the most common HDMI socket
the most common HDMI socket


HDMI is a fully digital audio/video interface that transmits uncompressed encrypted streams. HDMI is used to connect an audio/video source (DVD player, Blu~ray player, computer or game console) to a high~definition TV.

HDMI supports all video formats, including standard, enhanced, high~definition definition and multichannel sound.
HDMI encapsulates video data with TMDS.

Initially, the maximum HDMI transmission tau was 165 Mpixel/s, allowing the resolution to be transmitted 1080p to 60 Hz or UXGA (1600 x 1200) standard.
But the HDMI 1.3 standard has increased transmission to 340 Mpixel/s.
HDMI also transmits sound up to 8 uncompressed channels on a 192 KHz sampling tau with 24 bit/sample and compressed audio streams such as DTS and 'Dolby Digital surround'.
This data is also encapsulated in the TMDS transmission standard.
HDMI Type 1.3 adds support for very high~quality audio streams ~ (Lossless) ~ such as Dolby, TrueHD and DTS~HD Master Audio.

The standard Type A HDMI connector has 19 pins, and a higher resolution version of the connector called the Type B connector has also been set : the 29~pin Type B connector to support very high resolutions.

HDMI port of a laptop
HDMI port of a laptop

HDMI : important

HDMI uses a standardized process that organizes video data streams : TMDS . When the HDMI standard was created, the maximum speed and transmission speed were set at 165 Mpixel/s. This tau was high enough to provide video resolution up to 1080p to 60 Hz. Improved standard has resulted in transmission compatibility of up to 340 Mpixel/s.

an HDMI cable cut
an HDMI cable cut

Types of HDMI cables

Type A is retro~compatible with the DVI \Single~link\ which is widely used on graphics cards and computer monitors. This means that a transmitter, using the DVI~D standard, can direct a screen for the HDMI standard with an adapter and vice versa. Type B is retro~compatible with DVI Dual~link.

Most common resolution for different types of HDMI :
SDTV (Standard definition tv) : 720x480i (NTSC) 720x576i (PAL)
EDTV (Enhanced Definition TV) : 720x480p (progressive NTSC)
HDTV (high definition TV) : 1280x720p, 1920x1080i 1920x1080p

HDMI supports display of different frequencies (number of frames per second) : 24/25/30/50/60 Hz

Standard TMDS HDMI A

1 TMDS HDMI 2 data +
2 TMDS HDMI 2 armoured data
3 TMDS HDMI 2 Colors -
4 TMDS HDMI 1 data +
5 TMDS HDMI 1 armoured data
6 TMDS HDMI 1 data -
7 TMDS HDMI 0 data +
8 TMDS HDMI 0 armoured data
9 TMDS HDMI 0 data -
10 Clock + TMDS HDMI
11 TMDS HDMI armoured clock
12 Clock - TMDS HDMI
13 CEC
15 SCL
16 SDA
18 5 V voltage (MAX 50 mA)
19 Detection

all 3 types of HDMI connector
all 3 types of HDMI connector

HDMI Standards

The value of HDMI is based on the three definitions of HDTV. Version 1.3 also allows a 10~bit video~per~color transfer, offering a wider range of colors.
This revision adds support for 48~bit color depth.

The video transfer tau ranges from 25 MHz, 340 MHz (Type A, 1.3 standard) to 680 MHz (Type B).
Video formats with rates below 25 MHz are widely used due to pixel repetition.
The refreshment tau can reach 120 Hz.

The acronym SDTV means compatible with the standard ntSC, PAL or SECAM video standards.

Because the EDTV signal is progressive, it has a stronger sharpness than its SDTV equivalent and is not subject to de~interlacing artifacts. This gives much better results when displayed on an HDTV.

EDTV is the format used by DVD players who are in charge of deinterlating (progressive scanning) and by game consoles.
Be careful, even if the console allows it and it is connected and set correctly, not all games support this format.

HDMI TV shots
HDMI TV shots

Types of supported audio formats :

Uncompressed (PCM) : Audio PCM up to 8 channels at a 24~bit sampling rate with up to 192 kHz of frequency. Compressed : supports all common compressed formats; Dolby Digital 5.1~7.1, SDRs, etc.
SACD HDMI DVD~Audio (competitor of SACD HDMI)
HDMI has been supporting non~loss~of~quality formats (Lossless) since 1.1
HDMI supports the Dolby TrueHD and DTS~HD Master Audio found in HD DVD and Blu~ray formats.