APPENDIX A
340
Measuring Time and Frame Size
duration. While tiny at first, this difference grows as program duration increases, preventing
you from accurately creating a program of a specific length.
Drop-frame
timecode is a SMPTE
standard that maintains time accuracy by eliminating this error. When you use drop-frame
time code, Premiere renumbers the first two frames of every minute, except for every tenth
minute. For example, the frame after 59:29 is labeled 1:00:02. No frames are lost, because
drop-frame timecode doesn’t actually drop frames, only frame numbers.
Premiere displays drop-frame timecode by displaying semicolons between the numbers in time
displays throughout the software, and displays non-drop-frame timecode by displaying colons
between the numbers in the time display.
Drop-frame timecode uses semicolons (left) and non-drop-frame
timecode uses colons (right).
When the precise duration of a program isn’t critical, such as for an in-house corporate
videotape, you may specify 30 fps non-drop-frame timecode, which doesn’t renumber any
frames. Drop-frame timecode was specifically designed for a 29.97 frame rate, so never use
drop-frame timecode for PAL or SECAM video, which display at exactly 25 fps.
Counting frames and samples
The ability to count individual samples of an audio clip in Source view can be useful. (Video
clips always display individual frames in Source view.) Although this is not an issue when the
audio source clip frame rate is equal to or lower than the timebase, it becomes important when
the audio source clip frame rate is higher than the timebase: If you want to start an audio clip
from a point that falls between timebase divisions, you need a way to work at a resolution finer
than that of the timebase. You can handle these situations using the Frames/Samples option for
time display, which counts individual frames or audio samples.
c00.book for PS Page 340 Tuesday, March 31, 1998 1:28 PM
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