Apple Motion 5.1.1 User Manual
Page 173
Chapter 6
Create and manage projects
173
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 of these methods 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 a 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 like
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.
You can import audio clips with various sample rates and bit depths. When you do, Motion
resamples audio tracks to the sample rate and bit depth used by your computer. The default is
16-bit, 44.1 kHz float for the built-in audio interface. If you use a third-party audio interface, audio
is remixed to the sample rate and bit depth used by that device.
You can import audio files with sample rates up to 192 kHz and with bit depths up to 32 bits.
Mono and stereo files are supported. Multichannel audio files are also supported.
For more information about file formats Motion supports, see
File types supported by Motion
page 165. For more information on using audio in Motion, see
on page 1010.
A seamless way to browse for and import music from your iTunes library is to use the Music
category in the Motion Library. For more information, see
Add iTunes and iPhoto files from the
on page 183.
Note: You cannot import rights-managed AAC files, such as non-iTunes Plus tracks, purchased
from the iTunes Store.
Text files
Motion can read and work with a variety of text files, both as media elements and as text data to
incorporate in generators, particle systems, and replicator effects. For more information, see
on page 619.
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