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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
information from After Effects. See step 8.
5 Select a Quality level from Least to Best.
Note (Mac OS Only): If you intend to use key frames in the movie, hold down Option and
adjust the Quality slider to control the temporal compression of the movie. Temporal
compression compresses a movie by comparing successive frames and keeping only
changed data. High temporal quality maintains smoothness of motion. Low temporal
quality tends to produce jerkiness of motion because a pixel doesn't change unless the
difference between frames is great.
6 If you want the smallest possible files, and your compressor choice allows for a key
frame rate, select the box and type a number in the Key Frame Every box. Generally, you
should type a number equal to the frame rate. For example, if you set a frame rate of 30
fps, type 30 in the Key Frame box. This sets one key frame every 30 frames of your movie.
Note: If you are going to use the resulting movie in another After Effects composition, type
a small value (less than 5) in the Key Frame Every box or deselect the Key Frame Every
option. The presence of key frames greatly increases the memory required to edit and
render a movie.
7 Click OK.
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