When a message box has a comma in it, the message is separated into two distinct messages. In this case, the message (loopset $1 $2, $1) does two things. Sending a loopset message sets the start and end points of the loop. Sending just an integer value tells imovie where to start playback. So, in this case, the two messages are combined for efficiency and tell the imovie object to set its loop points to $1 and $2 and then start playback at the $1 point.

For your second question, the two scale objects are being used to scale the dimensions of your monitor (from screensize) to match the dimensions of the imovie object. Thus as you move your mouse around your monitor the info from mousestate is scaled so that the video image stays within the box.

Thank you very much BKSHEPARD.

So regarding my first question, the tutorial patch tries to show one useful way to set the starting point, even though it does not change any result in this specific patch. Is my understanding correct?

About my second question, I think I misunderstood what the first and second augments of 'rect' message do. I was wrong that I thought it only set the upper-left location of a rectangle. Here is the sentence I found in the relevant reference file. 'The first two numbers specify the position of the rectangle within the movie window, in relative coordinates' Could anyone kindly tell me how 'relative coordinates' work? For me, it seems when the rectangle is closer to the upper-left corner of the imovie object, the augments set the upper-left corner of the rectangle, and when the rectangle is closer to the bottom-right corner of the imovie object, the augments are used to set the bottom-right corner of the rectangle.

The $1 is the x coordinate of your given computer screen, $2 is the y coordinate of your screen. So the upper-left corner pixel has the values $1 = 0 and $2 = 0, the bottom-right corner pixel the values $1 = 1 and $2 = 1. In the case your monitor has the size x= 1920 per y = 1080 pixels, as the $1 and $2 are scaled values relative to the (your) screen X/Y values, the upper-left pixel values, $1 = 0 and $2 = 0, are equivalent to x = 0, y = 0; but the bottom-right values $1 = 1 correspond to, e.g. x = 1920, and $2 = 1, to y = 1080. Try to slide on the left margin of your monitor screen down, $1 will stay zero, meanwhile $2 will go towards 1. (=> y = 1080). by doing so this will become clear for you. By the way, for me this is a basic but efficient exemple to explain motion capture and the conditionning of a flux of data to relative values. Best, Helmuth

Thank you very much Helmuth.

By the way, with this patch, when I move my pointer to the bottom-right of Mac's screen, the numbers become '1.001' and '1.0011', rather than '1' and '1', which is strange.