Interlace.
As a digital filmmaker, interlace means only one thing; problems.

Interlace has been around in the NTSC standard since the beginning. It was a way to get more information over the limited bandwidth of broadcast television. Basically, Every other line of an image is displayed, 1,3,5,7,9 and then the ray gun returns to the top and displays the even lines, 2,4,6,8,10 etc. By doing this, shots with motion in them appear to split apart when viewed on a progressive monitor. On an interlace monitor or television, they normally look fine, but they have a “REAL LIFE” quality to them. At least that’s the interpretation our brain gives us based on years of watching news as “real” and films as “magic” if you will. It’s conditioning really that has lead us to this stage. The point being, that if you want a film-like image, you need to either shoot progressive, or de-interlace your footage to appear progressive.

In 2002, Panasonic Announced the DVX100 and the SDX900, two low priced video cameras capable of shooting 24 frames per second, Progressive. I was set to direct a feature film in just a few months and really wanted to use these cameras. They were not however due out until wel after our shoot dates. I contacted Jan (Panasonic’s Famous Rep) about getting prototype cameras to shoot my feature film, but she informed me there would not be prototypes available before my shoot date, so we were left with our only budgetary option; shoot on widescreen DVCAM with a Sony D35WS. I could have shot on my XL1, but I wanted widescreen and the best image I could get. The XL1 does not have a true widescreen, and does not have a lot of resolution either.

I knew for a film, I HAD to have widescreen. There was no question about it. If I could have shot progressive as well, that would have been even better, but we were stuck shooting interlace. The Sony F900 and Varicam were not in our price range.

So, in post, I knew I would have to DE-INTERLACE the image, basically throwing out some resolution. But the “LOOK” of the piece would be overall more film-like.

In post, I captured in DV, and used Nattress G Film Effects by Graeme Nattress. (Graeme is now working on the RED codec and software, plus other great plug-ins.)

I choose to de-interlace the image and create a 30P presentation of the movie. As of the last few weeks, I’ve been preparing a final DVD for the distributor and have really been unhappy with the results. Most of the movie looks fine, but there are a few places where the DV compression and the interlace jump out and ruin the picture.

The first thing that caught my attention was the DV Compression. I have recently been editing using an uncompressed codec with an AJA Kona board. So, going back and looking for DV artifacts I found them all over the place. Most notably in this shot.

The pink shirt exacerbates the problem creating blocks of color.

To solve this problem, I decided to re-capture the entire movie as uncompressed using my Decklink HD pro capture card and a DSR-2000 DVCAM deck with SDI out. The strange thing is, the Tape format is DV, yet capturing uncompressed makes a HUGE quality difference. Notice on the shots below of that same image:

Notice just how blocky the shirt is on the DV file to the left and how much less blocky the uncompressed images is on the right.

This is off of the same DVCAM tape. Those people that say editing DV natively over firewire is just like editing uncompressed are wrong. There is a huge difference in quality. Capturing uncompressed solved a lot of my problems with those troubling images. There was still something bothering me about the images. For one thing, which is a whole new can of worms, the Saturation, color, and contrast was a lot better in the uncompressed files. The DV files were washed out in comparison, which of course, means I have to re-color correct the entire movie. This time, I’m going to do it on Color rather than in the Nattress Filter. I think I can achieve the same result and gets me valuable experience with Apple Color. But even though the uncompressed codec was better, it’s still an NTSC codec, which means that it’s interlaced.

This was the strangest part of this process for me. When I de-interlace the images, they look right in Final Cut, but when I export them out either as a stand-alone file through compressor, or directly through compressor, my images had interlace RE-introduced to them. My guess, is that on export, it conforms to the codec you are using. I searched Final Cut for a way to make the coded progressive, but could not find a way to do it, and maintain the NTSC settings. There are ways to do HD using uncompressed and progressive, but not NTSC.

The moving titles int he beginning of the film, really show interlace, and in fact even after de-interlacing them, they still show up as interlaced in Final Cut and they look even worse when exported.

So, my next option was to find a progressive codec. I found this in Apple’s ProRes codec. There is a check box to enable interlace. So duplicated my uncompressed sequence and chose ProRes HQ as the codec. After a render, this resulted in AWESOME looking progressive images.

Notice how the moving title in the lower right corner is completely interlaced as it moves. Also, the static title is not very crisp, even at Uncompressed SD resolution. It does look better on an NTSC monitor rather than the canvas display on a computer.

Here you see the ProRes version, with a lower bit rate, but the titles are crisp and there is no interlace in the actual titles.

Using ProRes throughout the chain to DVD, results in solid images and titles and a really pleasing end product. I have not yet attempted to go through Color, yet to know if it retains the ProRes Codec or reverts each clip back to uncompressed, but I’m bound to find out this week.

I’ll be doing a lot more work in ProRes in the future. I do like DVCproHD as a codec, which my camera shoot natively and I can edit on the fly, but ProRes really is a nice codec. It’s the Interlace that really makes images look bad. If you can, shoot progressive. If that is not an option, de-interlace, but find a codec that will be progressive. ProRes is not available on windows, or on mac without a Final Cut Studio Install. There are some great 3rd party codecs out there, such as Cineform, so check those out when you are looking for a codec.

Thomas A. Koch