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Final Cut Pro Quick Tip #8

De-Interlacing By Stephen Schleicher
I received a DV tape the other day that was dubbed from a VHS tape. Popping the tape into my Sony deck I instantly saw something that the person who dubbed the tape over looked; the person didnt use a TBC when making the dub and the video had jumped up approximately 50 lines. Solution? Modify the size of the image in Final Cut Pro 3.0. But that is only part of the solution. This Final Cut Pro Quick Tip explains how.

While increasing the size of the video solved the faulty video image, it also presented other problems. Because NTSC video is interlaced, whenever you increase the size of an image you are also shifting those scan lines to other regions of the screen. Scan line 1 may now be positioned at scan line 2, thus throwing off the field interpretation. This will result in jumpy, stuttering video, very noticeable scan lines when exported to video.


The best solution I have found so far that works whenever you are panning, zooming (scaling), or animating a video layer is to use the De-Interlace filter. The De-Interlace filter works by removing either the upper (odd) or lower (even) field of information from any interlaced video. With only one field remaining, Final Cut Pro 3.0 interpolates the remaining information to recreate a whole image.

Footage before de-interlacing


Footage after de-interlacing. Notice how the diagonal lines are now much softer than before.


As can be seen in the above images, the De-Interlace filter solved the problem of the poor quality of the video with only some slight softening of the image (which actually improved the poor quality VHS dub in my opinion).

You could also use the De-Interlace filter if you are trying to create a still image from a video clip. Often if people or objects are moving, the fields capture the movement in different positions causing a jittering of the still frame. Jittering will also occur in images that have very thin one pixel lines that can decide if they want to reside in field one or in field two. By removing and interpolating, Final Cut Pro does an excellent job in creating the still image you need.

The one drawback of the De-Interlace filter is that it is not a real time effect and you will have to spend a considerable amount of time rendering a clip for use in your project. For short clips, this will not present a problem, but for longer clips, expect a wait.

Apple suggests using the De-Interlace filter on your project if you are planning on exporting your video project to QuickTime or to other streaming format. Because of the render times involved, I would not use the De-Interlace filter for that purpose. Instead use the QuickTime de-interlace option found in the export command or in the video compression program of your choice (like discreets cleaner 6.0). This way you are free to work and make changes, without having to re-render every couple of minutes. De-interlacing works great when you are animating a video layer, but not that practical for web streaming.



In the end, I was quite pleased with how the poor VHS to DV dub turned out in the project, and the client thought it looked good (she couldnt tell that the footage had been altered). Next time you need to animate a layer and the image jitters too much, youll know to use the De-Interlace filter to solve your problem.

Here is a current list of the Final Cut Pro Quick Tips to date:
Final Cut Pro Quick Tip #1: Texture Treatments to Enhance Video Productions
Final Cut Pro Quick Tip #2: Using Markers to Quickly Edit a Music Video
Final Cut Pro Quick Tip #3: Import Your Music the Right Way
Final Cut Pro Quick Tip #4: Nesting Helps Manage Longer Projects
Final Cut Pro Quick Tip #5: Keying Explained
Final Cut Pro Quick Tip #6: Configuring Your Scratch Disk
Final Cut Pro Quick Tip #7: My Favorite Effects


When not working deep in the labs of the DMN Central Division testing the latest and greatest software/hardware products Stephen Schleicher can be found at the local university teaching a few courses on video and web production. He can be reached at schleicher@mindspring.com. You can also visit him on the web at www.mindspring.com/~schleicher


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Stephen Schleicher is a well known writer, visual effects artist and media guru! You can see more of Stephen at
www.majorspoilers.com and www.stephenschleicher.com
Related Keywords:final cut pro, fcp, apple, de-interlace, filter, effect, tutorial, schleicher

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