HDMI (High Definition Multimedia Interface) is a fully digital video and audio transmission interface that can transmit uncompressed audio and video signals. HDMI can be used in set-top boxes, DVD players, personal computers, video game consoles, integrated amplifiers, digital audio and television sets. HDMI can transmit both audio and video signals. Since the audio and video signals use the same cable, the installation difficulty of the system circuit is greatly simplified.
HDMI is designed to replace older analog signal audio and video transmission interfaces such as SCART or RCA. It supports a variety of TV and computer video formats, including SDTV, HDTV video, plus multi-channel digital audio.Both HDMI and UDI with audio transmission removed inherit DVI’s core technology ‘Transfer Minimized Differential Signals’ TMDS, which is essentially an extension of DVI. The video content of DVI, HDMI and UDI are transmitted in an instant and dedicated way, which can ensure that the video traffic will not be blocked when it is large. The amount of data per pixel is 24 bits. The timing of the signal is very similar to VGA. The picture is sent line by line, and a specific blank time (similar to the analog scan line) is added after each line and each picture is sent, and the data is not ‘Micro-Packet Architecture’. It will not update only the parts of the two frames before and after the change. Each picture will be completely resent at the time of this update. The specification has a maximum pixel transfer rate of 165Mpx/sec at the beginning of formulating, which is enough to support 1080p image quality at 60 frames per second, or UXGA resolution (1600×1200); later it is expanded to 340Mpx/sec in the HDMI 1.3 specification to match the future possible demand.
DisplayPort was originally developed for LCD monitors. It uses the ‘Micro-Packet Architecture’ transmission architecture, and video content is transmitted in packets. This is clearly different from video transmission technologies such as DVI and HDMI. In other words, the emergence of HDMI replaced the analog signal video, and the emergence of DisplayPort replaced the DVI and VGA interfaces.
HDMI also supports uncompressed 8-channel digital audio transmission (sample rate 192kHz, data length 24bits/sample), as well as any compressed audio stream such as Dolby Digital or DTS, as well as 8-channel 1bit DSD signals used by SACD. In the HDMI 1.3 specification, the support of ultra-high-volume uncompressed audio streams such as Dolby TrueHD and DTS-HD are added.
The standard Type A HDMI connector has 19 pins, and a Type B connector that supports higher resolution is defined, but there are still no vendors using Type B connectors. The Type B connector has 29 pins that allow it to transmit an extended video channel to meet future high image quality requirements such as WQSXGA (3200×2048).
Type A HDMI is backward compatible with the Single-link DVI-D or DVI-I interface (but not DVI-A) used by most monitors and graphics cards today, which means that the signal source using the DVI-D interface can drive the HDMI display through conversion line, but this conversion scheme does not support audio transmission and remote control.In addition, if the DVI display is not HDCP-certified, video data with HDCP encryption protection output from HDMI will not be available (all HDMI displays support HDCP, but most DVI-based displays do not support HDCP), Type B HDMI connector will also be backward compatible with the Dual-link DVI interface.
The HDMI organization’s sponsors include major consumer electronics manufacturers such as Hitachi, Panasonic Electric, Quasar, Philips, Sony, Thomson, Toshiba, and Silicon Image. Digital Content Protection (LLD) provides HDMI-based copy protection technology. In addition, HDMI is also supported by major film production companies such as 20th Century Fox, Warner Bros., Disney, major consumer electronics manufacturers including Samsung Electronics, and a number of cable TV system operators.
After more than ten years of development, HDMI has been developed to version 2.1. The following are the release times for HDMI versions:
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HDMI VERSION |
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1.0-1.2a |
1.3-1.3a |
1.4-1.4b |
2.0-2.0b |
2.1 |
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Published
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2002.12（1.0） 2004.05（1.1) 2005.08（1.2） 2005.12 (1.2a) |
2006.06（1.3） 2006.11（1.3a） |
2009.06（1.4） 2010.03（1.4a） 2011.10（1.4b） |
2013.09（2.0） 2015.04（2.0a） 2016.03（2.0b） |
2017.11 |