Adobe After Effects CS3 - Manual (Page 619)

AFTER EFFECTS CS3
User Guide
614
After Effects and Adobe Premiere Pro add metadata to MPEG-2 files that Encore can read for aid in authoring and
building DVDs. This metadata contains information that enables Encore to multiplex audio and video, automati-
cally generate DVD chapter points, and open clips in the applications from which they were rendered. For more infor-
mation, see Encore Help.
Filter options for encoding
Noise, grain, and similar artifacts can interfere with the efficient compression of images. For this reason, the size of
the final output file may in some cases be reduced by applying a noise reduction filter to an image or movie before
compression takes place.
In the Export Settings dialog box, you can specify whether to apply a noise reduction filter before compression, and
you can also set the amount of noise filtering to apply.
If you intend to remove noise and grain from a project for reasons other than reduction of compressed file size,
consider using the Noise & Grain effects in Adobe Premiere Pro or After Effects.
Video options for encoding
In the Export Settings dialog box, the options available in the Video tab depend on the format you’ve specified. Video
settings include some or all of the following options:
Codec Specifies the codec used to encode the video from those available on your system.
Quality Specifies the encoding quality. Generally, higher values increase rendering time and file size.
Encode Alpha Channel Enables encoding of an alpha channel into the exported file for formats, such as Adobe Flash
Video, that support alpha channels.
TV Standard Conforms the output to the NTSC or PAL standard.
Frame Width Scales the output frame’s horizontal aspect to the specified width.
Frame Height Scales the output frame’s vertical aspect to the specified height.
Frame Rate The output frame rate for either NTSC or PAL formats.
Field Order Specifies whether the output file’s frames are interlaced, and if so, whether the upper or lower field is first
in the scanning order.
Pixel Aspect Ratio Specifies the ratio of each pixel’s width to height, which determines the number of pixels required
to achieve a given image aspect ratio. Some formats use square pixels, while others use nonsquare pixels.
Bitrate Encoding Specifies whether the codec achieves a constant or variable bitrate in the exported file:
• Constant Bit Rate (CBR) Compresses each frame in the source video to the fixed limit you specify, producing a file
with a fixed data rate. Therefore, frames containing more complex data are compressed more, while less complex
frames are compressed less.
• Variable Bit Rate (VBR) Allows the exported file’s data rate to vary within a range you specify. Because a given
amount of compression degrades the quality of a complex image more than it degrades the quality of a simple image,
VBR encoding compresses complex frames less and compresses simple frames more.
In general, an image is complex and more difficult to compress efficiently if it contains great detail or if it differs
significantly from previous frames, as it would in a scene containing motion.