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 First Post -->Q on "Drop Frame?" 
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Joined: Tue Nov 23, 2010 6:10 am
Posts: 1
Post First Post -->Q on "Drop Frame?"
My first post here, thanks for all the groovy stuff here including this forum. Some keen videos and such.

Last evening I did a very hastily impromptu first "TEST" time lapse video. It went about as I expected and know I'll be tweaking all things including my post picture work flow.

--->But a likely dumb question out of the gate: Do most of you use "Drop Frame" on your exports? I do as it is kind of a generic norm for the simple stuff that I do ....and while playing last night I was shocked to find the impact it made on my simple little test TL video. This one I did in PremElements for simplicity:
Image

---> Simple Video Here With Showing Variation Of Drop Frame:

GO HERE:
http://www.goraiders.org/misc/videos/mi ... Frame.html

----> (and don't give me any shit, this is my first post, ---but 2nd post you can bring the shovels.) :-)


Tue Nov 23, 2010 6:21 am
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Joined: Tue Apr 29, 2008 2:48 pm
Posts: 1144
Post Re: First Post -->Q on "Drop Frame?"
from wikipedia:

Drop frame timecode

Drop frame timecode dates to a compromise invented when color NTSC video was invented. The NTSC re-designers wanted to retain compatibility with existing monochrome TVs. Technically, the 3.58 MHz (actually 315/88 MHz = 3.57954545 MHz) color subcarrier would absorb common-phase noise from the harmonics of the line scan frequency. Rather than adjusting the audio or chroma subcarriers, they adjusted everything else, including the frame rate, which was set to 30/1.001 Hz.
This meant that an "hour of timecode" at a nominal frame rate of 30 frame/s was longer than an hour of wall-clock time by 3.59 seconds, leading to an error of almost a minute and a half over a day. This caused people to make unnecessary mistakes in broadcasting studios and precious advertising dollars could be lost.[citation needed]
To correct this, drop frame SMPTE timecode was invented. In spite of what the name implies, NO video frames are dropped (skipped) using drop-frame timecode. What's actually being dropped are some of the timecode "labels". In order to make an hour of timecode match an hour on the clock, drop-frame timecode drops frame numbers 0 and 1 of the first second of every minute, except when the number of minutes is divisible by ten (i.e. when minutes mod 10 equals zero). This achieves an "easy-to-track" drop frame rate of 18 frames each ten minutes (18,000 frames @ 30frame/s) and almost perfectly compensates for the difference in rate, leaving a residual timing error of roughly 86.4 milliseconds per day, an error of only 1.0 ppm.
i.e. - Drop frame TC drops two frames every minute, except every tenth minute, achieving 29.97frame/s.
Drop frame is usually represented with a semi-colon (;) or period (.) between the seconds and frames whereas non-drop retains the colon (:). The period is usually used on VTRs and other devices that don't have the ability to display a semi-colon.
Example: drop frame = "HH:MM:SS;FF" or "HH:MM:SS.FF", non-drop frame = "HH:MM:SS:FF"

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Tim T


Tue Nov 23, 2010 9:36 am
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