Dealing with interlaced video.

Digitizing old video sources (stuff made in the 20th century) is a hassle for multiple reasons. Probably the biggest is that old video was stored in an interlaced format. This Wikipedia article digs into the details about interlaced video, but the short version is interlaced video is captured and stored as half-frames instead of full frames, and combining those half-frames for playback on modern displays (which are almost all progressive instead of interlaced) can get messy.

This is true for material that originated as video, and it’s also true of material that originated as motion picture film. The film-to-interlaced-video process often involved a hack known as three-two pulldown. That hack was necessary because of differences between motion picture film frame rates and video frame rates.

Adding to the hassle of dealing with old video material is the fact that modern video editing software (stuff like Adobe Photoshop and DaVinci Resolve) just “fixes” the interlacing behind the scenes. I guess this is OK if you aren’t picky about your video conversions, but I am picky about my video conversions.

Enter Handbrake. Handbrake is a Mac/Windows/Linux app that was originally known for its ability to rip DVDs. This was back in the early-2000s when most computers had a built-in DVD drive.

Most modern computers don’t have a DVD player, and the modern version of Handbrake won’t even rip a DVD if your computer does have a DVD player. But these days Handbrake is a good app for converting digital video from one format to another. And Handbrake is very good at dealing with interlaced video.

For video with motion picture film origins that is recorded at 29.97 frames per second (it’s not quite 30 fps because reasons), Handbrake has a detelecine filter. So, basically, you set your output frame rate to 23.976 fps (not quite 24 because the source is not quite 30), set the Detelecine filter to Default, and set Interlace Detection to Default and Deinterlace to Decomb. The interlace detection/deinterlace filter will help clean up any errant frames that don’t conform to the usual three-two pulldown cadence for whatever reason.

For video with 29.97 interlaced frames per second origins, you can set Deinterlace to Bwdif or Yadif and Preset to Bob. Then set the output Framerate to 59.94 fps. (Yes, that’s not quite 60 fps.) I am not exactly sure what Bwdif and Yadif mean. But they’re doing some kind of magic and taking each of your video’s original half-frames and scaling them up to full frames. And since each half-frame is becoming a full frame, you now have (almost) 60 frames per second instead of (almost) 30. From what I’ve read, Bwdif is a little better and slower than Yadif. Since I’m usually not in a rush when I am doing video renders, I go with Bwdif.

The Bwdif/Yadif is a good approach for mixed source 29.97 fps video, too — stuff that includes both video-sourced footage and film-sourced footage. I’ve only tested this with a couple of things, but it seems to work well so far. If you’d like to see for yourself, you can download a little test video I made. This is the first thirty seconds of an extra from a Jonny Quest DVD. It includes animation (originally produced on film) and talking-head interview segments (from interlaced video recordings). In the finished video, the animation plays in a three-two cadence (one film frame for three video frames, the next film frame for two video frames, etc.), and the video clips play back at (almost) 60 frames per second, with each original video field blown up to a full progressive video frame.

If you want to get really nerdy, you can step through the sample video one frame at a time and see how the animation moves versus how the live-action interview footage moves. It’s not perfect, but it’s pretty good considering the limitations of the source material.

One more nerdy note. There is a deinterlacer called QTGMC that is apparently even better than Bwdif. But I looked into installing it and… it’s a lot. It looks like, for starters, I’d have to get an app called AviSynth and then install a bunch of plug-ins. I appreciate that with Handbrake, you just download it and it works. But if you want to read more about QTGMC and how it compares with other deinterlacers, maybe start with this blog post from Andrew Swan.