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Re: Forced A Frames

Gary Adams wrote:
> A bit of history.  The "0" and "5" frame rounding for "A" frame
> transfers came from a meeting quite some time ago between Time Logic
> and other vendors and customers as a method of simplifying the Dailies
> Logging process.  Certainly "A" frames may be placed starting with the
> first field of any video frame, either drop or non-drop.  Forcing the
> "0" and "5" frame timecode values made it easier to check visually.
> This method was also defined using non-drop timecode.  You could start
> out using this method for drop frame code, however, the numbers would
> drift off the "0/5" boundaries right after the first dropped frames.
> There is nothing wrong with using drop frame code here either, it's
> just the numbers will not always conform to a fixed pattern "0/5",
> "1/6" or whatever.  The system should still work.
> I keep hearing from customers that some non-linear editing systems
> don't "like" timecode values other than "0" and "5".  This is probably
> not entirely true, however, it is possible some software versions of
> these editing systems may be sensitive to these values.  Quite often,
> the dailies customer wants this method just to eliminate another
> variable in the complicated process.
> The TLC was designed to force the "0/5" relationship while in A Frame
> mode using non-drop frame timecode.  If drop frame timecode is used,
> the A frames remain accurate, but will not have the familiar pattern of
> numbers.  There are ways of providing other relationships with the TLC
> with careful setup and using special macro keys.  You should be able to
> do this with most any version of TLC hardware or software.
> The bottom line is accurate data.
> Contact me directly if you have any questions.
> Gary Adams
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> inquiries to rob at alegria.com...http://www.alegria.com/telecinehome.html

You are correct, it is more of an historical issue than anything else.
The original Lightworks had as a stated requirement that the SMPTE A
frame always be on a timecode number evenly divisible by five. The
current Lightworks and Avid Film Composer do not require this
relationship. It is enough that the 3:2 relationship be correctly
indicated in the database (although Avid's represetation of C and D
frames always seemed a little strange to me). It makes life easier for
the assistant editors to always expect A frames on 0's and 5's so it has
become standard practice for us. 

Martin Zeichner