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335 ADOBE PREMIERE 5.0
User Guide
Appendix A: Measuring Time
and Frame Size
ideo editing uses established measurement systems that address the specific require-
ments of working with video. Consistent measurement is important because video
is typically transferred between many kinds of software and hardware in the course
of video production. Understanding the measurement systems helps ensure that your video
program works well when transferred from one medium to another. This appendix describes
how time and frame size are measured in video editing.
Measuring time
A video program is defined by visual and audio changes that happen over time. Editing often
requires more precision than can be measured using hours, minutes, and seconds, so smaller
time spans are measured using the frames that make up each second.
A project can contain clips from many sources that may count time in different ways. The time
options in Premiere let you define how time is to be counted so that all clips can be edited
together and played back precisely and consistently.
Timebase
The timebase for your project specifies the number of time divisions per second by which
Premiere will calculate the precision of your edits. The timebase is not the same as the frame
rate, though they can use the same value.The timebase serves as a basis for time calculation,
whereas the frame rate is the rate at which the final video program plays back frames. In
general, choose 24 for editing motion-picture film, 25 for editing PAL and SECAM video,
29.97 for editing NTSC video, and 30 for other video types. Premiere also provides the
Frames/Samples option for counting frames or audio samples without referring to time.
For information about setting the timebase, see “General settings” on page 59.
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