HDMI is designed to replace older analog signal audio and video transmission interfaces such as SCART or RCA terminals. It supports various TV and computer video formats, including SDTV, HDTV video, plus multi-channel digital audio. Both HDMI and UDI without audio transmission function inherit the core technology of DVI “transmit minimum differential signal” TMDS, which is still an extension of DVI in essence. DVI, HDMI, UDI video content are transmitted in real-time, dedicated line mode, which can ensure that there will be no congestion when the video traffic is large. The amount of data per pixel is 24 bits. The timing of the signal is very similar to that of VGA. The picture is sent in a line by line manner, and a specific blank time (similar to analog scan line) is added after each line and frame of the picture are sent. The data is not “micro packet architecture” and will not only update the changed parts of the two frames. Each screen will be completely resend at the time of the update. When the specification is initially formulated, its maximum pixel transmission rate is 165mpx / sec, which is enough to support 1080p image quality of 60 pictures per second, or UXGA resolution (1600×1200); later, it is expanded to 340mpx / s in HDMI 1.3 specification to match the possible future requirements.
At the beginning, Display Port was developed for LCD, using “micro packet architecture” transmission architecture, and video content was transmitted in the form of data packets, which was obviously different from DVI, HDMI and other video transmission technologies. In other words, HDMI replaces analog video, while DisplayPort replaces 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. It also supports 8-channel 1-bit DSD signals used by SACD. In HDMI 1.3 specification, support for ultra-high data volume non compressed audio streams such as Dolby truehd and DTS-HD is added.
The standard type A HDMI connector has 19 pins, and a type B connector that supports higher resolution has been defined, but no manufacturer has used the type B connector. The type B connector has 29 pins, allowing it to send extended video channels to meet future high-quality requirements, such as WQSXGA (3200×2048).
Type A HDMI can be backward compatible with single link DVI-D or DVI-I interface (but not DVI-A) used by most displays and video cards. This means that the signal source using DVI-D interface can drive HDMI display through conversion line, but this conversion scheme does not support audio transmission and remote control function. In addition, if the DVI display screen without HDCP certification will not be able to view the video data with HDCP encryption protection output from HDMI (all HDMI displays support HDCP, but most displays with DVI interface do not support HDCP), the type B HDMI connector will also be backward compatible with dual link DVI interface.
HDMI’s founders include major consumer electronics manufacturers such as Hitachi, Panasonic, quasar, Philips, Sony, Thomson RCA, Toshiba, silicon image. Digital content protection,LLC provides anti copy protection technology related to HDMI interface. In addition, HDMI is also supported by major film production companies such as 20th century fox, Warner Brothers, Disney, major consumer electronics manufacturers including Samsung Electronics, and a number of cable TV system operators.
Post time: Dec-22-2020