User Guide

CHAPTER 12
370
Rendering a Movie
Choosing compression options
Compression is essential to reduce the data size of movies that would otherwise be so large
as to prohibit effective playback. When compressing a movie file, you can fine-tune it for
the best-quality playback on a computer, on a video playback device, on the Web, or from
a CD-ROM drive.
QuickTime and Video for Windows have several built-in, software-based compression
algorithms. For a list of QuickTime compressors, see the Adobe Web site.
Setting QuickTime compression options
Choices you make in the Compression Settings dialog box require trade-offs between file
size and movie quality. The higher the visual quality of your movie, the larger the file size.
Quality The Quality control specifies the spatial compression of the movie, which
compresses the data in each frame of a composition. Higher quality produces better image
quality but results in a bigger movie file. Lower quality results in a blocky and slightly
blurred image (although it is still recognizable) and a smaller, more compressed movie file.
Note that this quality is unrelated to each layer’s quality setting in After Effects.
Key Frame Every In QuickTime terminology, the term key frames is different from the
change-over-time keyframes placed in the After Effects Timeline window. In QuickTime,
key frames are frames that occur at regular intervals in the movie. During compression
they are stored as complete frames. Each intermediate frame that separates them is
compared to the previous frame, and only changed data is stored. This greatly reduces
movie size. Shorter intervals between key frames enable faster seeking and reverse
playback but can significantly increase the size of the file.
To specify QuickTime compression settings:
1 In the Render Queue window, click the underlined name of the output module.
2 For Format, choose QuickTime.
3 Click Format Options in the Video Output section.
4 In the Compression Settings dialog box, choose a compressor from the first menu in the
Compressor section.
Note: Set the color depth in the Compression Settings dialog box instead of in the Output
Module Settings dialog box. This ensures that non-Adobe plug-ins receive color depth infor-
mation from After Effects. See step 8.
UG.book Page 370 Wednesday, February 21, 2001 12:05 PM