What is an HDMI cable?


Time:

2021-11-09

HDMI is designed to replace older analog audio and video transmission terminals such as SCART or RCA. It supports a wide range of TV and computer video formats, including SDTV and HDTV video pictures, plus multi-channel digital audio.

What is an HDMI cable?

HDMI is designed to replace older analog audio and video transmission terminals such as SCART or RCA. It supports a wide range of TV and computer video formats, including SDTV and HDTV video pictures, plus multi-channel digital audio. HDMI and UDI without audio transmission function both inherit the core technology of DVI "transmission minimization differential signal" TMDS, which is still essentially an extension of DVI. The video content of DVI, HDMI, and UDI is transmitted in real-time, dedicated line mode, which can ensure that the video traffic will not be blocked. Each pixel has 24 bits of data. The timing of the signal is very similar to that of VGA. The images are sent line by line, and a specific blank time is added after each line and each frame is sent (similar to a simulation scan line). The data is not "Micro-Packet Architecture", and only the changed parts of the two frames before and after are updated. Each screen will be fully re-sent at this update. When the specifications were first developed, the maximum pixel transfer rate was 165Mpx/sec, enough to support 60 frames per second at 1080p, or UXGA resolution (1600x1200). It was later expanded to 340Mpx/ SEC in the HDMI 1.3 specification to match possible future demand.

However, DisplayPort was developed for LCD at the very beginning and adopted the transmission Architecture of "Micro-Packet architecture". Video content is transmitted in the form of data packet, which is obviously different from video transmission technologies such as DVI and HDMI. In other words, HDMI came to replace analog signal video, and DisplayPort came to replace DVI and VGA ports.

HDMI also supports uncompressed 8-channel Digital audio transmission (sample rate 192kHz, data length 24bits/sample), and any compressed audio streams such as Dolby Digital or DTS, as well as 8-channel 1bit DSD signals used by SACD. In the HDMI 1.3 specification, support for ultra-high data volume uncompressed 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 still no manufacturer uses the Type B connector. The Type B connector has 29 pins, allowing it to send extended video channels for future high quality demands such as the WQSXGA(3200x2048).

Type A HDMI is backward compatible with the Single-linkDVI-D or DVI-I interface used by most displays and graphics cards today (but not DVI-A), which means that a signal source using the DVI-D interface can drive the HDMI display through a converter cable. However, this conversion solution does not support audio transmission and remote control. In addition, DVI displays without HDCP certification will not be able to view the HDCP encrypted video data output from HDMI (all HDMI displays support HDCP, but most DVI displays do not support HDCP). The Type B HDMI connector will also be backward compatible with the Dual-link DVI interface.

The initiators of the HDMI group include major consumer electronics manufacturers such as Hitachi, Panasonic, Quasar, Philips, SONY, Thomson RCA, Toshiba and Silicon Image. Digital Content Protection (LLC) offers copy-proof technology for HDMI ports. HDMI is also supported by major motion picture studios such as 20th Century Fox, Warner Bros., Disney, major consumer electronics manufacturers including Samsung Electronics, and a number of cable system companies.