Apple Final Cut Pro 7 - Manual (Page 1820)

Real-Time Audio and Video Options
• Real-time Audio Mixing: Enter a number in this field to specify how many audio tracks
can be mixed in real time. The default is 8 tracks, and the maximum is 99. The maximum
number of tracks that can be mixed without having to be rendered is affected by your
computer’s processing capabilities, the number and types of filters used in your
sequence, the data transfer rate of your hard disk, and the amount of memory available
to Final Cut Pro.
• Audio Playback Quality: This pop-up menu affects the quality of sample rate conversions
(when your audio clips have a different sample rate than the sequence that contains
them) and transitions between rendered and nonrendered sections in the Timeline.
• Low (faster): This choice yields the best real-time audio performance, but the lowest
sample rate conversion quality. When the playhead moves from rendered to
nonrendered audio segments in the Timeline, there may be an audible click or a
distracting shift in levels. For basic editing, this is usually the best choice.
• Medium or High: When you start to do detailed mixing of your audio tracks, you may
want to raise the audio mixing quality to Medium or High. Higher-quality sample
rate conversions sound better, but require more processing power and thus limit
the number of simultaneous tracks you can work with in real time. Also, shifts between
rendered and nonrendered audio segments sound smoother. Final Cut Pro always
uses the highest quality setting (regardless of what is chosen in the Audio Playback
Quality pop-up menu) when rendering, mixing down audio, editing to tape, printing
to video, or exporting audio and OMF files.
• Limit real-time video to N MB/s: Final Cut Pro uses this number to limit how many video
streams can play back from your scratch disk in real time. This is useful when multiple
editing systems are sharing the same media (such as a storage area network, or SAN),
or when you have a scratch disk with a limited data rate, such as a portable computer
hard disk.
For example, suppose you try to play a sequence with six simultaneous video tracks
containing DV media, and Final Cut Pro warns you that frames were dropped during
playback. If you then try to play a sequence with five simultaneous video tracks and
no frames are dropped, you know that your scratch disk can handle no more than five
simultaneous DV video streams. Since DV has a data rate of 3.6 MB/sec., you can select
the “Limit real-time video to” option and enter 18 MB/sec. (5 x 3.6 MB/sec.) in the number
field. Now, if a sequence requires a sustained data rate of more than 18 MB/sec. for
playback, Final Cut Pro shows a red render bar over this portion of the sequence.
Note: Final Cut Pro always allows a single video stream to play, even if the data rate
limit you set is below the data rate of a single video stream. For example, if you set the
data rate limit to 1 MB/sec., Final Cut Pro would still play back a single DV video stream,
even though its data rate is 3.6 MB/sec.
1820 Chapter 111 Choosing Settings and Preferences