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Unregistered
January 5, 2007, 02:24:36
What is the recommended way to do scene detection is a video source?

I was thinking of using MV Delay and then comparing the two buffers.

In conjunction with this question, how can I "trigger" recording (or frame capture) using say Color Filter? For instance, everytime I detect a round, red ball, I want to capture a frame and save it.

Thank you in advance.

I really love your software and if I can solve these two issues, I am ready to buy!

Marc Cymontkowski
January 5, 2007, 09:29:48
Hi,

I was thinking of using MV Delay and then comparing the two buffers.

Yes, that's possible. Use MV Splitter to double the stream, then MV Delay on one of the streams and MV Absolute Difference to get the difference. If you connect the output to MV Mean, that will give you a 'difference value'.

This is a simple mechanism which works for a lot of cases. There is surely room to improve the scene detection.

In conjunction with this question, how can I "trigger" recording (or frame capture) using say Color Filter? For instance, everytime I detect a round, red ball, I want to capture a frame and save it.

If you use MV Image Grabber, you trigger the filter through the filters IMVTrigger interface. Our filters send events before and after a filters algorithm was actually applied. Usualy you use MV_ALGORITHM_END_EVENT to request the results from a filter. If the result is as desired, you would then trigger the grabber to capture an image.


Best Regards,

Marc Cymontkowski

dconnect
January 5, 2007, 14:01:29
Thank you for your quick response.

Regarding the trigger interface, is this exposed through the workbench?

In other words, how can I test this using the workbench? Or, is the only way to do this is through a programming interface?

Thank You,
Joachim

Marc Cymontkowski
January 5, 2007, 14:15:04
Hi Joachim,

On the MV Image Grabber filter, the trigger is available as I/O input pin or IMVTrigger interface. In the Workbench both can be used. Either by connecting the trigger input pin to a filter which provides a trigger output pin or through the trigger button on the peoperty page.

Since not every possible scenario can be implemented as I/O trigger output pin on all our filters, it often is only possible to do things in code.

E.g. in MV Blob Counters MV_ALGORITHM_END_EVENT (exposed by the Smart Controls filter events event), the blob counters interface is queried to check whether a certain type of blob was recognized (e.g. certain width/height/color/contour moment). Then the IMVTrigger interface of the MV Image Grabber is queried and a Trigger command is executed.

Several of our sample applications show how filter events are utilized for similiar tasks.


Best Regards,

Marc Cymontkowski