Answerman

Why Is Old Anime Still Released In Interlaced Format?

Anonymous asks:

Why is it that older shows are still presented in interlaced form on new-release DVDs? They look terrible on a computer.

Prior to HD video being a thing, all video was interlaced. All of it. Every show that was mastered in standard definition is stored in an interlaced format. This is at odds with how many of us consume video today. A nice current television set or video projector will be able to display interlaced video just fine, and in many cases it's hard to tell the difference between an interlaced and progressive image. A computer, however, tends to show all the gross combing artifacts left behind by having the image be made up of two alternating fields of image.

Video was designed this way because early CRTs couldn't refresh their screen fast enough. CRTs work by shooting electrons a horizontal line at a time at a phosphorous screen, which would glow for a fraction of a second (certain colors glow for longer). For each frame, the electron gun would "draw" a line, zip back to the other side, draw another line, and zip back. The problem was, the phosphorous at the top of the screen would lose its glow by the time the electron gun got to the bottom. So, early developers of television would have the gun draw every other line, zip back to the top, and then fill in the opposite lines. These two complete interlaced images were called "fields", and together they made up a single frame of video. CRTs improved a lot as time went on, but all pre-HD video was built on these foundations.

This brought about another problem: movies, most TV shows, and certainly all animation was produced on film, which looked far better than analog video. And film was made at 24 frames per second, as opposed to (North America and Japan's) 30. If you just projected a film image and photographed it with a video camera, the different frame rates would result in a really ugly flicker effect. And so, engineers invented a device called a "telecine," which would spread out every other film frame for an extra field of video. Early telecine devices were essentially just a modified film projector with a special lens that fed directly into a camera sensor and a few tweaks to its mechanism so it would flicker less.

Early telecines used vacuum tubes, just like video cameras of the day did. In the mid 1980s, the CCD (Charge Coupled Device) was invented -- the digital sensor used in cameras to this day. This made for a much sharper image from both cameras and telecines. (Today the telecine is completely obsolete -- now to capture film to video we use a digital scanner, which slowly scans every frame of video separately and reassembles the final video in a computer.) The transfer from film to video was an essential step in the production of every anime that was shot on film. However, where in the process this took place varied a lot: movies were transferred as a final step, to produce master tapes for home video and television broadcast. OVAs were often transferred from raw footage, and had editing and other things added on video. TV shows usually worked like movies (but taking a lot of low-budget shortcuts on the film end of things).

Nowadays, HDTVs are made to work with "progressive" video (the whole image at once, same as film), and so are computers. And while most HDTVs look pretty good at showing interlaced video, computers are generally pretty terrible at it. But now we're stuck with decades of anime masters that are interlaced. What do we do with those? Discerning fans prefer progressive-encded DVDs and Blu-rays, and streaming services like Hulu won't even TAKE interlaced video.

Obviously the best solution is to do a brand new, high quality digital scan of the old film elements, but that's not always possible -- a lot of old film elements were lost over the years, and with some shows doing a new scan would be completely cost prohibitive. (This is especially true of OVAs, since the entire show might basically have to be re-edited.) So, if we're stuck with the already existing masters, it MIGHT be possible to extract the film's original 24 frames per second of perfectly progressive video. That process, by which the interlaced fields are compared, the pattern by which the extra fields were added is found, and the duplicate fields are thrown away -- resulting in a perfect 24p image again -- is called Inverse Telecine, or IVTC. A lot of video encoding software has this built in.

There are a number of problems with this. The first is that most IVTC features are built with live action in mind. Anime doesn't use every frame of film -- in fact, it often repeats same image for 2 or 3 frames (or sometimes more!), due to its inherently limited animation. That confuses the hell out of a lot of IVTC software, which then freaks out and delivers an unusable result. There is a trick to IVTC'ing anime, but not a whole lot of people know how to do it.

But the bigger problem is that the telecine on many shows weren't done in a way that IVTC is possible at all. Anything transferred with an ancient tube telecine (which were used by some studios well into the 90s) smears one film frame into the next, making restoring the original 24p images impossible. Even after digital telecines came out, many of them didn't cleanly match film frames to a set number of fields -- it just sort of blended the film into approximately the right number of video frames. There is no way to reassemble these frames in a way that will restore the original images.

The only other way to get a progressive image from a hopelessly interlaced master like this is to use various software methods to blend the fields together. Some methods look better than others, but there's basically no way to do this without further damaging the image. Inevitably some frames get blended into each other, and occasionally you get a few frames where the interlacing is still visible. Some out-of-phase masters end up with a weird effect where the top half of the screen is one frame ahead of the bottom half. It looks terrible!

There's a whole 'nother issue where something is animated in 24p, and then edited onto interlaced masters, at which point video effects are added as interlaced 30-frame video. Sometimes these are scrolling credits, fades, special effects, and even whole cuts of CG that are just not intended to be 24p like the rest of the animation. There's nothing you can do but blend those frames together, or ignore a field and end up with a jaggy looking, half-resolution image. There is no good solution. This problem still sometimes happens today with newly produced anime (though it's getting quite rare thankfully).

Faced with an anime that just can't be made progressive in a way that looks good (or good enough -- it's always a judgement call), publishers have no choice but to keep the video interlaced and encode a disc like that. The show will likely never be made available on streaming services (although Crunchyroll will put up with some frame blending if that's all that's available). The disc might not look great on a computer, but it will still look decent on a television. And that's about the best that a publisher can do with a show like that.

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Anime News Network founder Justin Sevakis wrote Answerman between July 2013 and August 2019, and had over 20 years of experience in the anime business at the time. These days, he's the owner of the video production company MediaOCD, where he produces many anime Blu-rays. You can follow him on Twitter at @worldofcrap.