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Digital Video Q&A
DVI Tutorial
1)
What is the difference between Dual Link and Single Link?
Dual link enables a higher resolution (1920 X 1080) and more channels. You can
view 2 displays simultaneously.
2) I need a DVI-I to DVI-D cable - What part number do I buy?
A DVI-I enables digital and analog signals. A DVI-D only allows digital
signals. The part number to buy is DVIDL-length
3) Why are your DVI cables so much less?
You are coming right to the source. Our cables meet all wiring specifications.
We don't know why everybody else is so expensive.
4) Is there a distance limitation?
Yes. For digital DVI cables there is a 5 Meter distance limitation.
5) What is the TFT LCD?
TFT stands for "Thin Film Transistor" and describes the control elements that
actively control the individual pixels. For this reason, one speaks of
so-called "active matrix TFT's". LCD means "Liquid Crystal Display" and stands
for monitors that are based on liquid crystals.
6) What's the difference between CRTs size and TFT size?
The visible diagonal size of a CRT tub monitor is always smaller than the
tube's actual diagonal size. For example: a 17-inch CRT monitor has an edge
area and it's visible diagonal is only 16-inches. But TFT LCD monitors do not
have an edge area. This means that a 15-inch TFT LCD monitor is almost the
same as the 17-inch CRT monitor.
7) What's the Contrast Ratio?
The Contrast Ratio is derived from the maximum and the minimum values for
brightness.
8) What's the difference between Digital and Analog Interface? Any
advantages or disadvantages?
TFT LCD monitors with an analog VGA interface dominate the market. Because it
is easy to install PC basis and not purchase a new graphics board. Although
digital TFT LCD monitors don't need to adjust clock and phase and the no
signal losses advantage. The Digital Interface standard has totally different
connectors and it is not easy to buy a suitable graphic board. So the analog
TFT LCD monitors still dominate the market. The following table gived you an
overview of the most important points:
| Digital Control |
Analog Control |
Advantages
- No signal losses due to DA and AD conversion
- Geometry, clock and phase settings unnecessary - therefore simple to
use
- Lower costs as less electronic circuitry required
Disadvantages
- Currently three standards (P&D, DFP, and DVI)
- Low availability of models with digital interfaces
- Requires graphic board with digital output
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Advantages
- Compatible with standard VGA boards on a broad installed PC basis
- Not necessary to purchase seperate board
Disadvantages
- Clock and phase of the TFTs must be synchronized with the analog
signal to avoid pixel jitter, which is a relatively complex issue
- Cables sensitive to external influences
- High cost of signal conversion inside the display
- Upgrade to digital interface not possible
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9) How many Digital Interfaces are there now? Which one do I choose?
Currently there are three digital interface standards (P&D, DFP, and DVI) in
the market. The following table is the comparison and summary of the three
interface standards. According to the table, DVI will be a standard in the
future. DVI not only allows high resolutions, it also enables the connection
of analog devices.
| Standard |
P&D |
DFP |
DVI |
| Owner |
VESA (Video Electronics Standards Organization) |
DFP Group (Digital Flat Panel Group) and later VESA |
DDWG (Digital Display Working Group) |
| Revision / Date |
1.0 / Jun 06, 1997 |
1.0 / Feb 14, 1999 |
1.0 / Apr 02, 1999 |
| Web page |
www.vesa.org |
www.dfp-group.org |
www.ddwg.org |
| Workgroup leader |
VESA |
Compaq |
Intel |
| Compatibility |
Own standard |
P&D compatible (adapter possible) |
P&D and DFP compatible (adapter possible) |
| Transfer protocol |
TMDS - Transmission Minimizing Differential Signaling (PanelLink) |
TMDS (PanelLink) |
TMDS (PanelLink) |
| Max. Pixel rate (Dot Clock) |
165 MHz x 1 |
165 MHz x 1 |
165 MHz x 1 |
| Max. number of channels |
3 channels (single link) |
3 channels (single link) |
6 channels (dual link) |
| Color depths |
12 or 24 bit |
12 or 24 bit |
12 or 24 bit |
| Max. Resolution |
SXGA (1280 x 1024) |
SXGA (1280 x 1024) |
HDTV (1920 x 1080) |
| Optional transfer of other signals possible using the same
connector |
Analog VESA video, USB, IEEE 1394-1995 |
No, only digital video |
Analog VESA video |
| Digital Connector |
P&D-D (30 pin) |
MDR20 (20 pin) |
DVI-V (24 pin) |
| Analog/Digital combination connector |
P&D-a/d (30+4 pin) |
No |
DVI-I (24 + 4 pin) |
| Connector width |
40.6 mm |
33.4 mm |
37.0 mm |
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