What the heck?

525/59.94 DV uses 4:1:1 chroma subsampling. The coarse chroma resolution causes all sorts of steppy edge problems in chroma keying and in "upconversion" to 4:2:2 or 4:4:4 output formats.

Some DV codecs, like Avid's, filter or smooth the chroma on decompression (details here). Others, like Matrox's, let you turn chroma filtering and interpolation on or off as you see fit. But the Apple codec used in Final Cut Pro doesn't give you any choice: it's steppy edges, all the way.

I got tired of trying to fix the problem with the matte chokers, so I wrote FXScripts for  (a) a chroma blur and (b) a Y/C offset, to make keying easier and better, and to improve the quality of still frames I pull from DV footage in FCP.

FCP Plugins

Note: if you have Final Cut Pro 4 or later, Apple supplies two filters for chroma smoothing, one for 4:1:1 and one for 4:2:2. They reside in Effects > Video Filters > Key and are called "Chroma Smoothing - 4:1:1" and "Chroma Smoothing - 4:2:2" respectively.

They work differently from my H. Chroma Blur; usually they work slightly better, but once in a while my filter looks nicer, and my filter is adjustable. Futhermore, I find I still use my Chroma Offset filter on occasion, so it doesn't hurt to grab my filters even if you're using FCP 4.


• H. Chroma Blur (Video Filters > Blur) smooths the "steppy edges" resulting from DV's 4:1:1 chroma subsampling and the Apple DV codec's uninterpolated decompression thereof.

Use this filter on video clips where:

• you are applying Chroma Keyer, Blue and Green Screen, or Color Key keyers (add H. Chroma Blur first);
• you are putting the DV clip in an uncompressed (4:2:2 or 4:4:4) timeline;
• you are exporting stills, still sequences for film-out, or upconverting to HD.

This blur works for 4:1:1 DV and DVCAM (NTSC) and DVCPRO (NTSC & PAL). It's also useful for 4:2:2 clips when keying, exporting stills, going out to film, or upconverting to HD, if your 4:2:2 codec does not interpolate chroma.

The default setting of 3 usually seems to be the most suitable setting for 4:1:1 material, but you can change it if you like.

Unfortunately the filter is not useful for PAL DV/ DVCAM clips decompressed with the Apple DV - PAL codec. I am still working on a suitable filter for DV - PAL's 4:2:0 decompression, but it might take a while: 4:2:0 is a very difficult sampling scheme to recover decent images from.


• Chroma Offset (Y/C delay) (Video Filters > Channel) repositions the chroma of the image with respect to the luma in one-pixel steps. It's useful for re-aligning Y/C delay errors on analog and some digital source material, and is most useful in fine-tuning chroma key positioning: often ofsetting the chroma by -1 or -2 horizontally makes for a better key.

Download these suckers (binhexed Stuffit archive, 144kBytes )

When unstuffed, drag the "AJW's Filters" folder to your plugins folder:

• OS X: [Startup disk] > Library > Application Support > Final Cut Pro System Support > Plugins
• OS 9: [Final Cut Pro folder] > Plugins. Your FCP folder may be at the root of the disk (FCP 2 and earlier) or in the "Applications (Mac OS 9)" folder (FCP 3).

Legalese: These FXScripts have been tested with FCP 1.2.5, FCP 2.0, FCP 3.0, FCP 3.0.2, FCP 3.0.2, and FCP 4.0, however they are supplied as-is with no warranty of fitness whatsoever: install and use at your own risk. These FXScripts are freeware. They are not encoded, so if you don't like them, you can change them as you see fit. No email support will be provided (remember what you paid!), but if I get consistent bug reports and/or questions I'll update the plugins and/or this page as needed.

Copyright (c) 2002-2003 by Adam J. Wilt.
You are granted a nonexclusive right to reprint, link to, or frame this material for educational purposes, as
long as all authorship, ownership and copyright information is preserved and a link to this site is retained.
Copying this material for a publicly-accessible website (instead of linking to it) is expressly forbidden except
for archival purposes: this page is dynamic and will change as time goes by, and experience has proven that sites
copying my material do not keep their copies up-to-date, thereby doing their visitors, themselves, and me a disservice.