HDMI Interface

HDMI interface

HDMI (High Definition Multimedia Interface) is a digital interface for transferring uncompressed, high-definition multimedia data (audio and video). Some have called it "high-definition SCART."

Initiated by a consortium of manufacturers including Hitachi, Matsushita, Philips, Silicon Image, Sony, Thomson and Toshiba, the HDMI interface was standardized in 2002 as version 1.0, then revised in May 2004 (version 1.1) and finally in August 2005 (version 1.2).

As time goes by, it will be included little by litle with audio and video equipment, which will carry this logo:


The HDMI standard brings with it a new compact connector, compatible with DVI (Digital Video Interface), which looks like this:

HDMI connector

Technical characteristics

In terms of capacity, the HDMI interface can reach speeds of about 5 Gbps (HDTV at 2.2Gbps). This can be used to transmit:

  • multichannel sound (up to 8 PCM channels at 24 bits/192 kHz) with a sampling rate of 32 kHz, 44.1kHz, 48kHz or 192kHz;
  • 24-bit high-definition video signals (up to 1920x1080) on three channels (8 bits per channel). The HDMI interface supports all current video formats and includes three new ones, in order to standardize equipment:
    • SDTV: 720x480i in NTSC, 720x576i in PAL;
    • EDTV: 640x480p in VGA, 720x480p in NTSC progressive, 720x576p in PAL progressive;
    • HDTV: 1280x720p, 1920x1080i

Protective measures

The DVI transports a native digital signal between the source and destination devices, which makes it easy to copy the multimedia stream. For this reason, the major film studios and music labels have made data encryption a requirement of the HDMI standard.

This mandatory copyright-protection mechanism is named HDCP (High Bandwidth Digital Content Protection).

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