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Setting Up the Stage for Video

Setting Up the Stage for Video

Let’s start with the basics. Open a new Flash document and then select Modify > Document (Control+J) to open the Document Properties dialog box (see Figure 1).

Document Properties dialog box

Figure 1. Document Properties dialog box

Here you determine the width and height of the Stage and its frame rate. But before you change anything, you need to decide what aspect ratio you are authoring to, so read on before you change anything.

NTSC (National Television Standards Commission), the video standard used in North America and most of South America, uses a 4:3 aspect ratio, which basically means a rectangular shape like a television set. To break it down in simpler terms, 4:3 means that for every four units wide, the picture is three units high. Apply this formula to a 16:9 screen and you’ll get 16 units of width for every nine units of height. Simple arithmetic so far, but it’s about to get tricky.

NTSC uses a pixel resolution of 720 x 480 pixels. But guess what? NTSC doesn’t use square pixels; they are rectangular. (Why do they have to make everything so complicated?) A problem arises when you develop content for video on your computer because you are creating square pixels to be displayed as rectangular pixels. That means your image will no longer have the correct aspect ratio and will look slightly stretched. To compensate for this pixel chaos, you need to adjust the width of the movie so that the pixel resolution is now 720 x 540. Panic is now over.

NTSC uses a frame rate of 29.97 or 30 frames per second (fps). You can export Flash movies that have different frame rates such as 12, 15, or 24 fps without worry. These frame rates will be converted to 30 by your video editing software, although a movie authored at 12 fps and converted to 30 fps will not look as smooth as a movie originally authored at 30 fps.

PAL (Phase Alternating Line), the predominant video standard outside the Americas, also has a 4:3 aspect ratio but uses a 720 x 576 pixel resolution and a frame rate of 25 fps. PAL has a greater resolution than NTSC and therefore has a better picture quality. Its higher color gamut level produces higher contrast levels as well. But the lower frame rate, compared to NTSC’s frame rate, will not be as smooth.

Film uses 24 fps, which is also a popular frame rate among animators. Although you can use 24 fps in your Flash project, when you export it to video you will need to convert the frame rate as well. This is easily done during the export process by specifying the appropriate frame rate for the video format to which you are authoring (PAL or NTSC). Keep in mind that this does not speed up your animation; rather, it simply makes your animation not appear as smooth. Because film and PAL have nearly the same frame rate (24 and 25, respectively), there will be hardly any visual difference.

Widescreen television, or HDTV, uses an aspect ratio of 16:9, which you can convert the same way by multiplying 16 and 9 by the same number. For example, 16 x 100 = 1600 and 9 x 100 = 900, for a total width and height of 1600 x 900 with which to author HDTV content. Depending on your display size and resolution, you may want to adjust the amount by which you multiply 16 and 9.

While resolution is important in video, Flash is resolution-free. As long as you are working in the correct aspect ratio, you can always resize your video when exporting. If you are using imported bitmaps in your Flash movie, you will want to use a width and height that exactly matches your final output to prevent the images from becoming scaled in Flash.

Back to Flash and your open Document Properties dialog box. Type in the width and height of your aspect ratio, enter the frame rate, and click OK.

Tip: If you are authoring several Flash movies that use the same properties, click the Make Default button before you click OK in the Document Properties dialog box. This ensures that every new Flash document you create will share these properties.