Suggestions: a circuit which converts digital video signals from a DVI for output on a display mediu

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I would like the hear others' views regarding such a design. It works
something like this: since a normal DVI for our purpose consists of
25-pins (24 pins representing a pixel being 24-bpp with 8-bits per
color plus one extra pin for clock) each pixel can be seperated by
channel (RGB) and fed as a sample into three consequitive DACs during
the scanning of a frame. When the value of the three 8-bit colors is
fed into the three DACs repectively, the analogue signal that is
produced from the outputs of the three DACs is then sent through the
three seperate RGB guns in a CRT while scanning a frame. With good
timing considerations, a good picture will be produced in time.

A diagram has also been demonstrated below:

___
/ |

24-pin DVI + 1 CLK / |
_ / |
| \ RED CHANNEL +===== R --- |
- | o-- ------- | +== G | CRT |
- |======== . . . . . o--| 8-bit | | | +=B --- |
- |======== . . . . . o--| |----O ====== | | \ |
- | o--| DAC | | | \ |
| / o-- ------- | | \___|
- | |
GREEN CHANNEL | |
o-- ------- | |
o--| | | |
INPUT ==>> o--| |----O ========+ |
o--| | |
o-- ------- |
|
BLUE CHANNEL |
o-- ------- |
o--| | |
o--| |----O =========+
o--| |
o-- -------
o = Digital Input
O = Analogue Output
.... = Trail

Suggestions are appreciated alongside any considerations that must be
taken account of for a design such as the above.

 

[Glenn Gundlach]

I would like the hear others' views regarding such a design. It works
something like this: since a normal DVI for our purpose consists of
25-pins (24 pins representing a pixel being 24-bpp with 8-bits per
color plus one extra pin for clock) each pixel can be seperated by
channel (RGB) and fed as a sample into three consequitive DACs during
the scanning of a frame. When the value of the three 8-bit colors is
fed into the three DACs repectively, the analogue signal that is
produced from the outputs of the three DACs is then sent through the
three seperate RGB guns in a CRT while scanning a frame. With good
timing considerations, a good picture will be produced in time.

A diagram has also been demonstrated below:

___
/ |

24-pin DVI + 1 CLK / |
_ / |
| \ RED CHANNEL +===== R --- |
- | o-- ------- | +== G | CRT |
- |======== . . . . . o--| 8-bit | | | +=B --- |
- |======== . . . . . o--| |----O ====== | | \ |
- | o--| DAC | | | \ |
| / o-- ------- | | \___|
- | |
GREEN CHANNEL | |
o-- ------- | |
o--| | | |
INPUT ==>> o--| |----O ========+ |
o--| | |
o-- ------- |
|
BLUE CHANNEL |
o-- ------- |
o--| | |
o--| |----O =========+
o--| |
o-- -------
o = Digital Input
O = Analogue Output
... = Trail

Suggestions are appreciated alongside any considerations that must be
taken account of for a design such as the above.

You're quite correct. In fact, I'm looking at one right now. It's
called (Rich, did I use the apostrophe correctly?) a video card. The
DVI connector is simply a means to move the digital data off board to
another. All video cards with a VGA connector have RGB DACs on board
(with a little longer cable than you imagine in your description). With
good coax cable and properly interfaced in the analog world, you would
not be able to see the difference.

Now for a DLP or LCD, the digital data is converted to PWM to get
variable (analog) intensity but does the same task as the DAC to CRT.

Sorry to rain on your parade. It's been done.

GG

 

[Paul Hovnanian P.E.]

[snip]

You're quite correct. In fact, I'm looking at one right now. It's
called (Rich, did I use the apostrophe correctly?) a video card. The
DVI connector is simply a means to move the digital data off board to
another. All video cards with a VGA connector have RGB DACs on board
(with a little longer cable than you imagine in your description). With
good coax cable and properly interfaced in the analog world, you would
not be able to see the difference.

Now for a DLP or LCD, the digital data is converted to PWM to get
variable (analog) intensity but does the same task as the DAC to CRT.

Sorry to rain on your parade. It's been done.

It can't be that tricky. Apple sells their mini Mac with only a DVI
output. They give you a little DVI to VGA dongle that is a little over
an inch long and just wide and high enough for the connectors on either
end.

--
Paul Hovnanian mailto[email protected]
------------------------------------------------------------------
The opinions stated herein are the sole property of the author. All
rights
reserved. Void where prohibited. For external use only. Standard
disclaimers
apply. If irritation, rash or swelling occurs, discontinue use
immediately
and consult a physician.

 

[Don Bowey]

[snip]

You're quite correct. In fact, I'm looking at one right now. It's
called (Rich, did I use the apostrophe correctly?) a video card. The
DVI connector is simply a means to move the digital data off board to
another. All video cards with a VGA connector have RGB DACs on board
(with a little longer cable than you imagine in your description). With
good coax cable and properly interfaced in the analog world, you would
not be able to see the difference.

Now for a DLP or LCD, the digital data is converted to PWM to get
variable (analog) intensity but does the same task as the DAC to CRT.

Sorry to rain on your parade. It's been done.

It can't be that tricky. Apple sells their mini Mac with only a DVI
output. They give you a little DVI to VGA dongle that is a little over
an inch long and just wide and high enough for the connectors on either
end.

My Apple video converter is somewhat larger, having about a 4" cable to a
head which outputs composite video and audio. In my opinion the video
quality is very poor. Obviously another Apple "Think Different," and think
cheap.

Don



Don

 

[Sylvain Munaut]

Glenn Gundlach wrote:

[snip]

You're quite correct. In fact, I'm looking at one right now. It's
called (Rich, did I use the apostrophe correctly?) a video card. The
DVI connector is simply a means to move the digital data off board to
another. All video cards with a VGA connector have RGB DACs on board
(with a little longer cable than you imagine in your description). With
good coax cable and properly interfaced in the analog world, you would
not be able to see the difference.

Now for a DLP or LCD, the digital data is converted to PWM to get
variable (analog) intensity but does the same task as the DAC to CRT.

Sorry to rain on your parade. It's been done.

It can't be that tricky. Apple sells their mini Mac with only a DVI
output. They give you a little DVI to VGA dongle that is a little over
an inch long and just wide and high enough for the connectors on either
end.

On the DVI connectors, some of the pins are dedicated to analog output.
So the DVI out has both anolog and digital. You 'dongle' is just a few
wires to connect the good pins to the VGA connector.

 

[Apostrophe Police]

You're quite correct. In fact, I'm looking at one right now. It's
called (Rich, did I use the apostrophe correctly?)

Yup.

a video card. The

 

[Zak]

Now for a DLP or LCD, the digital data is converted to PWM to get
variable (analog) intensity but does the same task as the DAC to CRT.

A DLP is digital all the way to the mirror: the light is either on or off.


Thomas

 

[Glenn Gundlach]

A DLP is digital all the way to the mirror: the light is either on or off.


Thomas

That's right, it IS on or off, but to get the variable brightness, you
have to mimic the analog world. SO, the PWM. I stand by my comment that
the PWM does the same task as a DAC in this instance. That's all.

GG