Drop frame | ![]() |
Colour video was slowly introduced
into broadcast. It was therefore necessary to make it compatible
with black and white receivers and to design colour receivers or televisions
to be able to receive black and white programming as well. In order
to accommodate the extra information needed for colour the b&w’s 30
frame/second rate was slowed to 29.97 f/s for colour. Although usually
not an issue for non broadcast applications, in broadcast, the small
difference between real time (or the wall clock) and the time registered
on the video can be problematic. Over a period of 1 hour (SMPTE) the video
will be 3.6 seconds or 108 extra frames longer in relation
to the wall clock. To overcome this discrepancy drop frame is used.
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Drop frame: Every frame :00 & :01 are dropped for each minute change (60 X 2 = 120) except for minutes with 0’s (00:, 10:, 20:, 30:, 40: & 50:) (6 X 2 = 12, 120 - 12 = 108) | ![]() |