Is Frame Interpolation Important?

Is Frame Interpolation Important?

Evan Powell, January 20, 2009

In the past four months we've seen several new 1080p projectors released with a feature known generically as frame interpolation. The new Epson 7500UB and 6500UB have it, as does the Sanyo Z3000 and the Panasonic AE3000. Epson calls it FineFrame, Sanyo calls it Smooth Motion, and Panasonic calls it Frame Creation. But it is all the same concept: the projector evaluates the differences between individual frames of film or video, and creates interim frames to be inserted between the real frames in the source. The objective is to reduce motion judder and provide a cleaner, more artifact-free viewing of film and video material.

Two complaints have been circulating about frame interpolation technology. One is that it can make a movie look more like digital video, something which people are calling, somewhat derisively, the Soap Opera effect. In essence, the complaint is that it makes a film, which has a slightly surreal and sensual quality, look like a CNN Situation Room HD broadcast, which by comparison is hard, cold, clear, and real (sometimes disturbingly real). When James Bond begins to look like Wolf Blitzer, you know you have a problem.

The second complaint is that, while frame interpolation can reduce or eliminate much of the film judder we see in movies, it sometimes introduces other artifacts which may be just as problematic. For example, instead of the judder, we may see some ghosting as subjects move across the screen, or some unnatural disintegration of the picture during momentary fast pans of the camera.

These complaints are well-founded. Some frame interpolation systems do indeed produce these undesirable side effects. But if it is done well, the picture can be virtually free of artifacts while it retains that mystical film quality. Ideally, what you will see is a clean, stable, but still filmlike image that many will find irresistibly engaging.

Not All Frame Interpolation Systems are Created Equal

We've said this before and we cannot emphasize it enough: Don't make the mistake of seeing a frame interpolation demo on a particular video product and assume you've seen what it will look like on all video systems. Each vendor approaches it differently. They use different algorithms to generate the interim frames. Some products generate more created frames than others. These differences cause the type and frequency of artifacts to vary from product to product.

In addition, the digital video look which people want to avoid in traditional movie viewing, varies greatly from product to product. It tends to be more exaggerated on smaller screens than on larger ones. If you are projecting a 60" diagonal image, the effect will be more obvious than if you use that same projector to throw a 120" image. The digital video effect can sometimes be more obvious and distracting on plasmas and LCD TVs than it is on the projectors we've seen.

When to use Frame Interpolation

Among the 1080p projectors that have frame interpolation, the Epson 6500 UB produce a more obvious digital video effect than do either the Panasonic AE3000 or the Sanyo Z3000. Thus, we would not use the 6500 UB's frame interpolation when viewing regular movies. However, this does not mean that it has no application. For example, if you happen to be a fan of animated films, the digital video effect is irrelevant. The Pixar movie Cars has a reasonable amount of judder and flicker when played at 1080p/24. But when you engage the frame interpolation system on the Epson 6500UB, it has nothing but a beneficial effect on the image. The picture is smoother and more stable. There is no soap opera effect to be concerned about since animated films are obviously not real. Frame interpolation can be beneficial for all animated films, from Toy Story to Shrek to Finding Nemo to Ratatouille.

If you watch a lot of sports in HD on channels broadcasting in 1080i, you may find frame interpolation particularly attractive. For whatever soap opera effects are present in the video system you have, they are irrelevant in sports--you want that maximum reality effect. Of course, Fox Sports, ESPN, and ABC all broadcast in 60p format, so frame interpolation is not needed. But with sports broadcasts in 1080i, it can help.

Similarly, music concerts on HD discs may be enhanced with frame interpolation. Again, if there is any soap opera effect, it is a good thing--you want the Eagles Farewell 1 Tour to look as real as possible. It looks amazing in HD DVD, and hopefully they will release it in Blu-ray one of these days.

In the end, even if the frame interpolation system on your projector does have a particularly exaggerated digital video effect, this can work to your advantage in sports, music concerts, and animated films. You can always turn it off if you don't care for what it does to your traditional movies.

When it comes to traditional films, the digital video effect can be disturbing. We find that the Epson 6500UB produces a noticeably greater degree of undesirable "reality" than do either the Panny AE3000 or the Sanyo Z3000. Furthermore, on the Epson 6500UB there are occasional ghosting artifacts and other oddities. We don't see these nearly as frequently on either the Sanyo or the Panasonic projectors. For these reasons we consider the Epson implementation of frame interpolation, at least in its current iteration, to be the least successful of the three.

Conversely, the Panasonic AE3000 has the most robust and powerful frame creation engine that has appeared so far. When dealing with a 1080p/24 source, it generates three interim frames for every real frame, and plays them back at 96 Hz. (Panasonic is the only projector vendor that does this so far; both Epson and Sanyo generate one interim frame for each real frame.) In addition, there are two settings for Frame Creation on the AE3000--Mode 1 and Mode 2. Mode 1 evaluates the movement between two successive frames to generate its interim frames, and Mode 2 evaluates the movement between three successive frames. Mode 2 is clearly superior in its results, and again, neither Epson nor Sanyo have this capability.

Panasonic developed their own proprietary algorithms for Frame Creation in house. The result is an extremely smooth and artifact-free display of film. And in addition, the digital video effect is remarkably subtle in comparison to the Epson 6500UB. When the AE3000 is projected onto a 120" screen, the image looks like very clean film, not an ultra-real CNN HD video broadcast.

Is Frame Interpolation Important for You?

Well, only you can decide that. Personally, I am distracted by motion judder when I see it on the large screen. I was never bothered by it when watching a 42" plasma TV because the image was too small and the artifacts were less obvious. But at 120", the viewing experience is more immersive, and motion instability can be quite annoying. I'd rather have those artifacts gone if I have the option. So I am elated that vendors are now beginning to tackle this problem.

However, having said that, I should also say that motion judder is not a problem in all films. For example, the new release of Thunderball in Blu-ray has very little judder. The script is bad and the acting is worse, but at least the cinematographer knew what he was doing. In this film there is very little camera panning, and when the camera does pan, it almost always moves slowly enough to avoid the introduction of judder. You can watch this film in its entirety in native 24p and see almost no judder at all, which is rather remarkable. If you happen to be watching movies that were filmed in this manner, frame interpolation has no benefit.

On the other hand, the new Casino Royale Blu-ray, while it is a much better movie, is not nearly as successful in this particular regard. Moderate speed camera panning is rather frequent in this film, so you see a lot more judder. But it's great for us. We use a number of scenes in this film to exercise the various frame interpolation systems on the projectors that have come out so far.

And by the way, contrary to what one might assume, motion judder is not a problem that is limited to action movies. We've mentioned the film Swimming Pool on occasion before. This is an example of a very slow paced movie with no action whatsoever, and yet it is full of motion judder. It is not the amount of action in a film that produces motion artifacts, but rather the way the cinematographer handles the camera. So don't think that just because you are not watching stuff like 2 Fast 2 Furious that you won't be bothered by motion judder.

In the end, frame interpolation can be used with different types of film and video source material with great success. Sometimes it isn't necessary, and sometimes it helps enormously. Some frame interpolation systems are clearly more comprehensive than others, so as they say, your results may vary. We are extremely supportive of this new enhancement to video processing. Our hats are off to Panasonic in particular for showing how powerful the technology can be. We hope all vendors will give serious consideration to including it in their next generation video projectors.

(09/21/17 - 09:44 PM PST)
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