this dialog allows you to select between "standard" (also called a square aspect ratio) and "ccir601" aspect ratio.

    the maximum resolution of the ccir601 mode is 720 pixels for both ntsc and pal. the standard/square aspect ratio mode has a maximum resolution of 640 pixels for ntsc and 768 pixels for pal.

    that since the sources are processed in a ccir601 format, the full 768 pixels of the standard/square aspect ratio mode of pal is not available. only 720 maximum pixels are available. if the standard/square aspect ratio mode is selected for pal, the osprey-210/220 drivers will limit the maximum resolution to only 720 pixels.