HDMI interface and protocol

Source: Internet
Author: User

Deep understanding of the HDMI interface
OneHdmiHow the interface works
This diagram is the architecture of the HDMI interface. From the signal source on the left, you can see that the source of the HDMI interface can be any HDMI-enabled device, and the access port can be any device with an HDMI input interface. Whether they are audio devices, video devices, or control devices, the HDMI interface can be used.
The data signal in the HDMI interface is based on the TMDS minimized transmission differential signaling protocol. This data transmission protocol has been widely used in DVI interface. The data signal on the HDMI interface also follows this protocol. This protocol converts standard 8bit data to 10bit signals and uses differential transfer during the conversion process. The technology of differential transmission has also been widely used in the data transmission of Gigabit Ethernet.

Three TMDS data can be used in the transmission of audio and video data in the HDMI interfaceChannel. The video information is converted to the city's continuous 24bit pixel data at the time of transmission, and each clock cycle transmits 10bit of data. The pixel clock cycle transfer ratio is approximately 25MHz to 165MHz. In general, the standard NTSC 480i interlaced signal has a pixel clock transfer ratio of approximately 13.5MHz. If the ratio of the transmission signal is less than 25MHZ,HDMI will use automatic cycle technology to fill the code rate, the signal rate to increase to 25MHz level. While the HDMI interface can transmit up to 165M of data per second, this data throughput capability is quite astonishing. In the next period of time enough to cope with high bitrate, high data flow signal transmission tasks of household appliances.
HDTV the highest standard is 1080p, it's resolution is 1920x1080 per screen, if the transmission of 60 frames per second ([email protected]), then the final pixel clock transmission ratio of 124.4MHz. It seems that the HDMI interface is fully capable of handling today's consumer electronics applications. Of course HDMI also supports dual-interface parallel mode, which can provide an astonishing 330MHz transfer ratio. However, the current dual-parallel HDMI interface will not be used for the general consumer class.
The video signals used in HDMI are encoded in RGB format, such as YCbCr 4:4:4 or YCBCR 4:2:2 format, each of which is 24bit. YCbCr is a digital video signal format that is similar to the YPBPR format. (the current DVD player's component output is the use of YCBCR/YPBPR format) This video signal standard is what we often call "Yuy". Y means brightness, which does not contain information about the color of the image. It is only responsible for recording black and white information in the image.    CB is the difference between blue and luminance in the image (B-y), and CR is the difference between red and brightness (r-y). Then the three values of Y, Cb, CR define the sampling rate when the video is encoded. The "4" above represents the sample rate at NTSC or PAL mode, which is 13.5MHz. Then we see the 4:4:4, meaning that y, Cb, CR encoding sampling rate are 13.5MHz. And we see the 4:2:2 format of CB, CR sampling rate is 6.75MHz. Now you can clearly distinguish which video quality is better in the two YCBCR formats above.
In the HDMI interface, the audio signal can use 2 to 8 channels, with a sample rate of 192KHz per channel. In addition, the HDMI interface provides a DDC display data channel, which sends configuration information and data format information to the video receiving device. The receiving device can read these E-edid enhanced extensions to display the information that identifies the data. Finally, the HDMI interface also provides the CEC consumer electronic control channel, which can control the work of audiovisual equipment.

Second, HDMI interface connector
Depending on the electrical structure and physical shape, the HDMI interface can be divided into types A, type B, type C three kinds. Each type of interface consists of a plug for the socket and wire end for the device end, using a 5V lowVoltageDrive, the impedance is 100 ohms. These three types of plugs provide a reliable TMDS connection.
Type A-type interface

The type A is the standard 19-pin HDMI interface with the highest penetration.
A-type receptacle is a flat "D" type with a narrow upper and lower width. The outer side of the interface is provided with a metal shielding layer of 0.5 mm thick to prevent various interfering signals from the outside. Which is used for the device end of the socket diameter of the widest place 14 mm, 4.55 mm high. 19 The heel pin is arranged in two layers in the center position. The width of each pin is 0.45 mm and the length is 4.1 mm. The type a plug OD is at the widest 13.9 mm and 4.45 mm high. The internal pins are arranged in a ring-shaped arrangement. The HDMI standard specifies that the error of these dimensions should be controlled in a relatively small range (around 0.05 mm) to ensure good contact.
A-type interface can transmit 165MHz of pixel information per clock cycle.
Type B-Type interface

The physical structure of the B-type interface, compared to the A-type interface, the basic shape does not change much, are "D" type. But the maximum width of the socket is 21.3 mm, which is a whole lot bigger than the 14 mm type A. There are 29 pins that can provide dual TMDS transmission channels, thus supporting higher data rates and Dual-link DVI connections.
The B-type interface transmits up to 330MHz of pixel information per clock cycle.
Type C-type interface

The C-Type HDMI interface is designed for compact portable devices, so the C-type receptacle is only 10.5x2.5 mm in size and the plug is only 10.42x2.4 mm. It's very small.
The C-type interface can transmit 165MHz of pixel information per clock cycle.

As indicated in the TMDS standard, the length of the cable must not exceed 15 meters. As a result, the HDMI interface cable length using the TMDS standard is limited to within 15 meters. This length is sufficient for general home and Office applications.
A signal transmitter with a-type HDMI interface can be connected to a receiving device using a B-type interface, at which point a B-to-a conversion interface can be connected smoothly. However, it is important to note that a signal transmitter with a Type B interface is not possible to connect a signal receiving device with a Class A interface. The HDMI interface is now available downCompatible with DVI interfaces, they can be converted to each other using only dedicated cable connections.

Patent license Fee
Unfortunately, the HDMI interface is not an open standard. Manufacturers must pay royalties to the HDMI Standard Development Association in exchange for a production license. But this royalties is not cheap, pay 1 a yearThe $5000 license fee, and the darker one, is a $0.15 license fee for each HDMI interface that is produced. Only in this way can the manufacturer identify the HDMI-enabled logo in its own product and user manual. If the manufacturer is already a member of the HDCP HD Digital Content Protection protocol, then each product with an HDMI interface requires a license fee of $0.04. If manufacturers use HDCP HD Digital content protection in their products, they will have to pay an annual fee of $15000, plus a purchase key fee of $0.005 per product.

Three, pin definition
In order to facilitate access to information, as well as you DIY players on the HDMI interface for further understanding of the type a HDMI interface as an example of the definition of each pin.

1. Data channel (TMDS channel)
Both the HDMI data channel and the DVI data channel use the TMDS signal (minimizing the transmission differential signal). Transmit audio, video, and various ancillary data via TMDS signals.
Signal encoding method: Follow the DVI 1.0 specification. The A-type HDMI interface is single-link, and the B-Type HDMI interface is dual-link (bandwidth increases by one times).
Video pixel bandwidth: from 1.3 MHz to 340 MHz (Type A, HDMI) or to 680 MHz (Type B). Video signals with a bandwidth of less than 25MHz, such as NTSC 480i, will be output in a multiplier fashion. The allowable amount of data per pixel is from 24 bits to 48 bits. Supports 120 images per second, 1080p resolution screen transfer and WQSXGA resolution.
Pixel encoding method: RGB 4:4:4,ycbcr 4:4:4 (8-16 bits per component), YCbCr 4:2:2 (bits per component).
Audio sample rate: Up to khz, 44.1 khz,-khz, 88.2 khz,-khz, 176.4 khz, 192 khz.
Number of audio channels: 8 channels Max.
Audio Stream Specifications: IEC61937 compatible streams, including high-flow lossless signals such as Dolby TrueHD, Dts-hd Master audio.
2.CEC channels (lines must be reserved but not implemented)
The full-text of CEC is consumer Electronics Control, used to transmit industrial specifications of AV Link protocol signals in order to support a single remote control operation of multiple AV machines. is a single-wire bidirectional serial bus.
3.DDC Channel
The DDC is the full text of the display Data channel, and the transmitting and receiving terminals can use the DDC channel to learn about each other's transmission and reception capabilities, but HDMI only needs to know the receiving end (Monitor) capabilities. Use 100kHz clockFrequency of the i²c signal. Transfer data structure to VESA enhanced EDID (V1.3).
3. SCL and SDA
The full text of the SCL is serial CLOCK,SDA's full text is serial Data.
The two feet are used to communicate source (DVD) and display (TV), there is a memory inside the television, storing the resolution supported by this TV, for example: 720P or 1080P, if source (DVD) The source (DVD) does not know what resolution to broadcast when the television is supported by the current connected TV's resolution. Therefore, at the beginning of the source (DVD) through the two feet to read the resolution supported by the TV, when the source (DVD) know the source (DVD) to broadcast a video image that matches the TV resolution. Where the SCL is the clock pin, SDA is the data pin bit.

4.DVI Turn HDMI
Because HDMI and DVI use the same TMDS signal, it is easy to convert each other.

However, DVI does not specify the transmission of audio signals, so dvi to HDMI, or HDMI to DVI only video signal, no audio signal.
AMD's APU is a special case, the DVI signal from the APU platform is from HDMI, so the DVI interface with DVI transfer HDMI also has an audio signal.

Four, HDMI 1.4 new features
The latest version of HDMI is 1.4, and the new features of version 1.4 are described below.
1.HDMI Ethernet Channel (HDMI Ethernet CHANNEL,HEC)
HDMI version 1.4 Data cable will add a data channel to support high-speed bidirectional communication. Connected devices that support this feature can send and receive data over Gigabit Ethernet to meet any IP-based application.

The HDMI Ethernet channel will allow Internet-based HDMI devices and other HDMI devices to share Internet access without having to connect to another Ethernet cable. The new feature also provides a connectivity platform that allows content to be shared between HDMI devices.
HDMI Ethernet channel technology integrates video, audio, and data streams in a single HDMI cable, combining the best-in-class signal quality and convenience of HDMI connectivity with the powerful and resilient capabilities of home entertainment networks. The HDMI Ethernet channel adds a dedicated data channel to the HDMI connection, providing bidirectional high-speed network capabilities up to Mb/sec.
2. Audio Return Channel (CHANNEL,ARC)
A TV with a built-in tuner and HDMI interface allows you to "upload" audio data to the surround sound system without the use of other audio cables. In the case of HDTV directly receiving audio and video content, this new channel allows HDTV to transmit audio directly to A/V receiver via an HDMI cable, without the need for another cable.

3.HDMI 3D function
The new specification will define common 3D formats and resolutions for HDMI devices, standardize the input and output portion of the home 3D system, and support up to two 1080p resolution video streams.
With the rapid development of 3D technology, along with several competing technologies, the HDMI 1.4 specification defines the relevant protocols for common 3D display technologies, including: frame, graph, and field options, side-by method (panorama and half-view), and 2D plus depth method.

4. Support for higher resolution
HDMI devices support HD resolution of up to 4KX2K, four times times the current 1080p, capable of transmitting content at the same resolution as many digital home theaters.

Specific format: 3840x2160 24hz/25hz/30hz;4096x2160 24Hz.
5. Expand Support Color Space
HDMI technology will support the color space designed for digital cameras, including sYCC601, Adobe RGB, and AdobeYCC601 to show more accurate, realistic colors when connecting to digital cameras.
6.Micro HDMI Mini Interface
The new micro HDMI interface will be about 50% smaller than the current 19-pin Mini HDMI version, bringing up to 1080p resolution support and the fastest 5GB transfer speed for portable devices such as cameras and mobile phones.

7. Automotive Connection System (Automotive Connection System,acs)
A cable specification designed for in-vehicle HD content transmission avoids the effects of heat, vibration, noise, and other common internal environments, and provides a practical solution for vehicle manufacturers to deliver high-definition content within their vehicles.
Automotive connection version for HDMI E TYPE

8. Five kinds of HDMI1.4 new logo
Today, HDMI seems to be synonymous with high definition standards. Whether it is in the LCD TV, Blu-ray player, or HTPC, projector, this small interface is essential, with it means that this device into the sub-era of the ranks of the media player. And just as most people are debating whether the more advanced display port will replace HDMI, the HDMI1.4 version comes quietly. However, although the new version of HDMI added a lot of features, but not every technology is necessary, so in order to allow consumers to clearly function, not to spend money, recently, the HDMI Standard Authority issued a new specification for version 1.4.
According to the instructions of the HDMI standard authority, from now on, for those HDMI cable manufacturers in the sale and promotion of the new version, the prohibition of the use of the general version number identification, and the old version should be removed in one year all version number identification label, description, packaging and so on.

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Additional Information
Both DVI and HDMI are TMDS signal protocols.
HDMI TMDS signal includes video and HD audio, DVI only video. This is the difference between them.
This can occur in 2:
One is:
Integrated graphics design, if DVI and HDMI are designed separately, so that the DVI TMDS signal is not HD audio,
Only the HDMI TMDS signal is HD audio. Such a DVI interface is transferred to HDMI via DVI-HDMI without HD audio signal.
Intel's integrated graphics, AMD's 785, 880 set of integrated, as well as AMD and NV's discrete graphics are designed this way.
The other is:
Integrated graphics in HDMI design, TMDS signal includes video and HD audio,
DVI is transferred from HDMI,
Such a DVI interface via DVI-HDMI to HDMI will contain HD audio signal.
This is how AMD's APU is designed.
HDMI interface with HDMI protocol

What is an HDMI interface?

The English full name of HDMI is "High Definition multimedia", the Chinese meaning is the HD multimedia interface. The HDMI interface provides up to 5Gbps of data transmission bandwidth, which transmits uncompressed audio signals and high-resolution video signals. It also eliminates the need for a number/modulus or modulo/number conversion prior to signal transmission, guaranteeing the highest quality audio and video signal transmission. The advantage of applying HDMI is that only one HDMI cable is required, and the audio and video signals can be transmitted simultaneously, rather than requiring more than a few wires to connect, and that the wireless can achieve a higher quality of transmission due to digital/analog or analog/digital conversion. For consumers, HDMI technology not only provides clear picture quality, but also simplifies the installation of home theater systems due to the same cable used in audio/video.

2002 April, Hitachi, Panasonic, Philips, Silicon Image, Sony, Thomson, Toshiba a total of 7 companies set up the HDMI organization began to develop a new dedicated to digital video/audio transmission standards. The end of 2002, the high-definition digital multimedia interface (high-definition digitally multimedia Interface) HDMI 1.0 Standard promulgated. HDMI is compatible with DVI on the pin and is only used in different packages. Compared to DVI, HDMI transmits digital audio signals and adds support for HDCP, while providing better DDC optional functionality. HDMI supports 5Gbps data transfer rates up to 15 meters long enough to handle a 1080p video and a 8-channel audio signal. And because a 1080p video and a 8-channel audio signal demand less than 4gb/s, HDMI also has a very dayu amount. This allows it to connect DVD players, receivers and PRR with a single cable. In addition, HDMI supports EDID, DDC2B, so the device with HDMI has "Plug and Play" features, the signal source and display devices will automatically "negotiate", automatically select the most appropriate video/audio format.

Traditional AV composite and chromatic aberration interface both need separate audio and video data cable to transmit the signal, the same as the digital interface of the DVI interface does not support audio transmission, currently only HDMI has the ability to transmit audio and video signals on a single data line, so people are also accustomed to HDMI called "high-definition line."

What is HDCP protocol?

HDCP is the abbreviation of High-bandwidth Digital Content protection, which can be called "HDCP data Protection". HDCP Technology is a collaboration between Hollywood and the semiconductor giants Intel, it can be used in the video card, DVD player and other transmission end, as well as the display, TV, projector, the receiving end. is an important anti-piracy technology for high-definition movies and TV programs, the display that does not support HDCP protocol does not play the copyrighted high-definition program properly.

The HD movie program behind the DVD uses HDCP and AACS anti-piracy technology, both Blu-ray and HD DVDs Use this anti-piracy technology, and high-definition televisions (HDTV) are also used. With the use of HDCP and AACS anti-piracy technology, movie programs can only play on the device that supports HDCP, otherwise only see the black screen display or low-quality display (only about One-fourth of the normal definition), also handy lost the value of HD. AACS is a cryptographic technology that is used in HD DVDs and Blu-ray discs to protect the video content of the disc from being copied and played elsewhere.

The HDCP protocol is used to prevent the video content from being completely copied in the process of transmission. This technique does not allow digital signals to be recorded illegally, but to encrypt digital signals so that the non-legal recording method cannot achieve the original high-resolution quality. Blu-ray players, for example, cannot record a clear program while playing a high-definition disc while playing a disc on a computer without clearly recording the program on the Monitor. HDCP from the beginning to the end of the protection of the video signal, that is, the entire play system each link must support the HDCP protocol, if the display does not support HDCP protocol, then can not play normal HD programs, only to see the black screen or low-quality programs. To support HDCP protocol, it is necessary to use DVI, HDMI and other digital video interface, traditional VGA and other analog signal interface can not support HDCP protocol. When using the analog signal interface such as VGA, the screen will be reduced to a low quality, or the hint can not play, thereby losing the meaning of HD, to prevent piracy. It should be stated that the HDMI interface is embedded with the HDCP protocol, and the display with the HDMI interface supports the HDCP protocol. But not the LCD with DVI interface Support HDCP protocol, must pass with the corresponding hardware chip, through the certified display.

The data content protected by HDCP technology on the computer platform will be verified by the COPP driver (authentication Output Protection protocol) in the operating system first to verify the video card, only the legitimate video card can achieve the content output, and then to authenticate the display device key, Only HDCP-compliant devices can ultimately display the content that the video card transmits. In the process of HDCP transmission, both the sender and the receiver store an available key set, which are secret stores, both the sender and the receiver are encrypted and decrypted according to the key, and a special value KSV (video encryption key) is added to the operation. At the same time HDCP each device will have a unique KSV serial number, the sender and the receiving end of the password processing unit will check the other's KSV value, to ensure that the connection is legitimate. HDCP encryption process for each pixel processing, so that the picture becomes irregular, unrecognized, only after confirming the synchronization of the sending and receiving end can reverse processing, complete the restoration of data. During the decryption process, the HDCP system will make a connection confirmation every 2 seconds while the sender and receiver sync identifiers are sent every 128 frames to ensure the synchronization of the connection. In order to deal with key leaks, HDCP has specifically established a "revoke key" mechanism. The key set KSV value for each device is unique, and the HDCP system will compare and find it in the revocation list after receiving the KSV value, and the KSV appearing in the list will be illegal, leading to the failure of the authentication process. The revocation key list will be included in the multimedia data for HDCP and will be updated automatically.

It can be seen that in order to play copyrighted high-definition programs on your computer, whether it's HDTV, Blu-ray, or HD DVD, the monitor and graphics cards are required to support the HDCP protocol. But manufacturers to the product to play HDCP logo, you need to pay a certain amount of certification fees, but also to increase the hardware chip, obviously raised the cost, at present only some products through certification. Because of the popularity of high-definition programs, HDCP is a foregone conclusion, so support HDCP protocol devices will be more and more.

Full decryption of HDMI interface technology

Mention the interface of digital products, we can enumerate a large, what s terminal, AV terminal, chromatic aberration component interface, VGA interface, DVI interface ... When it comes to HDMI digital interface, consumers are not unfamiliar, as the latest generation of digital interface, HDMI has been widely used in a variety of digital products, whether it is flat-screen TV, DVD player, HD player, projector, digital camera, LCD display, as well as Blu-ray DVD and HD DVD, HDMI digital signal interface is indispensable.

Consumers of the advantages of the HDMI interface are very understanding, the author is not prepared to introduce, why the HDMI interface has these advantages may not be clear, the HDMI interface in the privacy of the data technology has won the praise of many enterprises, then in the end it has what characteristics, the following will give everyone to solve the mystery.

Basic transmission principle of HDMI

The HDMI (high-definition multimedia Interface), also known as the high-definition multimedia interface, is the first digital interface that supports all digital high-definition, multichannel audio, and intelligent format and control command data that is transmitted over a single cable without compression. The HDMI interface was developed by Silicon Image USA, a joint team of eight renowned consumer electronics manufacturers, including Sony, Hitachi, Panasonic, Philips, Thomson, Toshiba, etc. HDMI's earliest interface specification, HDMI1.0, was published in December 2002, and the current highest version is the HDMI1.3 specification released this June.

HDMI originates from the DVI interface technology, which is mainly based on the TMDS signal transmission technology of the American Crystal Image company, which is why the HDMI interface and the DVI interface can be converted to each other through the adapter. The American Crystal Image Company is the only IC design and manufacturing company in the HDMI eight initiator, is the leader in the field of high-speed serial data transmission technology, because the TMDS signal transmission technology mentioned below is what they developed, so here is a little mention.

TMDS (Transition minimized differential signaling) is also known as the minimized transmission differential signal, refers to the original signal data is converted to 10-bit through an XOR and XOR logic algorithm, the first 8 is the data from the original signal after the calculation, the 9th Bit indicates the way of operation, the 10th bit is used to correspond to the DC balance (dc-balanced, that is, in the encoding process to ensure that the channel DC offset to zero, level conversion to achieve a different logical interface between the matching), the converted data transmission by differential drive. This algorithm reduces the overshoot and undershoot of the transmitted signal transition process, and the transmitted data tends to be DC balanced, which reduces the electromagnetic interference of the signal to the transmission line, and improves the speed and reliability of the signal transmission.

In general, the HDMI connection consists of a pair of signal sources and receiver, sometimes a system can also contain multiple HDMI input or output devices. Each HDMI signal input interface can be based on the standard receive connector information, the same signal output interface will carry all the signal information. The HDMI cable and receiver includes three different TMDS data information channels and a clock channel that supports video, audio data and additional information, and video, audio data, and additional information is transmitted over three channels to the receiver, while the pixel clock of the video is transmitted via the TMDS clock channel. After the receiver accepts this frequency parameter, it restores the information passed by the other three data information channels.

Video and audio signal transmission

The source encoding format of the HDMI input includes video pixel data, control data, and data packets. The data packet contains audio data and auxiliary information data, and HDMI in order to obtain sound data and control data of high reliability, the packet also includes a BCH error correction code. HDMI data processing can be in many different ways, but ultimately in each of the TMDS channel contains 2-bit control data, 8-bit video data and 4-bit packets. The data transmission process of HDMI can be divided into three parts: video data transmission period, island data transmission period and control data transmission period.

HDMI data transmission, HDMI has three TMDS data information channel

Video data transmission period, the HDMI data line transmits the video pixel signal, the video signal is encoded, generates 3 channels (namely 3 TMDS data Information channel, each road 8 bits) altogether 24 bits of video data stream, enters into the HDMI emitter. The 24-bit pixel video signal is transmitted through the TMDS channel, the signal encoding of 8 bits per channel is converted to 10 bits, a minimized signal sequence is transmitted at each 10-bit pixel clock cycle, the video signal is modulated to transmit the TMDS data signal, and finally is received in the receiver.

The island data transfer period, audio data and auxiliary data will appear on the TMDs channel, each of which is a group of 4 bits, constituting a 4-bit packet mentioned above, and the same as the video data, is modulated to 10-bit a set of TMDS signal after the issue. The video data transmission period and the island data transmission period both begin in a guard band Protection band, Guard band is composed of 2 special characters, so the purpose of the design is to explicitly limit the control data transmission period after the jump is the video data transmission period.

HDMI data transmission period: Left to right respectively for the control data transmission period, the island data transmission period, video data transmission period

Control the data transfer period, between any of the above two data transmission cycles, each TMDS channel contains 2-bit control data, the total 6-bit control data is HSync (line synchronization), VSYNC (field synchronization), CTL0, CTL1, CTL2 and CTL3. Each TMDS channel contains 2-bit control data, using a 2-bit to 10-bit encoding method, at the last stage of each control cycle, a file header consisting of CTL0, CTL1, CTL2, and CTL3, indicating whether the next cycle is a video data transfer period or an island data transfer period.

The transmission of island data and control data is the blanking period of video data transmission, which means that when transmitting audio data and other auxiliary data, it does not occupy the bandwidth of video data transmission, and does not have a separate channel to transmit audio data and other auxiliary data. This is why an HDMI cable can simultaneously transmit video and audio signals.

HDMI high-pitched video bandwidth

HDMI data processing can be in a number of different ways, that is, HMDI supports a variety of ways of video coding, through a reasonable allocation of 3 TMDS data information channels, can transmit the RGB digital chroma component 4:4:4 signal, The 4:2:2 signal of the YCBCR digital chromatic aberration component can also be transmitted, which can meet the transmission needs of the 24-bit video signal.

HDMI per tmds channel video pixel stream rate is generally between 25mhz~165mhz, the HDMI1.3 specification has raised this limit to 225MHz, when the video format rate is less than 25MHz, the pixel repetition will be used to transfer, that is, the pixel in the video stream is reused. With a frequency of up to 165MHz per TMDS channel, 3 TMDS channels transmit r/g/b or Y/CB/CR encoded 24-bit pixel video data, The maximum bandwidth can reach 4.95Gbps, the actual video signal transmission bandwidth is close to 4Gbps, and now the highest standard HD video format The bandwidth required for the 1080p is only 2.2Gbps, so HDMI has enough bandwidth not only to meet the needs of today's HD video, but also to provide support for higher definition video formats over a long period of time.

In addition to the high video signal bandwidth, HDMI also adds support for audio signal transmission in the protocol, forming the industry's first single-wire multimedia interface protocol. HDMI audio signals do not occupy an additional channel, but are used together with other ancillary information to form a packet, using 3 TMDS channels in the video signal transmission of the blanking period, in the form of island data transmission. Even when transmitting a 1080p (60HZ) video signal, it can provide up to 8 high-quality audio signals per sample frequency of 192kHz, in contrast to the two-channel signal of the CD audio format 44.1kHz, and the latest Dvd-audio audio formats 96kHz 6-channel signal , it dwarfs it.

HDMI interface and protocol

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