QuickTime 4 Reference

Improved Support for Digitizing Video in Windows

Before QuickTime 2.1, an application displaying the output of a sequence grabber video channel in a window would have to pause the sequence grabber before moving or resizing a window, before a menu was pulled down, or whenever the application was put into the background. If an application failed to take these precautions, it was possible for the digitized video to draw outside the window with which it was associated.

QuickTime 2.1 solves these problems so that an application using a sequence grabber video channel in a window no longer has to take any special precautions to ensure that the video remains within the window. As long as the application calls SGIdle regularly, the sequence grabber automatically takes care of pausing and unpausing the video as necessary.