formats and waveforms; colorimetry and quantization; transport of compressed and uncompressed LPCM audio; carriage of auxiliary data; and implementations of the Video Electronics Standards Association (VESA) Enhanced Extended Display Identification Data Standard (E-EDID)".[35] On July 15, 2013, the CEA announced the publication of CEA-861-F, a standard that can be used by video interfaces such as DVI, HDMI, and LVDS.[36] CEA-861-F adds the ability to transmit several Ultra HD video formats and additional color spaces.[36] To ensure baseline compatibility between different HDMI sources and displays (as well as backward compatibility with the electrically compatible DVI standard) all HDMI devices must implement the sRGB color space at 8 bits per component.[33]: §6.2.3 Ability to use the Y′CBCR color space and higher color depths ("deep color") is optional. HDMI permits sRGB 4:4:4 chroma subsampling (8–16 bits per component), xvYCC 4:4:4 chroma subsampling (8–16 bits per component), Y′CBCR 4:4:4 chroma subsampling (8–16 bits per component), or Y′CBCR 4:2:2 chroma subsampling (8–12 bits per component). The color spaces that can be used by HDMI are ITU-R BT.601, ITU-R BT.709-5 and IEC 61966-2-4.[33]: §§6.5,6.7.2 For digital audio, if an HDMI device has audio, it is required to implement the baseline format: stereo (uncompressed) PCM. Other formats are optional, with HDMI allowing up to 8 channels of uncompressed audio at sample sizes of 16 bits, 20 bits, or 24 bits, with sample rates of 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, or 192 kHz.[33]: §7 HDMI also carries any IEC 61937-compliant compressed audio stream, such as Dolby Digital and DTS, and up to 8 channels of one-bit DSD audio (used on Super Audio CDs) at rates up to four times that of Super Audio CD.[33]: §7 With version 1.3, HDMI allows lossless compressed audio streams Dolby TrueHD and DTS-HD Master Audio.[33]: §7 As with the Y′CBCR video, audio capability is optional. Audio return channel (ARC) is a feature introduced in the HDMI 1.4 standard.[37] "Return" refers to the case where the audio comes from the TV and can be sent "upstream" to the AV receiver using the HDMI cable connected to the AV receiver.[37] An example given on the HDMI website is that a TV that directly receives a terrestrial/satellite broadcast, or has a video source built in, sends the audio "upstream" to the AV receiver.[37] The HDMI standard was not designed to pass closed caption data (for example, subtitles) to the television for decoding.[38] As such, any closed caption stream must be decoded and included as an image in the video stream(s) prior to transmission over an HDMI cable to appear on the DTV. This limits the caption style (even for digital captions) to only that decoded at the source prior to HDMI transmission. This also prevents closed captions when transmission over HDMI is required for upconversion. For example, a DVD player that sends an upscaled 720p/1080i format via HDMI to an HDTV has no way to pass Closed Captioning data so that the HDTV can decode it, as there is no line 21 VBI in that format. Communication channels
HDMI has three physically separate communication channels, which are the VESA DDC, TMDS and the optional CEC.[33]: §8.1 HDMI 1.4 added ARC and HEC.[37][39] Display Data Channel (DDC)The Display Data Channel (DDC) is a VESA standard communications channel based on the I2C bus specification. HDMI specifically requires the device implement the Enhanced Display Data Channel (E-DDC), which is used by the HDMI source device to read the E-EDID data from the HDMI sink device to learn what audio/video formats it can take.[33]: §§8.1, CEC-1.2–CEC-1.3 HDMI requires that the E-DDC implement I2C standard mode speed (100 kbit/s) and allows it to optionally implement fast mode speed (400 kbit/s).[33]: §4.2.8 I2C address 0x74 on the DDC channel is actively used for High-bandwidth Digital Content Protection (HDCP). Transition-minimized differential signaling (TMDS)Transition-minimized differential signaling (TMDS) on HDMI interleaves video, audio and auxiliary data using three different packet types, called the video data period, the data island period and the control period. During the video data period, the pixels of an active video line are transmitted. During the data island period (which occurs during the horizontal and vertical blanking intervals), audio and auxiliary data are transmitted within a series of packets. The control period occurs between video and data island periods.[33]: §5.1.2 Both HDMI and DVI use TMDS to send 10-bit characters that are encoded using 8b/10b encoding that differs from the original IBM form for the video data period and 2b/10b encoding for the control period. HDMI adds the ability to send audio and auxiliary data using 4b/10b encoding for the data island period. Each data island period is 32 pixels in size and contains a 32-bit packet header, which includes 8 bits of BCH ECC parity data for error correction and describes the contents of the packet. Each packet contains four subpackets, and each subpacket is 64 bits in size, including 8 bits of BCH ECC parity data, allowing for each packet to carry up to 224 bits of audio data. Each data island period can contain up to 18 packets. Seven of the 15 packet types described in the HDMI 1.3a specifications deal with audio data, while the other 8 types deal with auxiliary data. Among these are the general control packet and the gamut metadata packet. The general control packet carries information on AVMUTE (which mutes the audio during changes that may cause audio noise) and color depth (which sends the bit depth of the current video stream and is required for deep color). The gamut metadata packet carries information on the color space being used for the current video stream and is required for xvYCC.[33]: §§5.2–5.3,6.5.3,6.7.2,6.7.3 Consumer Electronics Control (CEC)Consumer Electronics Control (CEC) is an HDMI feature designed to allow the user to command and control up to 15 CEC-enabled devices, that are connected through HDMI,[40][41] by using only one of their remote controls (for example by controlling a television set, set-top box, and DVD player using only the remote control of the TV). CEC also allows for individual CEC-enabled devices to command and control each other without user intervention.[33]: §CEC-3.1 It is a one-wire bidirectional serial bus that is based on the CENELEC standard AV.link protocol to perform remote control functions.[42] CEC wiring is mandatory, although implementation of CEC in a product is optional.[33]: §8.1 It was defined in HDMI Specification 1.0 and updated in HDMI 1.2, HDMI 1.2a and HDMI 1.3a (which added timer and audio commands to the bus).[33]: §§CEC-1.2, CEC-1.3, CEC-3.1, CEC-5 USB to CEC adapters exist that allow a computer to control CEC-enabled devices.[43][44][45][46] HDMI Ethernet and Audio Return ChannelIntroduced in HDMI 1.4, HDMI Ethernet and Audio Return Channel (HEAC) adds a high-speed bidirectional data communication link (HEC) and the ability to send audio data upstream to the source device (ARC). HEAC utilizes two lines from the connector: the previously unused Reserved pin (called HEAC+) and the Hot Plug Detect pin (called HEAC−).[47]: §HEAC-2.1 If only ARC transmission is required, a single mode signal using the HEAC+ line can be used, otherwise, HEC is transmitted as a differential signal over the pair of lines, and ARC as a common mode component of the pair.[47]: §HEAC-2.2 Audio Return Channel (ARC) and Enhanced Audio Return Channel (eARC)ARC (Audio Return Channel) is an audio link introduced in 2009 with the HDMI 1.4 standard meant to replace other cables between the TV and the A/V receiver or speaker system.[37] This direction is used when the TV is the one that generates or receives the video stream instead of the other equipment.[37] A typical case is the running of an app on a smart TV such as Netflix, but reproduction of audio is handled by the other equipment.[37] Without ARC, the audio output from the TV must be routed by another cable, typically TOSLink or RCA, into the speaker system.[48] ARC supports stereo PCM and compressed codecs Dolby Digital, Dolby Digital Plus and DTS up to 5.1 channels, with Dolby Atmos metadata in Dolby codecs.[49] eARC (Enhanced Audio Return Channel) was introduced in 2017 with the HDMI 2.1 standard. eARC has higher bandwidth (37 Mbps) and adds support for uncompressed surround sound, Dolby TrueHD and DTS-HD Master Audio passthrough with support for up to 32 channels. eARC requires an "Ultra High Speed", "Premium High Speed with Ethernet", or "High Speed with Ethernet" HDMI cable.[50][51] HDMI Ethernet Channel (HEC)HDMI Ethernet Channel technology consolidates video, audio, and data streams into a single HDMI cable, and the HEC feature enables IP-based applications over HDMI and provides a bidirectional Ethernet communication at 100 Mbit/s.[39] The physical layer of the Ethernet implementation uses a hybrid to simultaneously send and receive attenuated 100BASE-TX-type signals through a single twisted pair.[52][53] Compatibility with DVI  HDMI is backward compatible with single-link Digital Visual Interface digital video (DVI-D or DVI-I, but not DVI-A or dual-link DVI). No signal conversion is required when an adapter or asymmetric cable is used, so there is no loss of video quality.[33]: appx. C From a user's perspective, an HDMI display can be driven by a single-link DVI-D source, since HDMI and DVI-D define an overlapping minimum set of allowed resolutions and frame-buffer formats to ensure a basic level of interoperability. In the reverse case, a DVI-D monitor has the same level of basic interoperability unless content protection with High-bandwidth Digital Content Protection (HDCP) interferes—or the HDMI color encoding is in component color space Y′CBCR instead of RGB, which is not possible in DVI. An HDMI source, such as a Blu-ray player, may require an HDCP-compliant display, and refuse to output HDCP-protected content to a non-compliant display.[54] A further complication is that there is a small amount of display equipment, such as some high-end home theater projectors, designed with HDMI inputs but not HDCP-compliant. Any DVI-to-HDMI adapter can function as an HDMI-to-DVI adapter (and vice versa).[55] Typically, the only limitation is the gender of the adapter's connectors and the gender of the cables and sockets it is used with. Features specific to HDMI, such as remote-control and audio transport, are not available in devices that use legacy DVI-D signalling. However, many devices output HDMI over a DVI connector (e.g., ATI 3000-series and NVIDIA GTX 200-series video cards),[33]: appx. C [56] and some multimedia displays may accept HDMI (including audio) over a DVI input. Exact capabilities beyond basic compatibility vary. Adapters are generally bi-directional. Content protection (HDCP)High-bandwidth Digital Content Protection (HDCP) is a newer form of digital rights management (DRM). Intel created the original technology to make sure that digital content followed the guidelines set by the Digital Content Protection group. HDMI can use HDCP to encrypt the signal if required by the source device. Content Scramble System (CSS), Content Protection for Recordable Media (CPRM) and Advanced Access Content System (AACS) require the use of HDCP on HDMI when playing back encrypted DVD Video, DVD Audio, HD DVD and Blu-ray Discs. The HDCP repeater bit controls the authentication and switching/distribution of an HDMI signal. According to HDCP Specification 1.2 (beginning with HDMI CTS 1.3a), any system that implements HDCP must do so in a fully compliant manner. HDCP testing that was previously only a requirement for optional tests such as the "Simplay HD" testing program is now part of the requirements for HDMI compliance.[33]: §9.2 [57][58] HDCP accommodates up to 127 connected devices with up to 7 levels, using a combination of sources, sinks and repeaters.[59] A simple example of this is several HDMI devices connected to an HDMI AV receiver that is connected to an HDMI display.[59] Devices called HDCP strippers can remove the HDCP information from the video signal so the video can play on non-HDCP-compliant displays,[60] though a fair use and non-disclosure form must usually be signed with a registering agency before use. Connectors   There are five HDMI connector types. Type A/B are defined in the HDMI 1.0 specification, type C is defined in the HDMI 1.3 specification, and type D/E are defined in the HDMI 1.4 specification.
The HDMI alternate mode lets a user connect the reversible USB-C connector with the HDMI source devices (mobile, tablet, laptop). This cable connects to video display/sink devices using any of the native HDMI connectors. This is an HDMI cable, in this case a USB-C to HDMI cable.[68] Cables  An HDMI cable is composed of four shielded twisted pairs, with a characteristic impedance of 100 Ω (±15%), plus seven separate conductors. HDMI cables with Ethernet differ in that three of the separate conductors instead form an additional shielded twisted pair (with the CEC/DDC ground as a shield).[47]: §HEAC-2.9 Although no maximum length for an HDMI cable is specified, signal attenuation (dependent on the cable's construction quality and conducting materials) limits usable lengths in practice[69][70] and certification is difficult to achieve for lengths beyond 13 m.[71] HDMI 1.3 defines two cable categories: Category 1-certified cables, which have been tested at 74.25 MHz (which would include resolutions such as 720p60 and 1080i60), and Category 2-certified cables, which have been tested at 340 MHz (which would include resolutions such as 1080p60 and 4K30).[33]: §4.2.6 [62][72] Category 1 HDMI cables are marketed as "Standard" and Category 2 HDMI cables as "High Speed".[2] This labeling guideline for HDMI cables went into effect on October 17, 2008.[73][74] Category 1 and 2 cables can either meet the required parameter specifications for inter-pair skew, far-end crosstalk, attenuation and differential impedance, or they can meet the required non-equalized/equalized eye diagram requirements.[33]: §4.2.6 A cable of about 5 meters (16 feet) can be manufactured to Category 1 specifications easily and inexpensively by using 28 AWG (0.081 mm2) conductors.[69] With better quality construction and materials, including 24 AWG (0.205 mm2) conductors, an HDMI cable can reach lengths of up to 15 meters (49 feet).[69] Many HDMI cables under 5 meters in length that were made before the HDMI 1.3 specification can work as Category 2 cables, but only Category 2-tested cables are guaranteed to work for Category 2 purposes.[75] HDMI cables are certified to guarantee a certain level of performance at an Authorized Testing Center (ATC). As of the HDMI 2.2 specification, the following certifications are defined for HDMI cables in consumer applications:[76]
Separate certifications also exist for "automotive" Standard and High Speed HDMI cables, which use a different connector with a latching mechanism. ExtendersAn HDMI extender is a single device (or pair of devices) powered with an external power source or with the 5 V DC from the HDMI source.[77][78][79] Long cables can cause instability of HDCP and blinking on the screen due to the weakened DDC signal that HDCP requires.[citation needed] HDCP DDC signals must be multiplexed with TMDS video signals to comply with HDCP requirements for HDMI extenders based on a single Category 5/Category 6 cable.[80][81] Several companies offer amplifiers, equalizers, and repeaters that can string several standard HDMI cables together. Active HDMI cables use electronics within the cable to boost the signal and allow for HDMI cables of up to 30 meters (98 feet).[77] Those based on HDBaseT can extend to 100 meters. HDMI extenders that are based on dual Category 5/Category 6 cable can extend HDMI to 250 meters (820 feet) while HDMI extenders based on optical fiber can extend HDMI to 300 meters (980 feet).[78][79] LicensingThe HDMI specification is not an open standard; manufacturers need to be licensed by HDMI LA in order to implement HDMI in any product or component. Companies that are licensed by HDMI LA are known as HDMI Adopters.[82] HDMI adoptersWhile earlier versions of HDMI specs are available to the public for download, only adopters have access to the latest standards (HDMI 1.4b/2.1). Only adopters have access to the compliance test specification (CTS) that is used for compliance and certification. Compliance testing is required before any HDMI product can be legally sold.
HDMI fee structureThere are two annual fee structures associated with being an HDMI adopter:
The annual fee is due upon the execution of the Adopter Agreement, and must be paid on the anniversary of this date each year thereafter. The royalty fee structure is the same for all volumes. The following variable per-unit royalty is device-based and not dependent on number of ports, chips or connectors:
Use of HDMI logo requires compliance testing. Adopters need to license HDCP separately. The HDMI royalty is only payable on licensed products that will be sold on a stand-alone basis (i.e., that are not incorporated into another licensed product that is subject to an HDMI royalty). For example, if a cable or IC is sold to an adopter who then includes it in a television subject to a royalty, then the cable or IC maker would not pay a royalty, and the television manufacturer would pay the royalty on the final product. If the cable is sold directly to consumers, then the cable would be subject to a royalty.[83] Versions HDMI devices and cables are designed based on the HDMI Specification, a document published by HDMI Licensing (through version 1.4b) or the HDMI Forum (from version 2.0 onward). The HDMI Specification defines the minimum baseline requirements that all HDMI devices must adhere to for interoperability, as well as a large set of optional features that HDMI devices may support. The specification is periodically updated to add clarifications or define new capabilities that HDMI devices may implement. Each new version of the specification expands the list of possible features, but does not mandate support for new features in all devices or establish any "classes" of HDMI products which must support certain capabilities. Version numbers do not refer to classes or tiers of products with certain levels of feature support, and as such, HDMI specification "version numbers" are not a method of describing support for specific features or describing the capabilities of an HDMI device or cable.[84][85][86] In 2009, HDMI Licensing banned the use of "version numbers" in labeling HDMI products.[87] Instead, HDMI devices should explicitly declare which features and capabilities they support. For HDMI cables, a speed rating system was established since feature support is not dependent on the cable (apart from inline Ethernet and ARC); the cable only affects the maximum possible speed of the connection.[85] HDMI cables should be labeled with the appropriate speed certification (i.e. Standard Speed, High Speed, or Ultra High Speed), not a "version number".[84] Version 1.0HDMI 1.0 was released on December 9, 2002, and is a single-cable digital audio/video connector interface. The link architecture is based on DVI, using exactly the same video transmission format but sending audio and other auxiliary data during the blanking intervals of the video stream. HDMI 1.0 allows a maximum TMDS clock of 165 MHz (4.95 Gbit/s bandwidth per link), the same as DVI. It defines two connectors called type A and type B, with pinouts based on the Single-Link DVI-D and Dual-Link DVI-D connectors respectively, though the type B connector was never used in any commercial products. HDMI 1.0 uses TMDS encoding for video transmission, giving it 3.96 Gbit/s of video bandwidth (1920 × 1080 or 1920 × 1200 at 60 Hz) and 8-channel LPCM/192 kHz/24-bit audio. HDMI 1.0 requires support for RGB video, with optional support for Y′CBCR 4:4:4 and 4:2:2 (mandatory if the device has support for Y′CBCR on other interfaces). Color depth of 10 bpc (30 bit/px) or 12 bpc (36 bit/px) is allowed when using 4:2:2 subsampling, but only 8 bpc (24 bit/px) color depth is permitted when using RGB or Y′CBCR 4:4:4. Only the Rec. 601 and Rec. 709 color spaces are supported. HDMI 1.0 allows only specific pre-defined video formats, including all the formats defined in EIA/CEA-861-B and some additional formats listed in the HDMI Specification itself. All HDMI sources/sinks must also be capable of sending/receiving native Single-Link DVI video and be fully compliant with the DVI Specification.[88] Version 1.1HDMI 1.1 was released on May 20, 2004, and added support for DVD-Audio. Version 1.2HDMI 1.2 was released on August 8, 2005, and added the option of One Bit Audio, used on Super Audio CDs, at up to 8 channels. To make HDMI more suitable for use on PC devices, version 1.2 also removed the requirement that only explicitly supported formats be used. It added the ability for manufacturers to create vendor-specific formats, allowing any arbitrary resolution and refresh rate rather than being limited to a pre-defined list of supported formats. In addition, it added explicit support for several new formats including 720p at 100 and 120 Hz and relaxed the pixel format support requirements so that sources with only native RGB output (PC sources) would not be required to support Y′CBCR output.[89]: §6.2.3 HDMI 1.2a was released on December 14, 2005 and fully specifies Consumer Electronic Control (CEC) features, command sets and CEC compliance tests.[89] Version 1.3HDMI 1.3 was released on June 22, 2006, and increased the maximum TMDS clock to 340 MHz (10.2 Gbit/s).[33][34][90] Like previous versions, it uses TMDS encoding, giving it a maximum video bandwidth of 8.16 Gbit/s (sufficient for 1920 × 1080 at 144 Hz or 2560 × 1440 at 75 Hz). It added support for 10 bpc, 12 bpc, and 16 bpc color depth (30, 36, and 48 bit/px), called deep color. It also added support for the xvYCC color space, in addition to the ITU-R BT.601 and BT.709 color spaces supported by previous versions, and added the ability to carry metadata defining color gamut boundaries. It also optionally allows output of Dolby TrueHD and DTS-HD Master Audio streams for external decoding by AV receivers.[91] It incorporates automatic audio syncing (audio video sync) capability.[34] It defined cable Categories 1 and 2, with Category 1 cable being tested up to 74.25 MHz and Category 2 being tested up to 340 MHz.[33]: §4.2.6 It also added the new HDMI type C "Mini" connector for portable devices.[33]: §4.1.1 [92] HDMI 1.3a was released on November 10, 2006, and had cable and sink modifications for HDMI type C, source termination recommendations, and removed undershoot and maximum rise/fall time limits. It also changed CEC capacitance limits, and CEC commands for timer control were brought back in an altered form, with audio control commands added. It also added the optional ability to stream SACD in its bitstream DST format rather than uncompressed raw DSD.[33] HDMI 1.3a is available to download free of charge, after registration.[93] Version 1.4 HDMI 1.4 was released on June 5, 2009, and first came to market after Q2 of 2009.[62][94][95] Retaining the bandwidth of the previous version, HDMI 1.4 defined standardized timings to use for 4096 × 2160 at 24 Hz, 3840 × 2160 at 24, 25, and 30 Hz, and added explicit support for 1920 × 1080 at 120 Hz with CTA-861 timings.[64]: §6.3.2 It also added an HDMI Ethernet Channel (HEC) that accommodates a 100 Mbit/s Ethernet connection between the two HDMI connected devices so they can share an Internet connection,[39] introduced an audio return channel (ARC),[37] 3D Over HDMI, a new Micro HDMI Connector, an expanded set of color spaces with the addition of sYCC601, Adobe RGB and Adobe YCC601, and an Automotive Connection System.[62][96][97][98][99] HDMI 1.4 defined several stereoscopic 3D formats including field alternative (interlaced), frame packing (a full resolution top-bottom format), line alternative full, side-by-side half, side-by-side full, 2D + depth, and 2D + depth + graphics + graphics depth (WOWvx).[61][100][101] HDMI 1.4 requires that 3D displays implement the frame packing 3D format at either 720p50 and 1080p24 or 720p60 and 1080p24.[101] High Speed HDMI cables as defined in HDMI 1.3 work with all HDMI 1.4 features except for the HDMI Ethernet Channel, which requires the new High Speed HDMI Cable with Ethernet defined in HDMI 1.4.[61][100][101] HDMI 1.4a was released on March 4, 2010, and added two mandatory 3D formats for broadcast content, which was deferred with HDMI 1.4 pending the direction of the 3D broadcast market.[102][103] HDMI 1.4a has defined mandatory 3D formats for broadcast, game, and movie content.[102] HDMI 1.4a requires that 3D displays implement the frame packing 3D format at either 720p50 and 1080p24 or 720p60 and 1080p24, side-by-side horizontal at either 1080i50 or 1080i60, and top-and-bottom at either 720p50 and 1080p24 or 720p60 and 1080p24.[103] HDMI 1.4b was released on October 11, 2011,[104] containing only minor clarifications to the 1.4a document. HDMI 1.4b is the last version of the standard that HDMI LA is responsible for. All later versions of the HDMI Specification are produced by the HDMI Forum, created on October 25, 2011.[27][105] Version 2.0HDMI 2.0, referred to by some manufacturers as HDMI UHD, was released on September 4, 2013.[106] HDMI 2.0 increases the maximum bandwidth to 18.0 Gbit/s.[106][107][108] HDMI 2.0 uses TMDS encoding for video transmission like previous versions, giving it a maximum video bandwidth of 14.4 Gbit/s. This enables HDMI 2.0 to carry 4K video at 60 Hz with 24 bit/px color depth.[106][109][110] Other features of HDMI 2.0 include support for the Rec. 2020 color space, up to 32 audio channels, up to 1536 kHz audio sample frequency, dual video streams to multiple users on the same screen, up to four audio streams, 4:2:0 chroma subsampling, 25 fps 3D formats, support for the 21:9 aspect ratio, dynamic synchronization of video and audio streams, the HE-AAC and DRA audio standards, improved 3D capability, and additional CEC functions.[106][111][112] HDMI 2.0a was released on April 8, 2015, and added support for High Dynamic Range (HDR) video with static metadata.[113] HDMI 2.0b was released March 2016.[114] HDMI 2.0b initially supported the same HDR10 standard as HDMI 2.0a as specified in the CTA-861.3 specification.[111] In December 2016 additional support for HDR Video transport was added to HDMI 2.0b in the CTA-861-G specification, which extends the static metadata signaling to include hybrid log–gamma (HLG).[111][115][116] Version 2.1HDMI 2.1 was officially announced by the HDMI Forum on January 4, 2017,[117][118] and was released on November 28, 2017.[119] It adds support for higher resolutions and higher refresh rates, including 4K 120 Hz and 8K 60 Hz. HDMI 2.1 also introduces a new HDMI cable category called Ultra High Speed (referred to as 48G during development), which certifies cables at the new higher speeds that these formats require. Ultra High Speed HDMI cables are backwards compatible with older HDMI devices, and older cables are compatible with new HDMI 2.1 devices, though the full 48 Gbit/s bandwidth is only supported with the new cables. Some systems may not be able to use HDMI 2.1 because the HDMI Forum is preventing its use in open source implementations (such as Linux open source drivers). Users of those systems may need to use DisplayPort instead to access high resolutions and speeds.[120] The following features were added to the HDMI 2.1 Specification:[119][121]
Video formats that require more bandwidth than 18.0 Gbit/s (4K 60 Hz 8 bpc RGB), such as 4K 60 Hz 10 bpc (HDR), 4K 120 Hz, and 8K 60 Hz, may require the new "Ultra High Speed" or "Ultra High Speed with Ethernet" cables.[118] HDMI 2.1's other new features are supported with existing HDMI cables. The increase in maximum bandwidth is achieved by increasing both the bitrate of the data channels and the number of channels. Previous HDMI versions use three data channels (each operating at up to 6.0 Gbit/s in HDMI 2.0, or up to 3.4 Gbit/s in HDMI 1.4), with an additional channel for the TMDS clock signal, which runs at a fraction of the data channel speed (one tenth the speed, or up to 340 MHz, for signaling rates up to 3.4 Gbit/s; one fortieth the speed, or up to 150 MHz, for signaling rates between 3.4 and 6.0 Gbit/s). HDMI 2.1 doubles the signaling rate of the data channels to 12 Gbit/s. The structure of the data has been changed to use a new packet-based format with an embedded clock signal, which allows what was formerly the TMDS clock channel to be used as a fourth data channel instead, increasing the signaling rate across that channel to 12 Gbit/s as well. These changes increase the aggregate bandwidth from 18.0 Gbit/s (3 × 6.0 Gbit/s) to 48.0 Gbit/s (4 × 12.0 Gbit/s), a 2.66× improvement in bandwidth. In addition, the data is transmitted more efficiently by using a 16b/18b encoding scheme, which uses a larger percentage of the bandwidth for data rather than DC balancing compared to the TMDS scheme used by previous versions (88.8% compared to 80%). This, in combination with the 2.66× bandwidth, raises the maximum data rate of HDMI 2.1 from 14.4 Gbit/s to 42.6 Gbit/s. Subtracting overhead for FEC, the usable data rate is approximately 42.0 Gbit/s, around 2.92× the data rate of HDMI 2.0.[123][124] The 48 Gbit/s bandwidth provided by HDMI 2.1 is enough for 8K resolution at approximately 50 Hz, with 8 bpc RGB or Y′CBCR 4:4:4 color. To achieve even higher formats, HDMI 2.1 can use Display Stream Compression (DSC) with a compression ratio of up to 3∶1. Using DSC, formats up to 8K (7680 × 4320) 120 Hz or 10K (10240 × 4320) 100 Hz at 8 bpc RGB/4:4:4 are possible. Using Y′CBCR with 4:2:2 or 4:2:0 chroma subsampling in combination with DSC can allow for even higher formats.[121] HDMI 2.1a was released on February 15, 2022, and added support for Source-Based Tone Mapping (SBTM).[125][126] HDMI 2.1b was released on August 10, 2023.[127] Version 2.2HDMI 2.2 was announced on January 6, 2025, it was released on June 25, 2025.[128] The maximum allowed bit rate is increased to 96 Gbit/s and Latency Indication Protocol (LIP) support is added for improving audio and video synchronization.[129] Version comparisonMain specifications
Refresh frequency limits for common resolutionsThe maximum limits for TMDS transmission are calculated using standard data rate calculations.[144] For FRL transmission, the limits are calculated using the capacity computation algorithm provided by the HDMI Specification.[145]: §6.5.6.2.1 All calculations assume uncompressed RGB video with CVT-RB v2 timing. Maximum limits may differ if compression (i.e. DSC) or Y′CBCR 4:2:0 chroma subsampling are used. Display manufacturers may also use non-standard blanking intervals (a Vendor-Specific Timing Format as defined in the HDMI Specification[33]: §6.1 ) rather than CVT-RB v2 to achieve even higher frequencies when bandwidth is a constraint. The refresh frequencies in the below table do not represent the absolute maximum limit of each interface, but rather an estimate based on a modern standardized timing formula. The minimum blanking intervals (and therefore the exact maximum frequency that can be achieved) will depend on the display and how many secondary data packets it requires, and therefore will differ from model to model.
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