Apple Final Cut Pro 6 - Manual (Page 1419)

634 Part IV Real Time and Rendering
 Memory bus speed: Computers with a faster memory bus allow better real-time
performance because data can be sent more quickly between RAM and the
computer processor.
 Hard disk speed: The faster your hard disk can read data, the more video data
Final Cut Pro can access in real time. With some video formats, such as
uncompressed video, hard disks may not be able to keep up with the video data rate,
making real-time playback impossible. Multiclips and multiple video layers require
many video streams to play back simultaneously. A faster hard disk allows more
streams to play back simultaneously in real time.
 Codec: Not all codecs are supported by RT Extreme, but the most commonly used
ones are. Some codecs require more processing power and RAM to play back than
others. For example, the long-GOP MPEG-2 compression used by HDV requires more
RAM and processing power to decompress than I-frame-only codecs such as DV. For
more information, see “
Supported Real-Time Playback Codecs ” on page 638.
 External video monitoring: Enabling output via FireWire or other video interfaces
requires additional processing power and may limit the number of effects you can
play back in real time. For more information, see Volume I, Chapter 14, “External
Video Monitoring.”
Real-Time Audio Mixing in Final Cut Pro
Final Cut Pro can mix and play back multiple audio tracks in a sequence in real time,
even while you make adjustments to levels, stereo pan, and audio filters. The number
of tracks that can be played back depends on the number of filters applied to your clips
and your computer’s capabilities and settings, including:
 Your computer’s processor speed
 The seek time and sustained transfer rate of your hard disk
 The amount of RAM available to Final Cut Pro
 The Audio Playback Quality setting in the General tab of the User Preferences window
Note: For information on this setting, see Volume IV, Chapter 23, “Choosing Settings
and Preferences.”
Different filters and transitions affect real-time playback to varying degrees. If
Final Cut Pro can’t mix all the tracks in a sequence in real time, you hear a series of
beeps indicating that part or all of your sequence must be rendered before being
output as a final mix.
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Tip: You can turn these beeps off by deselecting the Beep When Playing Unrendered
Audio checkbox in the Playback Control tab of the System Settings window.