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What is
DVI?
Why DVI?
How it
works?
Conectors
Cables
I
heard DVI is already dead.
What is HDCP?
So
what should I be doing today?
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What
is DVI?
The Digital Display
Working Group (DDWG), a coalition of consumer electronics and
semiconductor manufacturers, developed DVI (Digital Visual Interface)
to address the growing demand for direct digital connectivity between
source and display units.
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Why
DVI?
Today, most sources
(e.g., DVD, set-top box, video processor) operate in the digital
domain. Since many displays are also digital (DLP, LCD, plasma), it
doesn't make sense converting back and forth between analog and
digital (i.e., why endure signal degradation if you don't have to?)
Bypassing this unnecessary conversion creates noise-free images with
perfect colour and timing accuracy. Hence, the development of a
standard for connecting sources and displays digitally.
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How
it works
DVI is a video
interface, just like S-video or component. However, DVI can take
several forms. Some early DVI devices utilized DVI-A, a non-standard
analog-only connection. By far the most common form in consumer
electronics is DVI-D (digital only). The hybrid (analog and digital)
DVI-I appears primarily on computers and presentation projectors.
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For DVI-D and DVI-I,
single and dual link connections are available, with the only
distinction being bandwidth. Single link (165 MHz bandwidth) will
support up to 1920x1080 at 60 Hz or 1280x1024 at 85Hz. Dual link (330
MHz bandwidth) supports up to QXGA (2048x1536) at 60Hz or 1920x1080
at 85Hz. In other words, a single link DVI-D cable will support all
current HD formats. (Note: single link connectors will fit dual link
connectors, but the reverse is not true.)
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Connectors
Examples of the
different connectors are displayed below:
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DVI-A
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DVI-D Single Link
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DVI-D Dual Link
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DVI-I Single Link
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DVI-I Dual Link
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Just to complicate
matters, some manufacturers are utilizing proprietary connectors on
their displays. Specifically, InFocus (and InFocus-based projectors
like Toshiba) utilize an M1 digital connector. Several flat panels,
most notably those with separate "media centres", utilize
an MDR20 connector. Both are compatible with DVI through the use of
an adapter.
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Cables
The standard spec for
DVI is up to 5 metres (approximately 16 feet). Until recently, it was
simply not possible to extend beyond that distance. But with
increasing demand comes innovation: high quality copper and
fibre-optic cables are now available to transmit at much greater
distances. These cables are not inexpensive, but they represent the
only solution for long-run DVI scenarios.
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I
heard DVI is already dead.
Not true. Most digital
source and display units are currently shipping with DVI. As per the
norm for consumer electronics, competing formats are constantly being
developed. Firewire (IEEE 1394) is another form of digital
connectivity. However, it is primarily reserved for digital camera
connectivity. HDMI (High Definition Multimedia Interface), on the
other hand, is expected to ultimately replace DVI. HDMI offers a
smaller, user- (and conduit-) friendly connector with transfer speeds
up to 3 times that of DVI. The spec allows for uncompressed
high-bandwidth video and multi-channel audio: in essence, a single,
all-digital audio/video interconnect.
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What
is HDCP?
High-Bandwidth Digital
Content Protection is an encryption process to protect uncompressed
digital signals. Essentially, it's Hollywood's way of making sure we
don't share movies like we do audio. It is important to note that
non-HDCP-compliant devices will not work with HDCP-encoded material.
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So
what should I be doing today?
For now, you should be
pre-wiring your homes for DVI. Ensure that you are utilizing
cables appropriate for the resolution and distance! Conversely, you
can install 2-inch conduit to facilitate pulling any cable down the
road. It is important to note that HDMI is pin-for-pin compatible
with DVI.
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