The type of video interconnects you use will significantly affect the quality of video displayed on your HDTV. The type of video interconnect is especially important in the high definition realm since some interconnects do not carry HD video signals. Care must be taken when connecting or purchasing Home Theater Network equipment to make sure high quality video interconnects are available.
A common cause for confusion is that video interconnects and video signals are not always tied together. For example, a RCA interconnect can be used to carry either a component YPbPr video signal, or a composite video signal. These are two vastly different video signals, with the former being high definition and the latter being standard definition.
Below is a chart ranking the most common video signals with number one producing the highest quality video. The chart includes all the possible interconnects you can find with different video signals.
|Video Quality||Video Signal||Interconnect|
|1||Digital video signal||HDMI, DVI|
|2||RGB||VGA D-sub, BNC, RCA (very rarely)|
|3||Component (YPbPr or YCpCr)||RCA, BNC, VGA D-sub (very rarely), SCART|
|4||S-video||4 pin mini-DIN, 7 pin mini-DIN, SCART|
|5||composite||RCA, BNC, SCART|
HDMI (High Definition Multimedia Interface) is a user–friendly interconnect that carries digital video and digital audio signals. Think of HDMI as the USB of video and audio. USB is plug and play, and was designed to replace less customer–friendly interconnects. The HDMI interconnect is similar, as it was designed to reduce customer confusion from multiple surround sound audio Connections, and multiple versions of the Digital Video Interface (DVI) interconnect. HDMI supports high definition (720p, 1080i, and 1080p) as well as standard definition video. It also supports up to 8 channels of high-resolution digital audio. HDMI is backwards compatible with DVI, and supports up to 5 Gbps of bandwidth to help accommodate any future requirements.
There are different specifications for the HDMI interconnect. The chart below shows the differences in capabilities between the 1.2 HDMI spec and the latest 1.3 HDMI spec.
|Max Data Rate||4.95 Gb/s||10.2 Gb/s|
|Max Bandwidth||165 MHz||340 MHz|
|Max Resoltion/Framerate||1080p (UXGA)||1440p (WQXGA)|
|Max color bit depth||24 bits||48 bits|
|Maximum Colors||16.7 Million||281 Trillion|
|Supports DTS and Dolby Digital 5.1||Yes||Yes|
|Supports Dolby TrueHD and DTS-HD||No||Yes|
|Max Audio Sample Frequency
(2 channels only)
|192 kHz||768 kHz|
|Max Audio Sample Frequency
(3 to 8 channels)
(4 streams max)
(8 streams max)
Although HDMI is backwards compatible with DVI, problems sometimes occur when connecting the two together. The problems are due to HDMI having a built–in copyright protection called HDCP (High–bandwidth Digital Content Protection), while DVI carries its video signals unencrypted. Developed by Intel, HDCP requires “handshaking” between the source of the audio/video signal, and the receiver of the audio/video signal. For example, a cable set–top–box would send a signal to a HDTV checking to see if it is HDCP compliant. If it is, then the HDTV would send a signal (or handshake) back, which would allow the cable box to send audio/video to the HDTV. If it is not HDCP compliant (like most 2–3 year old HDTVs with DVI inputs), then the cable box will not receive a HDCP compliant handshake from the HDTV. The end result would be a blank screen, and no audio/video displayed on the HDTV. HDCP is even known to cause problems connecting HDMI devices to HDMI devices, due to syncing issues.
However, all these issues are happening less frequently as HDMI gains popularity. It is estimated by multiple sources that output for HDMI-enabled digital TV receivers will reach 15 million by the end of 2006 and up to 50 million by 2007. Its copyright protection is popular with the movie studios, and expect to see all HD DVD and Blu-ray players to have HDMI interconnects.
Click here for more information on HDMI’s audio capabilities.