Apple Final Cut Pro 7 - Manual (Page 1426)

Red render bars in Safe RT mode become orange in Unlimited RT mode, indicating that
Final Cut Pro may drop frames during these segments to achieve real-time playback.
Orange status bars indicate
Unlimited RT playback.
Note: Segments that can play back without dropping frames still appear with colored
render bars as they would in Safe RT mode.
Unlimited RT mode uses the playback video quality and frame rate options you choose
in the RT pop-up menu or the Playback Control tab. However, this mode overrides the
Play Base Layer Only option and attempts to calculate all applied effects. For more
information, see
“Play Base Layer Only.”
Unlimited RT performance varies greatly depending on the effects in your sequence, the
codec and data rate of your media, and the processing power of your system. Some
segments of your sequence may play back without dropping any frames, while other
sections may rarely update the Canvas.
Tip: Turning on Unlimited RT is the only way to turn on third-party FXScript filters and
transitions to play in real time, if they’re capable of doing so.
Play Base Layer Only
The Play Base Layer Only option takes a unique approach to playing back
processor-intensive segments. With this option selected, any segment that requires
rendering in Safe RT mode (in other words, any segment with a red render bar) is restricted
to original media playback, and all effects, including compositing modes, are turned off.
Here are the playback rules for the Play Base Layer Only option:
• Effects that can be played back in real time are played just as they would be in Safe RT
mode.
• If a clip has effects applied, the effects are ignored if they can’t be played in real time.
Only the underlying clip media is displayed.
1426 Chapter 84 Using RT Extreme