Super extra spoilerific video of spoilers

If you take some high resolution shots of the heads in the drum we could make more supposition, but my first guess is that Sony just put really small heads on this relative to "cheap" VCRs, so it can align them more precisely with the tape.

Aaron the Tinkerer

Is this not a function of Time Base Correction? I've seen this functionality before in television broadcast linear tape editors where you could jog through frames at various rates and get very clear stills so you could set your in and out markers for editing. <a href="https://en.wikipedia.org/wiki/Time_base_correction" rel="nofollow noopener" target="_blank">https://en.wikipedia.org/wiki/Time_base_correction</a>

Kajico

What an interesting device. It looks like it’s got *really* precise tracking of individual frames. Seems like the pinnacle of the technology. The stepping action reminds me of the vacuum tape drives on early mainframes like the IBM 701. (Where the vacuum was there to reduce the chance of snapping the tape, which presumably here is done with careful control of tape pressure.) Really liking this crowdsourcing of “how does it work”! Ewen

Ewen McNeill

So Wikipedia says audio is recorded on the edges of the tape from a separate head, so it makes sense that it has to move continuously when reading that. the only thing I can think of with my rudimentary knowledge of VHS is that the head is going over the same track when stationary, completing the other part of it's rotation during vertical blanking, and reacquiring the track to make another pass. When it moves, it would then advance the tape during vertical blanking to pick up the next frame seamlessly. So when you touch the head, it throws the timing out the window and can no longer get clean passes, and when you play audio it goes to continuous slow advance and then maybe skips video fields to keep the timing correct.

Well, all I can tell you is that my father had a Sony SLV-715 in the 90s and it behaved a lot like the VCR in this video. Freeze frame was perfect and you could also hear that stepping sound in slow motion. But that one was marketed as a 7-head VCR. The 7th head was a "flying erase head". You could also cut out commercials by pausing the recording when the commercials started, then skip frame by frame to the exact moment (last frame of the movie before commercials) and start the recording when the movie continued. The commercial break was often invisible (depending on the scene and if they repeated a few seconds after the break) when you watched it later.

Robert

Thanks for actually trying to get the details like this right! I love Technology Connections exactly because it doesn't do the popular science thing where as soon as something threatens to go in-depth, they handwave 'ah, because of piezos or something' without actually having done their research. Technology Connections is different in that, and I'm glad I could help there.

Sprite_tm

If you say it loud enough you'll always sound preco...ciers

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