The Shifter

Why shifting fields?

Most video is field based. Using an NLE system always two fields are integrated into one frame. The computer (NLE) always 'outputs' frame - the video device will use fields.
Using PAL as TV standar
d, the order how those fields/pictures are displayed varies. With standard video the fields are displayed in a ‘normal' sequence i.e. field 1,2,3,4,5,6,… Using DV25(or 50 or 100) the sequence order changes to 2,1,4,3,6,5,….

But what does this mean in practice?
Following is a PAL only issue.
Putting SD footage into a DV25(or 50 or 100) sequence will result in a flickering video. The reason is easy to understand, if you look at the picture sequence as a number of actions.
Standard video records and plays back in this way: 1st action, 2nd action, 3rd action etc.
DV25(or 50 or 100) does it different in the way of sorting those actions: the 2nd action will be first in the way it is stored on tape the 1st action will be number two in this sequence and so on.
So if you play back a standard (PAL or NTSC video) action sequence of a horizontal forward moving object with DV25(or 50 or 100) it will be displayed like: startpoint, action before startpoint, two actions further in the timeline, one action back in the timeline, two actions further in the timeline … - somehow it's like real life - a never ending forth and back.
The same would happen if you put DV into a standard PAL sequence.

Something all TV standards have in common
is that the field order must change, if you reverse the video playback.

Here is why (reads somehow complicated - but ...)

If you have the fields ordered with PAL DV or any NTSC format (using the numbered actions again - Frame # = action#x,action#y) is will look like the following:
Frame 1 = storing 2,1 reading 1,2
Frame 2 = storing 4,3 reading 3,4
Frame 3 = storing 6,5 reading 5,6
Frame x = storing etc reading ...
The result is 1,2+3,4+5,6...

doing that backwards will give following result :
Frame x = storing etc reading ...
Frame 3 = storing 6,5 reading 5,6
Frame 2 = storing storing 4,3 reading 3,4
Frame 1 = storing 2,1 reading 1,2
The result is ...,5,6+3,4+1,2, which is obviously not this kind of order we want to have

If you have the fields ordered with standard PAL it will look like the following:
Frame 1 = storing 1,2 reading 1,2
Frame 2 = storing 3,4 reading 3,4
Frame 3 = storing 4,5 reading 5,6
Frame x = storing etc reading ...
The result is 1,2+3,4+5,6...

doing that backwards will give following result :
Frame x = storing etc reading ...
Frame 3 = storing 5,6 reading 5,6
Frame 2 = storing 3,4 reading 3,4
Frame 1 = storing 1,2 reading 1,2
The result is ...,5,6+3,4+1,2, which is the same bad result as above.

If your NLE or VFX software does not support a real field reverse, the result could look poor.

Here come the 'Shifters'.
It's the tool, that helps You to make Your video look better under following circumstances:
it should be rendered with reverse speed within Final Cut Pro
You mirrored Your clip for some reason.
You want to mix DV-PAL and standard PAL Codecs within the same timeline.

How does FCP Shifter work?
Just simple - the filter moves down your video one pixel. Reversed, vertical mirrored and PAL DV in PAL SD (or the other way round) will look fine.

The bad thing about this way of conversion is - if you have done it often enough your video disappears since it's shifted out of the viewable area.

How does The Shifter work?
The Shifter does what it name says - it will shift the the video track one line down. So any field 1 will be field 2, field 3 will be 4 and so on.

The tool uses a little trick with QuicktTime Player: it moves the timecode track of the movie one pixel down - the video track follows the timecode and the resulting movie is exactly one pixel higher in vertical size - which means the former first line of the video track now becomes the second line of the new movie.

The bad thing about this way of conversion is - we introduce new video formats, which are slightly higher than normal, and you will loose one field at the bottom of each the frame (in your final edit).

The new movie will be saved as a referenced file, so Your original footage won't be affected by this changes.This has some additional advantages: within the NLE you always can decide which parts of the footage you will use (and must be rendered) that can save a lot of disk space

Using Final Cut Pro (unfortunately - as said above) the new size of the movie is something totally unknown to FCP and the software will interpret the footage with the wrong aspect ratio. So You must reset the ratio to 0 by hand (since FCP doesn't create a 'Motion Favorite' for this), but You can use the 'Paste Attributes' feature, if You got a lot of movies to change.
After this procedure even FCP believes that you have a movie with a different field order (independent from the format you're using) and you are ready to render the clip.

The Shifter also allows You to select multiple files and folders to convert them with a batch process.

Example for reverse video in FCP (DV 5.6 MB .sit format) to see the difference the movie must be displayed on a TV monitor.

Requirements

FCP Shifter:
You need FCP.
Download FCP-Shifter

The Shifter:

Skilled user who really read and understood the text above and the limitations of The Shifter,
a
machine running Mac OS X 10.2.x, or higher
QT Pro 6.x or higher
Movie with Timecode Track

Download .sit
Download .hqx

Contact me @ andreask@finalcutpro.de