Adobe 65021048 User Manual page 430

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:
Specifies the codec used to encode the video from those available on your system.
Codec
Specifies the encoding quality. Generally, higher values increase rendering time and file size.
Quality
Enables encoding of an alpha channel into the exported file for formats, such as Adobe Flash
Encode Alpha Channel
Video, that support alpha channels.
Conforms the output to the NTSC or PAL standard.
TV Standard
Scales the output frame's horizontal aspect to the specified width.
Frame Width
Scales the output frame's vertical aspect to the specified height.
Frame Height
The output frame rate for either NTSC or PAL formats.
Frame Rate
Specifies whether the output file's frames are interlaced, and if so, whether the upper or lower field is
Field Order
first in the scanning order.
Specifies the ratio of each pixel's width to height, which determines the number of pixels
Pixel Aspect Ratio
required to achieve a given image aspect ratio. Some formats use square pixels, while others use nonsquare pixels.
Specifies whether the codec achieves a constant or variable bitrate in the exported file:
Bitrate Encoding
•
Compresses each frame in the source video to the fixed limit you specify, producing a file
Constant Bit Rate (CBR)
with a fixed data rate. Therefore, frames containing more complex data are compressed more, while less complex
frames are compressed less.
•
Allows the exported file's data rate to vary within a range you specify. Because a given
Variable Bit Rate (VBR)
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.
Note: When comparing CBR and VBR files of the same content and file size, you can make the following generaliza-
tions: A CBR file may play back more reliably over a wider range of systems, because a fixed data rate is less demanding
on a media player and computer processor. However, a VBR file tends to have a higher image quality, because VBR
tailors the amount of compression to the image content.
Specifies the number of megabits per second of playback for the encoded file. (This setting is available only
Bitrate
if you select CBR as the Bitrate Encoding option.)
The following options appear only if you select VBR as the Bitrate Encoding option:
April 1, 2008
ADOBE PREMIERE PRO CS3 424
User Guide