Real-time video capture and analysis

Dar Scott dsc at
Wed Jun 26 12:30:01 CDT 2002

On Tuesday, June 25, 2002, at 05:03 PM, Richard D. Miller wrote:

> First, is there a way to display video real-time within Rev (even 
> 10 fps
> will do)? And secondly, if so, would it be possible to draw on 
> those frames
> while they are coming into Rev? I'd probably be using a simple 
> live motion
> video camera like ZoomCam hooked up via USB or Firewire.

Is your need platform specific?  You might be able to create an 
external to do this.  An alternative is to write an application 
that sends frames via some IPC; I often use UDP for interprocess 
communication because I want the flexibility to put the processes 
on different computers.  This method also has the advantage in that 
the receiver can go up and down without interrupting the operation 
of the sender.

I have used DirectShow on Windows 2000 with the Osprey 2000.  If 
you go this route, there are a few ways you can go.  You can render 
the video in a tiny window.  You can find or make a filter that 
draws on the video.  I think this is only a partial solution to 
what you want.  The "sample grabber" filter allows you to get the 
stream values.  I derive a class from that to do what I want with 
samples.  An approach using the sample grabber might be what you 
want.  (The "sample grabber is not sample code; it is a filter that 
grabs media samples for applications.)

I have only begun to work with externals, though I have been 
successful in making a simple external.  One of the examples in the 
SDK (life) involves the manipulation of image data.  That may apply.

It is not clear to me what drawing on the frames mean?  If it were 
possible to put live images into an image, would a graphic object 
over that be what you want?  Or do you want to save frames in 
memory as they come in and modify them in real-time?

With the 10 fps requirement you will want to take care about speed 
at all levels and consider using only fast computers.

Hope this helps.

Dar Scott

Dar Scott
Dar Scott Consulting
dsc at

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Dar Scott Consulting provides software development services 
especially in distributed control systems on Windows 2000 and on 
small embedded computers.


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