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'[OT] Combined video and bi-directional data transm'
1998\06\09@142417 by Douglas Reid

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This is off-topic but will no doubt involve a PIC!

Does anyone have any ideas for the chip-set/ approach to use for the
following project:

It is required to transmit a video picture with associated data signals
(serial, RS232, etc.) for camera control down the same media.  Ideally, the
solution should support the alternatives of twisted pair wiring, coaxial
cable or fibre-optics.

The application is for a CCTV security system in which the picture is
transmitted from a camera which is controlled over the same link.
Bi-directional transmission of control data is required so that, for
example, both the camera can be moved and data received back (feedback data
of camera position, alarm inputs, etc.).  Video only needs to be transmitted
in one direction over the link.

I imagine that a standard DSP could be programmed to meet this requirement.
Perhaps use of video-conferencing or multi-media chip-sets would avoid
"re-inventing the wheel" by handling digitisation, data compression, etc.?

Harris multi-media chips support VBI data closed captioning whereby teletext
type data can be recovered.  This may provide one strategy?  How could I
combine the data with the video information in the first place?  How can
bi-directional data transmission be implemented?

An analogue approach may be possible in which the control data is
transmitted during the part of the picture frame transmission in which there
is no image data.  However, this analogue solution would be somewhat
susceptible to interference effects.

Honeywell offer optical duplexers which enable a single optical fibre to be
used bi-directionally.  However this is a somewhat expensive component.  Are
there any cheaper alternatives?

I should much appreciate any ideas as to the best way to tackle this project.

I would also consider contracting out this design project if anyone is
interested?

Any help would be much appreciated!
Thanks,

Doug Reid
Liverpool, England

1998\06\09@155031 by ogerio Odriozola

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Try http://www.forceinc.com to get an idea. They have all sorts of fibre optic tx
and rx with video, audio, data, etc.

Rogerio





spam_OUTDouglas.ReidTakeThisOuTspamBTINTERNET.COM on 09/06/98 01:41:20 PM

Please respond to .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU

To:   PICLISTspamKILLspamMITVMA.MIT.EDU
cc:    (bcc: Rogerio Odriozola/MTY/TVA/Dataflux)
Subject:  [OT] Combined video and bi-directional data transmission




This is off-topic but will no doubt involve a PIC!
Does anyone have any ideas for the chip-set/ approach to use for the
following project:
It is required to transmit a video picture with associated data signals
(serial, RS232, etc.) for camera control down the same media.  Ideally, the
solution should support the alternatives of twisted pair wiring, coaxial
cable or fibre-optics.
The application is for a CCTV security system in which the picture is
transmitted from a camera which is controlled over the same link.
Bi-directional transmission of control data is required so that, for
example, both the camera can be moved and data received back (feedback data
of camera position, alarm inputs, etc.).  Video only needs to be
transmitted
in one direction over the link.
I imagine that a standard DSP could be programmed to meet this requirement.
Perhaps use of video-conferencing or multi-media chip-sets would avoid
"re-inventing the wheel" by handling digitisation, data compression, etc.?
Harris multi-media chips support VBI data closed captioning whereby
teletext
type data can be recovered.  This may provide one strategy?  How could I
combine the data with the video information in the first place?  How can
bi-directional data transmission be implemented?
An analogue approach may be possible in which the control data is
transmitted during the part of the picture frame transmission in which
there
is no image data.  However, this analogue solution would be somewhat
susceptible to interference effects.
Honeywell offer optical duplexers which enable a single optical fibre to be
used bi-directionally.  However this is a somewhat expensive component.
Are
there any cheaper alternatives?
I should much appreciate any ideas as to the best way to tackle this
project.
I would also consider contracting out this design project if anyone is
interested?
Any help would be much appreciated!
Thanks,
Doug Reid
Liverpool, England

1998\06\09@184731 by Andy Kunz

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At 06:41 PM 6/9/98 +0000, you wrote:
>This is off-topic but will no doubt involve a PIC!
>
>Does anyone have any ideas for the chip-set/ approach to use for the
>following project:
>
>It is required to transmit a video picture with associated data signals
>(serial, RS232, etc.) for camera control down the same media.  Ideally, the
>solution should support the alternatives of twisted pair wiring, coaxial
>cable or fibre-optics.

Modulate the output of the TV camera (ie, make a mini TV station).  You can
buy cheap Channel 3 modulators like the ones that used to come with video
games for almost nothing.

Put an RF transceiver on the same line using a splitter (connected backwards).

Create an RF transceiver for the command data.  This goes at the
controlling end.  The two directions for data use different frequencies.

Data going from the controller to the camera is in the "forward" direction.
Data responses (not video) from the camera to the controller is the
"return" direction.

If you want an existing system which can be easily adapted, contact me
private and I'll give you his e-mail.

Andy

==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\06\10@120629 by Chris Eddy

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Andy has a fine idea.. (never a dissapointment from Andy)..  It would be
relatively easy with off the shelf junk.

If you must live in the video level world, though, I can picture (no pun
intended) something where you pass the data back and forth in the vertical
blanking interval.  This area is the classic location to put data, but is usuall
y
implemented with data in one direction (from cable supplier to customer).  If yo
u
are video electronics savvy, you could craft a bi-directional data management
system.  A simple protocol would have to be established, such that either end ca
n
know when it's turn has come (The MAC layer so to speak).  The one difficulty
that I see is solving the case where fiber optics is used.  Unless you have two
fibers, in which it becomes easier yet.  But not compatible with the other two
copper media.

G'luck.
Chris Eddy, PE
Pioneer Microsystems, Inc.

Douglas Reid wrote:

{Quote hidden}

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