Real-time video capture and analysis
dsc at swcp.com
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 Consulting
dsc at swcp.com
Home, Lab & Office: +1 505 299 9497
Cell: +1 505 350 6953
8637 Horacio Place NE
Albuquerque, NM 87111
Dar Scott Consulting provides software development services
especially in distributed control systems on Windows 2000 and on
small embedded computers.
More information about the use-livecode