Some advice on video frame grabbing

[Doug Lerner]

On 1/31/04 5:57 PM, "Chipp Walters" <chipp at chipp.com> wrote:

> Doug,
> 
> I haven't used video frame grabbing, but I might suggest some things to
> look at:
> 
> When you call:
> revVideoFrameImage userImageWidth, userImageHeight, "videoimagedata"
> 
> you might want to include before it:
> 
> set the defaultStack to "theStackWithTheVideo"

You mean the stack with the video grabber window in it?

> 
> (I assume it is not a palette, if it is, it might NOT work at all)

It's not a palette.

> 
> Also, see if you can do it all on the same stack as a test (just like
> the example). If it does work, then you can isolate your frontmost
> stack issues from there.

Well, as a test I can do that in the sample stack. It would be hard to do as
a test in my current app now considering how complicated it has gotten.

But weirdest of all - it worked one time! But I couldn't repeat it after
that. 

Also, sometimes the revCloseVideoGrabber that I call when I close the video
grabber window (in closeStack) does not seem to get sent and I need to
invoke it manually.

Thanks,

doug

> 
> hope you get it working,
> Chipp
> 
> 
> 
> On Jan 31, 2004, at 2:38 AM, Doug Lerner wrote:
> 
>> I have a question for you experts.
>> 
>> I basically copied scripts from the sample video stack (where this
>> works
>> correctly), and most of it seems to be working in my stack. But when I
>> try
>> to grab a frame from the video grabber window it does not display in
>> the
>> target image after I use the "set imageData" command.
>> 
>> Without boring you with all my code, this is the snippet that grabs the
>> frame and sets the imageData:
>> 
>> put empty into videoimagedata
>> 
>> put the width of image "userPortrait" of stack portraitName into
>> userImageWidth
>> 
>> put the height of image "userPortrait" of stack portraitName into
>> userImageHeight
>> 
>> revVideoFrameImage userImageWidth, userImageHeight, "videoimagedata"
>> 
>> set the imageData of image "userPortrait" of stack portraitName to
>> videoimagedata
>> 
>> 
>> Seems vanilla enough, right? The only thing I am doing different from
>> the
>> sample scripts is that my target image happens to be in another stack.
>> 
>> All the stacks/windows are open and everything has the correct height
>> and
>> width set.
>> 
>> If I log userImageWidth, userImageHeight and the captured
>> videoimagedata,
>> there are what seem to be correct values in all of them. Well, the
>> height
>> and width anyway seem correct. I can't visually confirm that the value
>> of
>> videoimagedata is correct, but it is the correct size - userImageWidth
>> x
>> userImageHeight x 4.
>> 
>> If I "put image userPortrait" there is what appears to be PNG data in
>> there.
>> 
>> If I check the "number of characters of the imageData of image
>> userPortrait"
>> there is the correct 57,600 characters in there (the image is 120x120).
>> 
>> And the paintCompression of image userPortrait is "png" in my stack
>> and also
>> in the sample stack.
>> 
>> But:
>> 
>> * No image is displayed (even though it is displayed in the video
>> grabber
>> window of course)
>> 
>> * If I "put the imageData of image userPortrait" the value displayed
>> looks
>> empty in the message box - not even garbage characters.
>> 
>> Any ideas?
>> 
>> Thanks!
>> 
>> doug
>> 
>> 
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> 
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