[tig] 720p 60Hz odd/even frame identification

David L. Tosh dlt
Fri Aug 29 03:41:03 BST 2003


At 1:58 PM +0200 8/28/03, jp wrote:
>   When transferring a 30fps shot film to 72OP 60Hz
>   you get two identical video frames per film image,
>   and there is no indication in the HD signal
>   out of the telecine to differentiate the first
>   from the second one.

Even in the more common case of 24fps film transferred to 720P 60, 
there is no signal "in the HD signal out of the telecine." I assume 
that both extant manufacturers of HD telecines have no provision to 
put ancillary data in the optional HD outputs. It would be nice if 
they did make this provision but it might also eliminate some sales 
of after-market RP-215 telecine data inserters.

I am not close to a Spirit (or up to date documentation) but I wonder 
if the FRID pulse used for 2:3 information would be suitable for 
flagging the first new frame of a 2:2 sequence (25fps film in a 
720P50 recording is another case.) Someone from Thomson and someone 
from Cintel should jump in here.

But since these are truly *identical* frames (not fields) and, since 
there is no concept of even/odd until it gets recorded to tape with 
timecode, it doesn't really matter. The timecode will run at 30fps 
but the first frame of a new timecode number will always be unique 
from the previous timecode number. The TLC can enforce pairing of 
identical frames in the same timecode 30 Hz frame like the TLC can 
enforce a 2:3 pattern alignment. (Right Gary?)


-- 

David Tosh
<dlt at earthlink.net>





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