Apple Cinema Tools 3 - Manual (Page 120)

120 Chapter 6 Preparing the Source Clips for Editing
About “A” Frames
If your video has window burn, the easiest way to locate an A frame is to look at the
key number in the video frame, which typically has a letter after it indicating the
frame type. This letter is called the frame type indicator. “A” frames include any frame
with a frame type indicator that begins with A, including an AA (also known as A1A2),
AB (also known as A2B1), A1, or A2 frame. When viewing the video a frame at a time,
the frame type indicator for an A frame shows an A while the frame number is solid
(not flickering between two frames).
If you are using non-drop frame timecode and your source clips have not yet been
edited, there is a reliable five-frame pattern where an A frame occurs every five
frames. Usually, any timecode number ending in 0 or 5 is an A frame, for example,
1:23:14:10 and 1:23:14:15.
During batch reverse telecine, if a clip starts on a timecode number that is not
evenly divisible by five (that is, timecode numbers ending in 5 or 0), Cinema Tools
trims frames from the beginning of the clip so that the clip starts on the next
timecode that ends in 0 or 5. This is done to make sure that all source clips start on
an A frame. Clips that are trimmed are noted in the batch reverse telecine log file,
which is named reverse.log.
When key numbers are not burned in to the video, finding an A frame is much more
difficult. If there is a lot of motion in the video, you might be able to distinguish one
of the original film frames from the next in the video. In that case, look for a video
frame made up of two fields from the same original film frame, which has different
film frames before and after it. Such a frame would be an A frame.
The frame type indicator in
the window burn tells you
this frame is an A frame.
UP01101.Book Page 120 Thursday, March 10, 2005 3:16 PM