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PICList Thread
'VGA RGB REAL-TIME FRAME GRABBER'
1998\06\06@184133 by Philibert Perusse

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Suppose this problem. You have to take an VGA 640x480 RGB signal where on
each color is mapped an grayscale image so we have
three differents images comings at 60Hz...What you have to do with this VGA
signal is to show it at 180Hz on a particular monochrome LCD display. You
have to show the three monochrome images that composed the VGA signal one
after the other. So lets look at
a solution of this problem.

I think that you must digitalize (GRAB) the 3 colors independently and
store them before to take them to the LCD one color frame at the time. So,
this problem is almost the same than to make a frame grabber that grab a VGA
signal and store it into any kind of memory (I do prefer to use FIFOs).
Moreover, the complete design must take place over a single 5"x4" board.
It's my solution but is someone has a better idea!!!!

So, here is MY problem. Is-it realistic to do this in 10 weeks (15 hours a
week) with a total cost (for each unit, not considering the development) of
maximum 500$ by unit?

I think not! (Considering that Cypress 128k FIFOs cost 150$ each) But I hope
I'm not wrong because I'll try to explain that to my boss!!!

(You've probably remark my poor english...is't because I'am a french
canadian!!!!)
                                                                           
                   Phil!
Philibert PŽrusse <spam_OUTperusseTakeThisOuTspamino.qc.ca>
INO
369, rue Franquet
Sainte-Foy, ( QuŽbec) Canada  G1P 4N8
tel: (418) 657-7006 Fax: (418) 657-7009
http://www.ino.qc.ca

1998\06\06@213733 by Barry Cooper

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>(You've probably remark my poor english...is't because I'am a french
>canadian!!!!)
>

 It's much better than my French!

       Barry

1998\06\07@100159 by g.daniel.invent.design

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Phil,
The FIFO does sound expensive,
here's another approach:

If you can get large enough "bucket brigade" charge coupled delay lines,
then using two per colour (six) you can simultanously scan one original
frame on three CCD chips, meanwhile, the other three CCD chips are
sequentially offloading their image at triple speed to the monochrome
input. OBTW, I presume all this trouble is due to strobed RGB
backlighting ? (It's always seemed a waste to me to have diferent pixels
for the RGB components)

I don't know about the time factor, but bosses have to have goals,
realistic or not.

regards,
Graham Daniel

Philibert Perusse wrote:
{Quote hidden}

1998\06\08@052729 by Russell McMahon

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-----Original Message-----
From: Barry Cooper <Barry_CooperspamKILLspamBC.SYMPATICO.CA>
To: .....PICLISTKILLspamspam.....MITVMA.MIT.EDU <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>
Date: Sunday, 7 June 1998 13:37
Subject: Re: VGA RGB REAL-TIME FRAME GRABBER


>>(You've probably remark my poor english...is't because
I'am a french
>>canadian!!!!)
>>
>
>  It's much better than my French!
>
>        Barry
>
Or my Canadian  :-) (or my French)

1998\06\08@141312 by Harrison Cooper

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face
               Sounds like you are trying to drive one of those color
sequential LCD displays (which I have driven).  Simply stated, these
require 3 fields of video, in the proper sequence of red, green the
blue, with the red sync being (remembering here) 3 times the length of
the other colors (this way the display can determine which field is
being displayed).  This is also composite video, so you will need to sum
the video with the sync signal.

               First off, you will need to separate out the three
colors of the video into three frame buffers.  I'd attempt to find a
commercial camera (like some of those on the market connecting to PC's
already ), that split it out.  Flash digitizing video is no simple
matter, so if you can find something that delivers that then you have
half of your headaches done with.  Now there are several different ways
to store it.....there are some line buffers for video or you can build a
FIFO from a FPGA (yes you can do this, I am presently....why is another
story...), but bottom line is you MUST store all three colors in
separate (or sequential memories...either way a FIFO).

               OK, so now you have all three colors from your frame
stored.  Now, generate a pixel clock, a sync circuit and something to
stream the data from the FIFO's (have to have a mux to select the source
as well).  Take the data thru your DAC of choice (careful of zero
crossover glitches), use a summing amp to generate the composite video,
amp for driving the display and you are done.  

               Personally, I think the  schedule for 10 weeks is pretty
aggressive, and the cost is something else.  Have to remember that
commercial devices that sell for $500 get this price thru aggressive
marketing and volume, and generally take quite a few units sold before
they even break even.

               Have fun!!

                               ----------
                               From:  Philibert Perusse
[SMTP:perussespamspam_OUTINO.QC.CA]
                               Sent:  Saturday, June 06, 1998 4:32 PM
                               To:  @spam@PICLISTKILLspamspamMITVMA.MIT.EDU
                               Subject:  VGA RGB REAL-TIME FRAME
GRABBER

                       Suppose this problem. You have to take an VGA
640x480 RGB signal where on
                       each color is mapped an grayscale image so we
have
                       three differents images comings at 60Hz...What
you have to do with this VGA
                       signal is to show it at 180Hz on a particular
monochrome LCD display. You
                       have to show the three monochrome images that
composed the VGA signal one
                       after the other. So lets look at
                       a solution of this problem.

                        I think that you must digitalize (GRAB) the 3
colors independently and
                       store them before to take them to the LCD one
color frame at the time. So,
                       this problem is almost the same than to make a
frame grabber that grab a VGA
                       signal and store it into any kind of memory (I
do prefer to use FIFOs).
                       Moreover, the complete design must take place
over a single 5"x4" board.
                       It's my solution but is someone has a better
idea!!!!

                       So, here is MY problem. Is-it realistic to do
this in 10 weeks (15 hours a
                       week) with a total cost (for each unit, not
considering the development) of
                       maximum 500$ by unit?

                       I think not! (Considering that Cypress 128k
FIFOs cost 150$ each) But I hope
                       I'm not wrong because I'll try to explain that
to my boss!!!

                       (You've probably remark my poor english...is't
because I'am a french
                       canadian!!!!)
       

                                           Phil!
                       Philibert PŽrusse <KILLspamperusseKILLspamspamino.qc.ca>
                       INO
                       369, rue Franquet
                       Sainte-Foy, ( QuŽbec) Canada  G1P 4N8
                       tel: (418) 657-7006 Fax: (418) 657-7009
                        http://www.ino.qc.ca

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