Apple Final Cut Express 4 - Manual (Page 920)

920 Part X Real Time and Rendering
Determining Whether Clips in a Sequence Will Play Back
in Real Time
When a sequence contains a clip whose media file format doesn’t match the sequence
format, the clip plays back in real time only if:
 The clip’s media file format and the sequence format are both supported by the
Final Cut Express real-time playback engine
 Both the clip and the sequence have a frame rate supported by Final Cut Express.
The following frame rates are supported: 25 and 29.97 fps.
 Your computer has enough processing power to handle the real-time playback of
both the clip and sequence formats. For example, if you are using a portable
computer, you won’t be able to play back uncompressed video.
Terminology for Discussing Mixed-Format Sequences
The following definitions provide some shorthand for discussing the behavior of
sequences containing mixed formats:
 Format: The defining characteristics of a video media file—image size, frame rate,
and codec
 Native sequence: A sequence containing clips whose media files match the
sequence format
 Mixed-format sequence: A sequence containing clips whose media files don’t match
the sequence format
 Nonmatching clip: A clip whose media file format doesn’t match the sequence format
 Real-time nonmatching clip: A nonmatching clip that plays back in real time in a
mixed-format sequence (real-time clip for short)
 Non-real-time nonmatching clip: A nonmatching clip that cannot play back in real
time and therefore must be rendered (non-real-time clip for short). In previous
versions of Final Cut Express, all nonmatching clips were non-real-time clips.