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Multi-Page PDF Files
You can import multipage PDF files. When you do, a parameter called Page Number
appears in the Properties Inspector when the PDF object is selected. Drag the slider to
set which page is displayed in the Canvas. Animate this parameter to display different
pages over time.
Important: Multilayered PDF files are not supported. To import a multilayered illustration,
export each layer as a separate PDF file and import these as a nested group of objects in
Motion.
More About Alpha Channels
Ordinary video clips and image files have three channels of color information: red, green,
and blue. Many video and image file formats also support an additional alpha channel,
which contains information defining areas of transparency. An alpha channel is a grayscale
channel where white represents areas of 100 percent opacity (solid), gray regions represent
translucent areas, and black represents 0 percent opacity (transparent).
When you import a QuickTime movie or an image file into a project, its alpha channel is
immediately recognized by Motion. The alpha channel is then used to composite that
object against other objects behind it in the Canvas.
There are two ways to embed alpha channel information into files. Motion attempts to
determine which method a media file uses:
• Straight: Straight alpha channels are kept separate from the red, green, and blue
channels of an image. Media files using straight alpha channels appear fine when used
in a composition, but they can look odd when viewed in another application. Translucent
effects such as volumetric lighting or lens flares in a computer-generated image can
appear distorted until the clip is used in a composition.
• Premultiplied: The transparency information is stored in the alpha channel as well as
in the visible red, green, and blue channels, which are multiplied with a background
color (generally black or white).
The only time it really matters which kind of alpha channel an object has is when Motion
doesn’t correctly identify it. If an media item’s alpha channel is set to Straight in the Media
list when it’s really premultiplied, the image can appear fringed with the premultiplied
color around its edges. If this happens, select the problematic item in the Media list, then
change its Alpha Type parameter in the Media Inspector.
Audio Files
You can import many audio file formats into your project, including WAV, AIFF, .cdda,
MP3, and AAC. Although Motion is not a full-featured audio editing and mixing
environment such as GarageBand or Logic Pro, you can import music clips, dialogue, and
sound effects. If you import a QuickTime file with mono or stereo tracks of audio, the
audio appears in the Audio Timeline.
226 Chapter 6 Creating and Managing Projects