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PICList Thread
'Video overlay for PIC?'
1997\03\05@022418 by Jeff King

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Not quite a direct PIC question, but wondered if anyone had
interfaced any device(s) to generate a video text overlay
over either NTSC or PAL video? I believe Philips has some
IC2 devices to do this, but wondered if there was any "real
world" experince on this list?

Specificially, I'm just looking to display simple text (doesn't
need to be anti-aliased) over top of video. Of course, it would
need to be in sync with the underlying video signal.

Thanks

Regards,

------------------------------------
| Jeff King      Aero Data Systems |
| spam_OUTjeffTakeThisOuTspammich.com  P.O. Box 510895   |
| (810)471-1787  Livonia, MI 48151 |
|F(810)471-0279  United States     |
------------------------------------

1997\03\05@024720 by David BALDWIN

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Jeff King wrote:
{Quote hidden}

       I already saw a project like this, I think its on David Taits pic stuff
page. I was a clock that displayed time on the TV screen. Hope this
helps.
--

 _____________
 \           /               David BALDWIN
  \ ALCATEL /               Design engineer
   \TELECOM/
    \     /         SdM (Societe de Microelectronique)
     \   /
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1997\03\05@025753 by Mike

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> I was a clock that displayed time on the TV screen.

You mean there was a video of you with your hands in various positions
showing the hands of a clock ?

(Sorry couldn't resist it :)))

Rgds

Mike

Some say there is no magic but, all things begin with thought then it becomes
academic, then some poor slob works out a practical way to implement all that
theory, this is called Engineering - for most people another form of magic.
                                                                      Massen

1997\03\05@042421 by David BALDWIN

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Mike wrote:
>
> > I was a clock that displayed time on the TV screen.
>
> You mean there was a video of you with your hands in various positions
> showing the hands of a clock ?
>
> (Sorry couldn't resist it :)))
>
> Rgds
>
> Mike
>
> Some say there is no magic but, all things begin with thought then it becomes
> academic, then some poor slob works out a practical way to implement all that
> theory, this is called Engineering - for most people another form of magic.
>                                                                        Massen


       Not bad, not bad.... :)
--

 _____________
 \           /               David BALDWIN
  \ ALCATEL /               Design engineer
   \TELECOM/
    \     /         SdM (Societe de Microelectronique)
     \   /
      \ /      B.P. 4205            Phone : +32 (0)71 442932
       V       B-6000 Charleroi     Fax   : +32 (0)71 442905
               (Belgium)            .....baldwinKILLspamspam.....etca.alcatel.be

1997\03\05@081343 by Byron A Jeff

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>
> Not quite a direct PIC question, but wondered if anyone had
> interfaced any device(s) to generate a video text overlay
> over either NTSC or PAL video? I believe Philips has some
> IC2 devices to do this, but wondered if there was any "real
> world" experince on this list?
>
> Specificially, I'm just looking to display simple text (doesn't
> need to be anti-aliased) over top of video. Of course, it would
> need to be in sync with the underlying video signal.

Go take a read around the http://www.circellar.com web site. There was a design
contest winner that had a wind speed indicator with video output that used
a single PIC. It probably could be adapted to your overlay project with
the use of a sync detector. In a nutshell:

1) Use the sync detector to detect starts of frames and lines.
2) Use a analog switch that will pass either the regular video or
  pure white.
3) Program the PIC to switch the switch at appropriate times.

I've never done this, as I'm not a video guy, but I think the basic
concept is sound.

Hope this helps,

BAJ

1997\03\05@091843 by Andy Kunz

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>1) Use the sync detector to detect starts of frames and lines.
>2) Use a analog switch that will pass either the regular video or
>   pure white.
>3) Program the PIC to switch the switch at appropriate times.
>
>I've never done this, as I'm not a video guy, but I think the basic
>concept is sound.

I've done this.  One more point:

4)  Run the PIC synchronous to the horizontal clock rate.

Andy
======================================================================
Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865 USA
             Electronics for Industry & R/C Hobbyists
        "Go fast, turn right, and keep the wet side down!"
======================================================================

1997\03\05@093648 by David BALDWIN

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If the goal is to write something on the screen, why do you need syncro
detection, and so on? Why don't you do things easyer?

1997\03\05@113625 by Jeff King

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Hi:

My PIC will be doing other things, so I'd like it to be off
board. Overlay (i.e. being able to insert text into a pre-
existing video signal) is a requirement.

The 'chips' I am refering to are in many (most) TV's today...
the type that can overlay closed captioning or various TV
functions (like your volume setting and channel). All
the various functions (sync seperation etc) are already
done for you. Generally you talk to them via a IC2 line.

What I am asking is if anyone has used any of these with
PIC's and what there experince's were. As this is not
a specific PIC question, I might be best asking this on
sci.electronics. But since my target processor is a PIC,
I thought I'd start here :-)

Thanks!

Regards,

------------------------------------
| Jeff King      Aero Data Systems |
| EraseMEjeffspam_OUTspamTakeThisOuTmich.com  P.O. Box 510895   |
| (810)471-1787  Livonia, MI 48151 |
|F(810)471-0279  United States     |
------------------------------------

1997\03\05@145949 by Richard Katezansky

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I've used several types of OSD (on screen display) chips in the past. For a
while the most common types were Fujitsu MB88323 ,88325 and Mitsubishi
M50554 ect.  I still have documentation for these types and probably have
some parts floating around.  These are fairly easy devices to use and have
SPI interfacing to a micro.
They offer up to 12 lines of 24 character text.  Overlay is possible in
monochrome.

If you want to discuss it more send me some e-mail directly.

Regards.




At 11:25 AM 3/5/97 -0500, you wrote:
{Quote hidden}

******************************
Richard Katezansky
Tangent Electronics Ltd.
Montreal, Canada
******************************

1997\03\05@171826 by Eric Smith

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Jeff King <@spam@jeffKILLspamspamMICH.COM> wrote:

> Not quite a direct PIC question, but wondered if anyone had
> interfaced any device(s) to generate a video text overlay
> over either NTSC or PAL video? I believe Philips has some
> IC2 devices to do this, but wondered if there was any "real
> world" experince on this list?
>
> Specificially, I'm just looking to display simple text (doesn't
> need to be anti-aliased) over top of video. Of course, it would
> need to be in sync with the underlying video signal.

Byron A Jeff <KILLspambyronKILLspamspamCC.GATECH.EDU> replied:

> Go take a read around the http://www.circellar.com web site. There was a design
> contest winner that had a wind speed indicator with video output that used
> a single PIC. It probably could be adapted to your overlay project with
> the use of a sync detector. In a nutshell:
>
> 1) Use the sync detector to detect starts of frames and lines.
> 2) Use a analog switch that will pass either the regular video or
>    pure white.
> 3) Program the PIC to switch the switch at appropriate times.

What you will find is that there is an unacceptable amount of jitter in
the horizontal positioning of your overlaid video.  Generally the tightest
synchronization you can get to the horizontal sync will be two PIC
instructions, or perhaps one instruction using some hardware-dependent
tricks.  If the PIC is running at 20 MHz, that's 200 or 400 nS.

If you really want to use a PIC to generate a video overlay, you need to
use a PLL to generate a master clock for the PIC that is a phase-locked
multiple of the horizontal sync.

In general it is much easier to use the video overlay chips that are designed
for this purpose.  Also, they can generate better looking characters; the
PIC can't provide very good horizontal resolution.

But for specialized applications, using the PIC and PLL approach may be
useful.  That's how my closed-caption *encoder* works.

Cheers,
Eric

1997\03\06@020436 by nigelg

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In message  <RemoveME2.2.32.19970305162557.006ab3b0TakeThisOuTspammail.mich.com>> spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU writes:

Hi,

> My PIC will be doing other things, so I'd like it to be off
> board. Overlay (i.e. being able to insert text into a pre-
> existing video signal) is a requirement.
>
> The 'chips' I am refering to are in many (most) TV's today...
> the type that can overlay closed captioning or various TV
> functions (like your volume setting and channel). All
> the various functions (sync seperation etc) are already
> done for you. Generally you talk to them via a IC2 line.

This requirement disposes of most of the TV chips used for OSD, they
normally produce an RGB signal that is fed directly to the CRT cathode
drivers. They are not able to add text to a comnposite video signal.

The type of chip you require is that used for OSD in VCR's and satellite
receivers, they genlock text on top of an existing composite video signal.

> What I am asking is if anyone has used any of these with
> PIC's and what there experince's were. As this is not
> a specific PIC question, I might be best asking this on
> sci.electronics. But since my target processor is a PIC,
> I thought I'd start here :-)

The main problem is finding data sheets for the video chips, I tried to
find them for chips from Sharp, Mitsubishi and NEC. The only datasheet I
was able to obtain was from NEC for the uPD6450, this will display 12x24
characters on top of an existing composite signal. In the UK it is used in
a number of Hitachi VCR's and Amstrad satellite receivers.

I currently have PIC (16C84) code for controlling the uPD6450, it can
either superimpose text over a composite signal, or display on a coloured
background - this is usually used in VCR's when there is no signal
available, most often defaults to a 'blue mute' screen provided by the
display chip.

If you would like the code, feel free to ask, although It's not finished
yet, it does feed the display chip quite nicely!.

Nigel.

       /--------------------------------------------------------------\
       | Nigel Goodwin   | Internet : TakeThisOuTnigelgEraseMEspamspam_OUTlpilsley.demon.co.uk     |
       | Lower Pilsley   | Web Page : http://www.lpilsley.demon.co.uk |
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       | England         |                                            |
       \--------------------------------------------------------------/

1997\03\06@030756 by Gvran Mvrk

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Jeff King wrote:

 Hi:

 My PIC will be doing other things, so I'd like it to be off
 board. Overlay (i.e. being able to insert text into a pre-
 existing video signal) is a requirement.

 The 'chips' I am refering to are in many (most) TV's today...
 the type that can overlay closed captioning or various TV
 functions (like your volume setting and channel). All
 the various functions (sync seperation etc) are already
 done for you. Generally you talk to them via a IC2 line.

 What I am asking is if anyone has used any of these with
 PIC's and what there experince's were. As this is not
 a specific PIC question, I might be best asking this on
 sci.electronics. But since my target processor is a PIC,
 I thought I'd start here :-)

 Thanks!

 Regards,

 ------------------------------------
 | Jeff King      Aero Data Systems |
 | RemoveMEjeffspamTakeThisOuTmich.com  P.O. Box 510895   |
 | (810)471-1787  Livonia, MI 48151 |
 |F(810)471-0279  United States     |
 ------------------------------------

Take a look at the uPD6450 family from NEC. They have a simple 3-wire
interface, very easy to handle in SW. Sync separation has to be made
separately though. LM1881 is the basic choice.
Goeran Moerk
gmEraseMEspam.....sysinno.se

1997\03\09@203606 by Dieter Macke

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Hi Jeff,

Jeff King schrieb an Dm:

JK> The 'chips' I am refering to are in many (most) TV's today...
JK> done for you. Generally you talk to them via a IC2 line.

What are these chips and can they display (changeable) text in various
positions of the tv-screen (pal) ?

cu Dieter
... Mama, 's Guido packt aus!

1997\03\10@102403 by Zemin Liu

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>Hi Jeff,
>
>Jeff King schrieb an Dm:
>
> JK> The 'chips' I am refering to are in many (most) TV's today...
> JK> done for you. Generally you talk to them via a IC2 line.
>
>What are these chips and can they display (changeable) text in various
>positions of the tv-screen (pal) ?
>
>cu Dieter
>... Mama, 's Guido packt aus!
>
>

I know one of these chips is TC9020P (should be Toshiba's product). I have its
diagram but don't know how to program it. Actually I am searching for the
necessary infomation to use it. Does any one know?

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