HDMI
HDMI (High-Definition Multimedia Interface) is a proprietary digital audio/video interface standard for transmitting uncompressed video and compressed or uncompressed audio between devices. Introduced in December 2002 (version 1.0), HDMI was developed by a consortium of electronics manufacturers including Sony, Hitachi, Panasonic, Philips, Toshiba, Silicon Image, and Thomson (RCA) to replace older analog video standards. HDMI became the dominant digital connection on consumer displays from the late 2000s onward, and was the last major video interface to appear on CRT televisions before their discontinuation.
History
HDMI was developed to address the limitations of existing interfaces in the transition from analog to digital consumer video. The Digital Display Working Group had released the DVI specification in 1999, but DVI connectors were large, carried no audio, and were oriented toward the computer market. The HDMI founders sought a compact, consumer-friendly connector that could carry both high-definition video and multi-channel digital audio over a single cable.[1]
HDMI 1.0, released in December 2002, supported resolutions up to 1080p at 60 Hz with a bandwidth of 4.95 Gbit/s, along with up to eight channels of uncompressed digital audio. The first consumer devices with HDMI ports appeared in 2003. Subsequent versions added features: HDMI 1.3 (2006) increased bandwidth to 10.2 Gbit/s and added deep color support; HDMI 1.4 (2009) introduced 4K resolution support (at 24–30 Hz) and the Audio Return Channel (ARC); HDMI 2.0 (2013) enabled 4K at 60 Hz with 18 Gbit/s bandwidth; and HDMI 2.1 (2017) pushed bandwidth to 48 Gbit/s for 4K at 120 Hz and 8K at 60 Hz.[1]
By 2008, HDMI-enabled device shipments exceeded those of DVI, and by 2009 all new HDTVs included at least one HDMI port. The standard has been adopted in over 10 billion devices worldwide.
Signal Characteristics
HDMI transmits digital video and audio data using Transition-Minimized Differential Signaling (TMDS), the same underlying protocol used by DVI-D. The TMDS link consists of three data channels (carrying red, green, and blue pixel data) plus a clock channel, all transmitted over shielded twisted-pair conductors within the HDMI cable.[1]
Key technical parameters include:
| Parameter | Value |
|---|---|
| Signal type | Digital (TMDS encoding; FRL in HDMI 2.1+) |
| Video | Uncompressed (or Display Stream Compression in 2.1) |
| Audio | Up to 32 channels (HDMI 2.0+); PCM, Dolby TrueHD, DTS-HD Master Audio |
| Color depth | 24-bit (8 bpc); 30/36/48-bit deep color (HDMI 1.3+) |
| Max bandwidth | 4.95 Gbit/s (1.0), 10.2 Gbit/s (1.3), 18 Gbit/s (2.0), 48 Gbit/s (2.1) |
| Content protection | HDCP 1.x / 2.x |
| Connector types | Type A (standard), Type C (mini), Type D (micro) |
| DVI compatibility | Electrically compatible with DVI-D via passive adapter (video only) |
HDMI is electrically compatible with the DVI-D digital interface. A passive adapter can connect an HDMI source to a DVI-D display (or vice versa) without signal conversion, though audio and HDMI-specific features like CEC are not carried over DVI.
Use on CRT Televisions
HDMI appeared on CRT televisions only during the very last years of CRT production, roughly 2004–2007. By the time HDMI became widespread, the consumer electronics industry was rapidly transitioning to flat-panel LCD and plasma displays, so relatively few CRT models ever received HDMI inputs. The CRT sets that did include HDMI were exclusively high-definition widescreen models — typically 30" and larger — capable of displaying 480p, 720p, and 1080i signals.
Notable examples of CRT televisions with HDMI inputs include certain late-model Sony WEGA HD CRTs (using the DA4 chassis with an internal DVI/HDMI decoder board), Samsung SlimFit HD CRTs, and select JVC and Toshiba HD models. On many of these sets, the HDMI input was implemented via a separate internal decoder board (such as Sony's "UD board") that converted the digital HDMI signal to analog YPbPr for the CRT's analog video processing pipeline.
For the CRT enthusiast community, HDMI-equipped CRT televisions are notable because they allow direct connection of modern digital sources (Blu-ray players, streaming devices, modern game consoles) without requiring an external HDMI-to-component converter. However, HDCP (High-bandwidth Digital Content Protection) can be problematic on some CRT sets, as older HDMI implementations may not support current HDCP versions, preventing playback of protected content from newer devices.
Because HDMI-equipped CRTs are uncommon, many CRT enthusiasts instead use external HDMI-to-component converters (such as the HD Fury series) to connect modern HDMI sources to CRT televisions that have component inputs but lack HDMI.
See Also
- DVI-D — Electrically compatible digital video interface
- Component (YPbPr) — Analog HD connection common on CRT HDTVs
- RGBS — Analog RGB signal format
- VGA (RGBHV) — Analog RGBHV computer display interface
