I want to understand how ROI selection actually happens inside a camera? I have an ethernet camera, that can capture and send images to the PC, based on user defined ROI. The advantage of this is that I transfer only useful/relevant data from the image to my PC which will process it, instead of processing on the complete image.
The manufacturer has given a user guide, that gives very little details. The user guide says that ROI Selection-1(see figure below) is a valid ROI, and the ROI Selection-2 is of no use, in the sense that it will be still sending the complete image (though with some 0 values or garbage). That is the ROI selection-2 will not give any advantage of having only useful data transfer.
In support of his arguments he has given the following figure(without any explanation)
Can someone help me understand why the selection 2 is invalid. I am really facing problem in understanding these pulses. Is there any link giving details about these pulses?