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'[OT] Video signals'
1999\09\12@034608 by Justin Grimm

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Hi Piclisters
A couple of questions about video signals-

How does a normal cmos minature camera output it's data,
I think its serially in time but analog in it's amplitude? Am I right?
If so then how does this transmit the image?

Does anyone know of any links for this info.

How would I send the video signal over a rs232 link?

Thanks
Justin

1999\09\13@071725 by Caisson

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> Van: Justin Grimm <spam_OUTeclipseTakeThisOuTspamCOASTLINK.COM.AU>
> Aan: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
> Onderwerp: [OT] Video signals
> Datum: zondag 12 september 1999 10:06
>
> Hi Piclisters
> A couple of questions about video signals-
>
> How does a normal cmos minature camera output it's data,
> I think its serially in time but analog in it's amplitude? Am I right?
> If so then how does this transmit the image?

It's send as a standard Video-signal.  Like the Video signals going in and
coming out of your TV (*not* the Antenna-signal, but the SCART !).  It's 1
volt top-top. with the lower 1/3 reserved for sync-signals (line & frame),
and the upper 2/3 for the analogue image-data.

Color is introduced as signals that are "early", "on time" and "too late"
in phase , in reference to a "color-burst" signal supplied just after every
line-sync pulse.

The above color-coding goes for PAL signals (european coding) ...

In short, you can (mostly) connect it directly to your TV or Video.

> Does anyone know of any links for this info.

Try searching for "video signals" or the definitions for different methods
to code a Video-signal, like  "PAL" and  "NTSC"

> How would I send the video signal over a rs232 link?

I would not know, but if you would want to send the "Raw" data , you would
need a *fast* connection ...

Greetz,
 Rudy Wieser

1999\09\13@181154 by kayode.ayandokun

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Justin,

For good data sheets on CMOS camera modules visit http://www.vvl.co.uk.
There are several which describe the composite video signal format.

Kayode

1999\09\13@210227 by Gennette Bruce

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       <snip>
>  > How does a normal cmos minature camera output it's data,
> > I think its serially in time but analog in it's amplitude? Am I right?
> > If so then how does this transmit the image?
>
> It's send as a standard Video-signal.  Like the Video signals going in and
> coming out of your TV (*not* the Antenna-signal, but the SCART !).  It's 1
> volt top-top. with the lower 1/3 reserved for sync-signals (line & frame),
> and the upper 2/3 for the analogue image-data.
>
> Color is introduced as signals that are "early", "on time" and "too late"
> in phase , in reference to a "color-burst" signal supplied just after
> every
> line-sync pulse.
>
> The above color-coding goes for PAL signals (european coding) ...
>
> In short, you can (mostly) connect it directly to your TV or Video.
       <snip>

       There may be a complication in certain cameras designed for 'home'
use - experts please feel free to expond -

       Just a note on PAL signals, I'm not exactly sure, but I think the
phase shifting that encodes the colour information is left alone in studio
and closed circuit installations, *but* is reversed on each successive line
when the signal is broadcast (Phase, Alternating, Line = PAL). Receivers
also invert the colour signal phase on each alternating line too.

       This refinement was added to later colour implementations to 'cancel
out' phase shift errors introduced by reflection and refraction of the
broadcast signal as it bounces off hills and buildings. The receiving set
actually creates the sum of each 2 successive lines and shows that on the
screen. [The picture difference between any 2 successive lines is assumed to
be negligible, after all an interlaced display is showing the 'same' line a
frame apart (1/50 sec, or 1/60 sec in USA)]

       e.g. line 252 is mixed with a re-inverted (colour phase inverted and
delayed copy of) line 251 and shown on the screen as line 252, then the
inverted (colour phase inverted and delayed copy of) line 252 is mixed with
line 253 for the next line to show. Any phase errors in the received signal
will be shifting the colour information in the same direction, so that the
summed information gives 2* the colour signal with errors cancelling out -
       (colour signal + error) + (-1 * (-colour signal + error)) = 2 *
colour signal

       The sets are designed to use the 2* strength colour signals.
       The original delay technique was to use a transducer to change the
electrical signal into high frequency sound that passed through a (carefully
chosen) length of glass before being converted back to an electrical signal.
The delay was one TV line so these devices were called delay lines. Modern
ones are all electronic.

       So, back to the start, some cameras *MAY* be doing PAL and some
*MAY* not, so if you want to process this signal you need to know more about
it - experts please tell us what is going on in modern cmos & CCD cameras -
please.

       Bye.

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