Adobe After Effects CS4 - Manual (Page 726)

720 USING AFTER EFFECTS CS4
Rendering and exporting
Last updated 12/21/2009
• PCM (pulse-code modulation) Audio An uncompressed encoding format. Files of this format tend to be larger than
files of the other formats.
Audio Format The file format used for storing encoded audio data. Some audio formats support only uncompressed
audio, which has the highest quality, but uses more disk space. Some formats allow only one codec. Others allow you
to choose from a list of supported codecs.
Sample Rate or Frequency Choose a higher rate to increase the frequency at which audio is converted into discrete
digital values, or sampled. Higher sample rates increase audio quality and file size; lower sample rates decrease quality
and file size. However, setting the sample rate in the Export Settings dialog box higher than the sample rate of the audio
source doesn’t increase quality. Setting a sample rate different from the sample rate of the source file, requires
resampling, and additional processing time. You can avoid resampling by capturing audio at the same rate at which
you want to export it.
Channels or Output Channels Specify how many audio channels are in the exported file. If you choose fewer channels
than are in the master track of a sequence or project, Adobe Media Encoder downmixes the audio.
Sample Type Choose a higher bit depth to increase accuracy of audio samples. Higher bit depth can improve dynamic
range and reduce distortion, especially if you add additional processing, such as filtering or resampling. Higher bit
depths also increase processing time and file size; lower bit rates reduce processing time and file size. However, setting
the bit depth in the Export Settings dialog box higher than the bit depth of the source audio doesn’t increase quality.
Audio Interleave Specify how often audio information is inserted among the video frames in the exported file. See
your capture card documentation for the recommended setting. A value of one frame means that when a frame is
played back, the audio for the duration of that frame is loaded into RAM so that it can play until the next frame appears.
If the audio breaks up when playing, adjust the interleave value. Increasing the value lets the computer store longer
audio segments, and process them less often. However, higher interleave values require more RAM. Lowering the
value can make playback smoother. Most hard disks operate best with a 1/2-second to 1-second interleave value.
Setting the value to 0 disables Audio Interleave and speeds rendering time. Consider disabling Audio Interleave for
projects containing assets with large pixel dimensions.
Bitrate [kbps] Specifies the output bit rate of the audio. Generally, higher bit rates increase both quality and file size.
This option is available for AAC, mp3, and FLV.
Note: Options not documented here are specific to the selected format. For detailed information, consult the specifications
for the selected format.
Video export settings
In the Export Settings dialog box, the options available on the Video tab depend on the format you’ve specified. Video
settings include one or more of the following options. Video settings are listed under headings such as Video Codec,
Basic Video Settings, Advanced Settings, Bitrate Settings, Video Hinter Track Settings, and GOP Settings.
Note: Some capture card and plug-in software applications provide their own dialog boxes with specific options. If the
options you see are different from the options described here, see the documentation for your capture card or plug-in.
To save final rendering time:
• Use the same codec to capture and export.
• Render previews of your sequences as you make changes.
• Set the export quality setting to match the capture quality setting.
Video Codec or Codec Specifies the codec used to encode the video. The codecs available depend on the format you
choose.