Apple Final Cut Pro 7 - Manual (Page 1425)

Safe RT
The Safe RT mode guarantees that effects are played back at the quality and frame rate
you specify and that no frames are dropped during playback. If Final Cut Pro anticipates
that your computer won’t be able to perform all the effects calculations in real time, the
render status bar for that segment becomes red, which means you have to render before
you can play back.
Red render bars indicate
rendering is required.
Before using the Print to Video or Edit to Tape commands to output to tape, you can
switch to Safe RT mode to see how many segments require rendering.
Important: Even though the Safe RT option guarantees that no frames will be dropped
because of processor limitations, frames may still be dropped if your scratch disk cannot
maintain the necessary data rate during playback. This can be a problem if you have
multiple video streams playing from a relatively slow hard disk. In this case, the Timeline
may show a green render bar, indicating that the processor can handle the effects load,
but you may still drop frames because of slow disk performance. To solve this issue, you
can limit the acceptable real-time data rate of media playback in the General tab of the
User Preferences window. For more information, see
“Choosing Settings and Preferences.”
Unlimited RT
Choosing this option tells Final Cut Pro to play as many frames as possible when your
effects exceed the processing power of your computer. Final Cut Pro does this by spending
time to process some frames in real time while skipping others completely. Unrestricted
real-time playback allows you to play more effects but increases the likelihood that your
sequence will drop frames during playback. This mode is useful for getting a real-time
preview of complex effects compositions. Embedded Motion projects can also be played
back in this mode.
1425 Chapter 84 Using RT Extreme