How were the special effects achieved for the Kraftwerk Die Roboter 1978 music video?

Question

The following video for Kraftwerk's Die Roboter is very interesting because it features some effects which I think might require a framebuffer to achieve. Having a framebuffer in 1978 would to my knowledge be a very big deal.

I'm interested in how the following effects were achieved:

1. First of all we see vertical mirroring of the video multiple times such as at 04:20 in the video. What's interesting is when the effect is enabled you can see a drop in resolution. This makes me suspect that it could have been an early digital framebuffer that helped with this effect. I'm not sure how else it could have been done.
   
   ^{Click to enlarge}
   Same test with original video

   What's interesting about this is how perfect the mirroring is. I took the top half of the image and vertically flipped it using GIMP. I then moved it down in difference mode until I lined it up. Given that some people were talking about things such a recording studio monitors or using an actual mirror I was surprised how perfect the mirroring effect is.
   
   ^{Click to enlarge}

2. At 3:02 we can see what looks like standard video that's been slowed down. What you'll notice about this part of the video is that the vertical resolution has been halved. Did they use a framebuffer for this or maybe it's possible with a professional video tape recorder to play the same fields multiple times and then use it for both the odd and even fields?
   
   ^{Click to enlarge}

3. At 04:49 you can see horizontal mirroring. This one would just need a line buffer but is that how they did it?
   
   ^{Click to enlarge}

Answer 1

All of these effects are being created using beam splitters to combine two images of the original recording.

The lower resolution is a product of the second image, the lower in the horizontal split for instance, being viewed through a mirror and splitter. A single tape of the original recording is played on a studio monitor, with one side of the splitter aimed directly at it, in this case, the upper image. The second, lower, image has to be presented to the side of the splitter, and this is arranged with mirrors. This leads not only to a (tiny) loss of resolution but other optical effects due to phase differences and timing due to the longer optical path.

The reason for this seemingly over-complicated system, as opposed to two monitors firing at the splitter, is that one has to be reversed, genlocked and phase adjusted. The former are easy enough, but the latter not quite so much.

Most studios already had a beam splitter system for titling or (more rarely) stereoscopic recordings. In the latter case, the two lenses are both facing forward so one has to be turned through 90 degrees to enter the splitter from the side, so most used additional optics to try to make the two paths optically equal. Using two separate recordings rarely worked out well, in contrast to film where the resolution was high enough for this to work. Titling doesn't really need this complexity due to the high contrast, but to the modern eye the softness of the results are obvious, including in this video.

Answer 2

It may be helpful to note that this is not a live recording but a pre produced video. These are pretty standard analogue (post production) effects at the time. Including real mirrors, two cameras and insertions. The only digital effect here is the text.

German TV, foremost progressive music shows, of the 1970s was notorious for using cutting edge technology. A sound financial base is one of the advancements of public TV :)

Answer 3

Analog techniques of delaying a video signal would have been commonplace by the late 1970s. In fact, I think every color SECAM television set would have needed to include an analog delay that was one scan line long. Conversion between 25 and "30" frame per second video would have required a piece of equipment with hundreds of carefully calibrated delay lines of different lengths, along with circuitry that could switch among them seamlessly. While effects such as described may have been produced optically, technology existed that would have been adaptable to perform such effects directly with an analog video signal.

Speeding up, slowing down, or time-reversal of video playback would have required either transcribing to film or using a video disk system. Such a system was used in the Doctor Who story "Robot" in 1974.

I don't know when frame-buffer-based video manipulation systems started to be available, but a rather powerful one was used in the Doctor Who story "The Leisure Hive", which was broadcast in 1980.

Answer 4

Two things to note:

1. The linked-to video is a "remastered" version that has been upsampled to 1080p and cleaned up. How much of what's visible on-screen is original and how much is interpretation by the remasterer is debatable (though it doesn't look like the remastering affected anything you asked about). Compare the following shots of the same frame. The first is the remastered version and the second is (as best I can tell) from the original tape:

Remastered	Original
Source: Youtube / RemasteredMemories	Source: Youtube / TecnopopEspaña

2. The pixelization visible in that shot is likely due to the raw footage having been shot using interlaced video. To get a clean freeze-frame image one has to double each scan line¹. As an example, here's an interlaced shot of a car wheel in motion that has been produced by instead simply merging successive frames; the "combing" artifacts are obvious:

^{Source: Wikipedia / Mikus}

¹ At least with 1970's technology. One can do image processing to attempt to combine the two time-offset frames but even with today's technology it's difficult to do good-looking de-interlacing.