HDMI

The High-Definition Multimedia Interface, commonly known as HDMI is a compact audio as well as video connector interface for transmitting uncompressed digital streams. It represents a digital alternative to consumer analog standards such as Radio Frequency or RF, coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, and VGA. HDMI connects digital audio/video sources such as set-top boxes, Blu-ray Disc players, personal computers, video game consoles, and AV receivers to compatible digital audio devices, computer monitors, and digital televisions. HDMI supports, on a single cable, any TV or PC video format including standard, enhanced, and high-definition video along with up to 8 channels of digital audio. HDMI products started shipping in autumn 2003 and currently over 800 CE and PC companies have adopted the HDMI specification, which are commonly known as HDMI Adopters. HDMI supports, on a single cable, any TV or PC video format including standard, enhanced, and high-definition video along with up to 8 channels of digital audio. HDMI encodes the video data into TMDS for uncompressed digital transmission over HDMI. HDMI supports 8 channel uncompressed digital audio at 192 kHz sample rate with 24 bits/sample as well as compressed audio streams such as Dolby Digital and DTS. HDMI supports up to 8 channels of one-bit DSD audio, which is used on Super Audio CDs, at rates up to 4x that of Super Audio CD. The HDMI cable can be used to carry video, audio, and device-controlling signals or CEC. HDMI cables are often more expensive than other video cables at retail stores. The HDMI specification does not define a maximum cable length but because of signal attenuation there is an upper limit to how long HDMI cables can be made. HDMI carries video, audio, and auxiliary data via one of three modes called the Video Data Period, the Data Island Period, and the Control Period. The Control Period occurs between Video and Data Island periods. The HDMI connection can either be single link or Type A/C or dual link or Type B and can have a video pixel rate of 25 MHz to 340 MHz for a single link connection or 680 MHz for a dual link connection. HDMI supports up to 8 channels of audio at sample sizes of 16-bit, 20-bit, and 24-bit with sample rates of 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, and 192 kHz. CSS, CPPM, and AACS require the use of HDCP on HDMI when playing back encrypted DVD-Video, DVD-Audio, and Blu-ray Disc. The HDCP Repeater bit controls the authentication and switching/distribution of an HDMI signal. Both HDMI and DVI use TMDS to send 10-bit characters that are encoded using 8b/10b encoding for the Video Data Period and 2b/10b encoding for the Control Period. HDMI adds the ability to send audio/auxiliary data using 4b/10b encoding for the Data Island Period. Each Packet contains four sub-packets each of which are 64-bits in size including 8-bits of BCH ECC parity data allowing for each Packet to carry up to 224-bits of audio data. Seven of the fifteen packet types described in the HDMI 1.3a specifications deal with audio data while 8 of the 15 Packet deal with auxiliary data. The CEC feature is used to allow the user to command and control multiple CEC-enabled boxes with one remote control and for individual CEC-enabled boxes to command and control each other without user intervention. No remote control command is needed.