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How to UNDO incorrect Advanced Pulldown Removal

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Bill RussellHow to UNDO incorrect Advanced Pulldown Removal
by on Dec 18, 2012 at 4:16:16 am

Hi, I have a client who tried to remove pulldown using the "Remove Advanced Pulldown" tool in Final Cut Pro. The clip was NOT advanced (2:3:3:2), but normal (3:2) cadence. The removal of coursed messed up the resulting 23.976 clip and it is now unusable with random mixed-field frames, and they don't have a source to go back to.

I asked for a copy of the clip, and I've been looking at its Quicktime metadata in Atom Inspector, but I can't find anything obvious. Anyway, I have no ideas how to remove faulty advance pulldown removal. It must be possible, as Quicktime is simply suppressing the third of every five frames. Any brilliant ideas appreciated!

"THE LOST SKELETON OF CADAVRA" -

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Joseph OwensRe: How to UNDO incorrect Advanced Pulldown Removal
by on Dec 18, 2012 at 5:56:48 pm

[Bill Russell] "The removal of coursed messed up the resulting 23.976 clip and it is now unusable with random mixed-field frames"

Working through the math here...

What they started with was normal 2:3 field cadence according to what I am able to determine from the above. Typically that would be a SMPTE ABCD cadence. If there was an Advanced Pulldown removal applied (how did they do this?) which removes the third frame of every five-frame 29.97 or 59.94 group, what should result is 4 progressive frames. AP is 2:3:3:2, or SMPTE ABDA, so what gets removed is the third field of the B frame and the first field of the D frame, which are redundant and what you theoretically yield is an AAAA sequence. There is no C-frame in Advanced Pulldown, by definition.

What has been removed from the ABCD sequence though would have been the third field of the B frame and the first field /half frame of the C frame, leaving a mixed CD frame as the third progressive frame. This shouldn't be random at all unless there is something else going on. As you step through the 4-frame sequence you should notice that it is always the third frame that is mixed and will interlace/dither.

I fixed something like this once with one of the Nattress smart re-interlace filters which pulled out the C-portion on the upper dominant, and removed the D-portion, which really calmed down the motion artifacts.

If this pulldown removal was performed as a batch process on an edited/baked sequence, there is really no hope of regaining a coherent segmented field sequence.

I can see the big question marks over the heads of everybody at Apple... Huh??? What's a "field"????

jPo

"I always pass on free advice -- its never of any use to me" Oscar Wilde.


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Bill RussellRe: How to UNDO incorrect Advanced Pulldown Removal
by on Dec 20, 2012 at 1:40:13 am

Hello! Yes, you asked "How did they do this?" In Final Cut Pro 7 there are two pull-down removal tools.

One is "Cinema Tools Reverse Telecine" tool which uses the Cinema Tools engine. Cinema Tools is rather blunt and simply assumes that the cadence begins AA = :00, removes the pulldown based on that, writes a new 24p (23.976) file with the cadence removed, replaces the media with the new file of the same name, and relinks to the project. A completely new media file has been written.

The other tool is the "Remove Advanced Pulldown" tool. Since 24pA has all the needed frames already, plus the extraneous "BC" frame (third of every five frames), all this tool does is rewrite data WITHIN the existing file so that it skips the "BC" frame on playback. NO new media file is written.

This is my question. The media file contained a standard 3:2 cadence, but was mistakenly submitted to the Advanced Pulldown removal tool. Too easy. The media contained AA BB BC CD DD. 24pA contains AA BB BC CC DD, where the "Remove Advanced Pulldown" tool simply removes the one unneeded BC frame. The the resulting file contains AA BB CD DD instead of AA BB CC DD -- in other words, you are stuck with a mixed-interlaced "CD" every four frames. (You're right, that's not random.)

Since the Advanced Pulldown Tool does NOT replace the media file, only alters it to SUPPRESS playback of the third of every five frames, and correspondingly changes the TC count from 29.97 to 23.976 to restore correct speed, there must be a way to restore the five-frame playback and 29.97 count. (No, changing the count from 23.976 to 29.97 in Cinema tools does not work -- all it does is speed up the clip.)

I used Apple's Atom Inspector and compared headers of a media file before and after advanced pulldown removal, and could not find anything sensible. I don't even know if editing the headers is the right way to go, or how to HEX edit the file. But since the Advanced Pulldown tool does not have any kind of verification check, you can ruin any media file by accidentally choosing this tool. To me that means people have suffered this before, and I would think there must be a way to undo it, either legit or a kluge.

We would love to restore the playback and count of this file, so that we can then properly remove the standard cadence.

In other words... help! ;)

"THE LOST SKELETON OF CADAVRA" -

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Rafael AmadorRe: How to UNDO incorrect Advanced Pulldown Removal
by on Dec 25, 2012 at 1:11:05 pm

"QT Edit", from Digital Rebellion, might help you. Not sure but you should contact them.
http://www.digitalrebellion.com/promedia/features.html
rafael

http://www.nagavideo.com


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Bill RussellRe: How to UNDO incorrect Advanced Pulldown Removal
by on Jan 4, 2013 at 4:23:08 am

ooo, I missed this. On long holiday, will look into this. Thanks!

"THE LOST SKELETON OF CADAVRA" -

And more...


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