Example: 74 * 640 400 => * 20 * * The option viewport specifies a crop rectangle to apply to the Amiga video-out. The default, if not specified, is to calculate this automatically (auto-scaling). To force an uncropped viewport (and effectively disable autoscaling), you can specify: viewport = * * * * => 0 0 752 574 If auto-scaling does not work perfectly for a game, and you want a cropped output, you can specify any crop rectangle (x y width height), The following viewport is appropriate for many games: viewport = * * * * => 74 36 640 400 Often, Amiga games have viewports with varying size and position. The default auto-scaling system works well with many games, but not all. You can modify the auto-scaling algorithm by specifying patterns to replace. The viewport setting will be consulted each time the auto-scaling algorithm chooses a new viewport. Here are some examples: The following viewport pattern will match if the auto-scaling algorithm thinks the viewport should be 640×400 and start at 74 from the left. The top can be anything (*). Now, the top parameter will be forced to 20. A * on the right side of => means to keep the existing value, while a * on the left side means to match any value. viewport = 74 * 640 400 => * 20 * * The following viewport specification does nothing: * * * * => * * * * This following viewport is a simple translation (74 40 640 400 => * 36 * * would behave the same): 74 40 640 400 => 74 36 640 400 You can specify more than one pattern by separating them with commas. In this case, the first matching pattern will be used. Here is a viewport specification which works perfectly with Pinball Dreams: (this basically says: keep the viewport 74 28 640 524 as it is, and all other viewports will be forced to 74 36 640 512. viewport = 74 28 640 524 => * * * *, * * * * => 74 36 640 512 This one is great for Turrican II: viewport = 74 * 640 384 => 74 36 640 424 But rembember, many games work perfectly with the builtin viewport detection, and if you do not want auto-scaling, you can disable it by specifying a fixed viewport of your choice.