[opendtv] Re: A bit OT: 24 Frames Drop Frame Timecode

Russ,
I would start with going back to the customer who 'requested' this feature of your closed captioning software and ask them how they are creating 23.976 drop frame timecode.
As far as I can tell, and as I'm sure your own research has confirmed, there is no standard for generating 23.976 drop frame timecode, so I'm puzzled why they're asking for a feature that doesn't exist. 

John

P.S.  The Masked Engineer:

http://www.tvtechnology.com/features/Masked-Engineer/
"Mario Orazio is the pseudonym of a well-known television engineer who wishes to remain anonymous. Send your questions or comments to him c/o TV Technology. Or drop him a note on e-mail Mario_Orazio@xxxxxxxxxxx ."
----- Original Message ----- From: "Russ Wood" <russ.wood@xxxxxxxxxxxx> 
To: <opendtv@xxxxxxxxxxxxx>
Sent: Tuesday, December 11, 2007 10:40 AM
Subject: [opendtv] Re: A bit OT: 24 Frames Drop Frame Timecode



Thanks for all your replies so far, it has been quite a healthy debate.

John Shutt mentioned the "Masked Engineer" - I haven't noticed him on
this list before, is there a thread with his (I assume it is a he)
exploits.

The option of using a lookup table for which frames to drop appeals but
as there are 2,071,528 frames in a day you would need 258,941 bytes to
hold this, that might be noticed even on a PC.  You could optimise this
by realising that it is only the 00 and 01 frame values that would be
dropped.

The idea of dropping every 1001 counted frame would be OK but we need an
algorithm that ensures that everybody always drops the same framecount
numbers even if they start from different timecodes.  So you can't start
from 10:00:00:00 and drop every 1001st count, you have to calculate what
the count would be at 10:00:00:00 (modulo 1001) and start from there.

I have had contact with Evertz and they have confirmed that they do not
implement 23.97 fps drop-frame timecode.  If nobody else is implementing
23.97 drop-frame am I worrying too much (or is it just too soon)?

Thanks again - Russ Wood


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