Video for Windows and Capturing Rate

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2 total messages Started by axh96c Tue, 17 Mar 1998 00:00

#21

Author: axh96c
Date: Tue, 17 Mar 1998 00:00

33 lines
2120 bytes

Dear All,

I have successfully used the vfw32 and Avicap functions to capture frames
using a frame grabber card and a simple camera and perform image processing
tasks on the incoming frames. I have achieved this by using a Callback
function and capSetCallbackOnFrame macro. However, I am experiencing two
problems, namely

1) I can only capture 6 frames per second with the image processing functions
active or ( 8 fps without any image processing )

2) Every capture of a frame, makes the overlay (live) window fliker.
Therefore, with 6 fps there is alot of flikering!!

Question
--------

Is there a way to either moderately or significantly increase the fps of the
captures???? Is capSetCallbackOnVideoStream the route to take???? If so the
video buffer size cannot be constant and the capture time must be set???? Am I
right to think along those lines????

Also, is there a way to stop the flikering of the overlay window?

Any sort of help would be eagerly received.

Thankyou in advance.

axh96c@cs.nott.ac.uk

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Re: Video for Windows and Capturing Rate

#22

Author: Paul Jurczak
Date: Tue, 17 Mar 1998 00:00

31 lines
1995 bytes


axh96c@cs.nott.ac.uk wrote in message <6en05j$fk6$1@nnrp1.dejanews.com>...
>Dear All,
>
>I have successfully used the vfw32 and Avicap functions to capture frames
>using a frame grabber card and a simple camera and perform image processing
>tasks on the incoming frames. I have achieved this by using a Callback
>function and capSetCallbackOnFrame macro. However, I am experiencing two
>problems, namely
>
>1) I can only capture 6 frames per second with the image processing
functions
>active or ( 8 fps without any image processing )

I've run into similar problem with frame rate using VideoLab OCX (you can
download
free demo from their website). The best rate I could get was about 9 fps
(callback was
incrementing the counter only) grabbing 160x120 images and I know that my PC
can
easily do 30fps at 320x240 or more. My best explanation so far blames OCX
overhead,
but it looks less likely after reading about your problems. By the way, I
wasn't succesful
in using vfw32 directly - I was able to capture to file without preview
only. Could you
send me your code (only if its Borland C++ Builder)?

Paul Jurczak
<puplan@acm.org>

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