FCP X: Interlace and Deinterlace

Posted on by Larry

logo-FCPXPersonally, interlacing can’t go away fast enough to suit me. Unfortunately, interlacing will be with us for many more years, so we need to learn how to deal with it.

The process of converting an interlaced clip to a progressive clip is called “deinterlacing.”

Interlacing began in the earliest days of television to solve problems related to displaying moving images, and continues today because it reduces the bandwidth necessary to transmit or cablecast HD video.

NOTE: The web always prefers progressive video. However, many cable and broadcast outlets require interlacing, which is why this problem persists.

What interlacing does is divide an image into two “fields,” where all the odd-numbered lines in the image are in Field 1, while all the even-numbered lines are in Field 2. In and of itself, fields are not a bad thing. The problem is that when we shoot an interlaced image, there is a slight time difference between when the two fields are recorded. For stationary images, this isn’t a problem. But, moving objects in the frame develop thin horizontal lines corresponding to the time difference between Field 1 and Field 2.

Here’s an example of interlacing. Notice the thin lines radiating horizontally from the speaker’s moving hand?

NOTE: This is why, whenever you shoot video, always shoot progressive images. It is very easy to convert progressive to interlaced. Converting interlaced to progressive – though FCP X makes it easy – always diminishes image quality.

ADD PROGRESSIVE VIDEO TO AN INTERLACED TIMELINE

Adding a progressive clip to an interlaced timeline is easy. Just edit it in. Final Cut automatically converts it to interlaced and there is no drop in image quality.

NOTE: UHD and 4K images are always progressive.

ADD INTERLACED VIDEO TO A PROGRESSIVE TIMELINE

In either the Browser or the Timeline, select the interlaced clips you want to deinterlace.

Open the Inspector (Cmd + 4) and click the Info text button at the top.

anamorphic003

In the lower-left corner, change the popup menu to Settings.

Then, check the Deinterlace checkbox.

Fixed.

NOTE: Selecting the Deinterlace setting causes the frame rate of the selected clips to double. For example, if the original interlaced clips have a frame rate of 29.97 fps, the deinterlaced clips will have a frame rate of 59.94 fps.

VERIFY YOUR CLIPS

As you can see in this screen shot of a moving hand, deinterlaced clips will, most often, appear a bit softer than a progressive image. This is the result of the deinterlacing process.

To verify that the interlace artifacts are gone (i.e. those thin horizontal lines) set the Viewer to 100% view, Better Quality, then press the left or right arrow keys and look at the image in the Viewer.

Depending upon the speed of your system, deinterlaced clips may require rendering.


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35 Responses to FCP X: Interlace and Deinterlace

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  1. Matt says:

    HELLO.! ANYBODY??

    So just spent 6 weeks editing a big job..using edits from my old imac and FCP older version..I exported the projects to the new FCPX 10.4 and new mac..Went to export the final edit and the interlace issue was SHOCKING!! I never had this problem with the same project/clips in the old mac/FCP…Does anyone know the workflow starting with formats to record to on my Canon 5D and then to the new FCP 10.4 to avoid the interlace issues??…any suggestions appreciated as I’m going to lose my mind with it due to the fact I need to hand over the job in 4 days..thanks in advance

    • Larry says:

      Matt:

      Actually, you did have this problem with the old version of FCP 7, however, QuickTime Player 7, by default, never displayed interlacing. It only displayed one field, which made it look like nothing was interlaced, when, in fact, it was. You needed to change an internal setting to display interlacing. Quicktime Player X defaults to showing interlacing. The problem was there, all the time.

      You can solve this issue two ways:

      * Edit and export your interlaced footage as normal. Then, use Compressor to deinterlace. Here’s an article that explains how: https://larryjordan.com/articles/compressor-how-to-deinterlace-video/

      * Or, you can select all the clips in the timeline, go to Inspector > Info, open the Settings menu and check “Deinterlace.” This will deinterlace all clips in the Timeline at once.

      My general preference is to deinterlace during compression, but try both and see which one works the best.

      Larry

  2. Robert Post says:

    Hi Larry,
    First off, thank you so much for this post!
    I’m having a problem getting horizontal lines (which I assume is an interlace issue) off some older footage that I imported into FCP 10.4. The footage is SD 720 x 480 from a canon xl1. I’ve tried checking the ‘Deinterlace’ box under Info, but it doesn’t change a thing to the footage.
    You mentioned that “the project also needs to be set to deinterlace,” but I can’t find anywhere to set the project to deinterlace.. not sure what I’m missing here, but it’s driving me nuts.
    Any help is much appreciated!! Thank you again for posting such great content.
    Best,
    Rob

    • Larry says:

      Robert:

      I’ve found it best to import and edit interlaced footage as interlaced. Export a master file that’s also interlaced. This way, you have the highest quality image possible edited and saved for the future.

      Then, remove interlacing during the compression stage. Compressor is good for this, as is Adobe Media Encoder and other compression applications.

      Larry

  3. swstanton61 says:

    Can anyone tell me where the deinterlace option is located in FCP X 10.4? Still trying to find things with the new menu layout!

    • Larry says:

      SWStanton61:

      Deinterlacing happens automatically when you drop an interlaced clip into a progressive project.

      If you need to preserve interlacing, make sure the project, itself, is interlaced. For example, a 1080i project is interlaced. A 1080p project is progressive.

      Larry

      • Gretta Wing Miller says:

        “Deinterlacing happens automatically when you drop an interlaced clip into a progressive project.”
        This is exactly opposite of what you said in the body of the article!

  4. Reshma GHosh says:

    Hi Larry ! Your articles have been a great help – exporting from FCP x for a Singapore Boradcaster and they need the master in an interlaced format. I’ve followed your instructions and changed the project timeline to interlaced so that should help. So in the Inspector – for the Field Dominance Override – I’ve selected ‘off’. Hope that shouldn’t be an issue? Pl. let me know, Thank you !

    • Larry says:

      Reshma:

      This should be fine – but running a quick test to make sure is always a good idea. Deliver a sample video to your broadcaster ahead of deadline and make sure it meets their specs.

      SD is lower-field dominant. HD is upper-field dominant.

      Larry

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