Help on a topic--Don't read this if you want to avoid spoilers

You may be interested to know that vhs editing decks could replace a single video frame - 2 rasters - with no erasure noise.

Dave Mausner

The ribbon cable from the drum has 7 pins from what I can tell. There were 10 traces in the cable, but that was a trick! There are only 7 contact pads going onto the board.

Technology Connections

And now I realize I'm a dumb. The Betamovie had one head that was two. So this has two heads that are four.

Technology Connections

Thjat is the one indeed. It was a bit hard to make out, but at least on one side, I saw four wires to the little PCB, indicating two heads there. On the other side, I only saw two... either the camera didn't pick up on it, or the head actually is a four-head assembly which is made cheaper by only winding three heads. Would be nice to know the wiring between the drum and the PCB; it may be possible to figure out more from there.

Sprite_tm

Ho ho! Maybe that's all it is. Was that eBay listing for something like $225? 'Cause I think I've seen that. If you think this could simply be a 4-head VCR then perhaps that explains it. It's still the best damn still frame I've ever seen. I'm uploading a video right now that shows it a bit.

Technology Connections

Aw, Patreon ate my comment, possibly because I included a link to eBay which had a better view of the head... My point was that this may actually be a 3- or 4-head VCR, without fancy dynamic tracking. See <a href="http://www.ronaldsnoeck.com/vcr.htm" rel="nofollow noopener" target="_blank">http://www.ronaldsnoeck.com/vcr.htm</a> for the details: these heads are very close together and can do a perfect 'trick' still frame. I conclude that from the fact that the head assembly seems to have 4 coil connections (4x2pins) and that there's nothing on the PCB indicating piezo shenanigans.

Sprite_tm

There were many models of time-lapse VCRs using standard VHS cassettes, as well as recommendations for when to discard used tapes based on how many recordings were done and at which speed.

Technology Connections

Alec, while it works perfectly on any video tape security recorders used a special tape as most used a 30min loop tape that is formulated for continuous rewriting on the magnetic media, normal vhs tapes eventually degrade over time provide a much poorer quality playback of the recorded video. After successive erase and write cycles, Analogue DVR’s tapes will continue to produce good quality after high cycles, whereas normal tapes it depends on the brand. As I work in the security industry this was something we had to be mindful of thankfully when I do my apprenticeship these units had nearly been completely phased out.

Paul Fisher

As far as I can tell it's not doing that. I can only feel movement in the capstan when it advances to the next frame.

Technology Connections

Thank you for this! This helps answer another question... albeit an unrelated one. I've only tried one other VCR, but it was able to play back time-lapse tapes perfectly. I just can't see how a two-head VCR can make such a good still-frame unless it's got something magic in its heads. I could be completely wrong, though.

Technology Connections

Sorry about that... I fixed the link

Linh Pham

The colon at the end of the URL needs to be removed for the link to work.

Microfrost

That makes sense...I wonder if the still frame problems could be solved by moving the tape slightly back-and-forth over the heads during pause...would that not correct for the "still tape" issue? And, yes, I realize it would prematurely wear the tape.

Per <a href="https://pro.sony/s3/cms-static-content/operation-manual/3193023022.pdf" rel="nofollow noopener" target="_blank">https://pro.sony/s3/cms-static-content/operation-manual/3193023022.pdf</a>: "The format used for time lapse recording in this video cassette recorder differs from the regular S-VHS and VHS video formats. Cassettes recorded in three-hour mode on this unit can be viewed on a normal S-VHS or VHS video cassette recorder. However, cassettes recorded in other modes may show some picture noise when played on a normal... video cassette recorder."

Linh Pham

It's not progressive, though. A test recording from some PlayStation 2 FMV footage at 30P yielded a repeated frame with each advancement. A home video recorded in 60i didn't do this. And... I may be showing ignorance here but I thought the interference wasn't due to the fact that it's interlaced per se, but simply that without the movement of the tape, the angle of the head as it passes it becomes slightly off, and you get crosstalk between the bands. It starts the sweep on target and drifts off, because in normal operation the tape would move .5mm to the right *while* it's making that sweep. If you could follow the track using a piezo element on the head, then the misaligned angle from a stationary tape could be corrected.

Technology Connections

Sorry, I meant to say that the fields came from the same frame, as opposed to progressive scan (so lines 1/3/5 are drawn then 2/4/6). It's definitely a mode I saw in PAL VHS for security cameras, but I admit ignorance of how it actually worked. Good luck!

This machine not an SVHS model (that was the SVT-3050P) and it's been my understanding that the snow bars appear because with the tape stationary, the heads sweep across the tracks at a slightly incorrect angle so it starts to lose the signal. Plus, it's not scanning progressively. A test tape from a 30 FPS recording produced two more or less identical frames in a row when played back in time-lapse mode. So it is recording one field at a time.

Technology Connections

There seem to be at least a handful of VCR repair shops near Chicago. One of them might have a tech that knows something about this. Calling Sony probably won't get you anywhere, but you never know. I had a question about a decades-old Peavey sound mixer. I called them, and they swore they'd never heard of or made the device in question. They kept transferring me to people who had been there longer and longer, and eventually, I got to the old timer that actually designed the thing.

Microfrost

This leads me to believe that the recorder must be using a progressive scan variable frame rate (always locked to 50 or 60 or 25 or 30 Hz or whatever standard you'd prefer) to record video. progressive scan would remove the interlaced issues that would cause a problem when displaying still frames.

When it's recording in all speeds slower than 24 hours (and playing back in anything but normal SP speed) the tape is simply advanced one step per frame. Then it is held there until the next frame. The head drum spins like any other VCR. And it doesn't matter at all at what speed it was recorded. It can be perfectly played back at whatever speed you like (which is simply more steps per second).

Technology Connections

To clarify, the shimmer you get on VHS when a frame is frozen is because the picture is drawn of two fields, and the second field is at a 60th (or 50th) of a second later. By writing a full frame in progressive scan, reading both fields and displaying them would not give the shimmer.

I appreciate that you reach out for help to make sure that you get the best research possible. Stupid question: the product page for the head appears to be here: <a href="https://www.tlselectronics.com/TLS/product/2N4N-Q.html" rel="nofollow noopener" target="_blank">https://www.tlselectronics.com/TLS/product/2N4N-Q.html</a> Have you tried just asking the manufacturer for documentation? It's not like your viewers are going to try to undercut them, so it could make for good PR.

John Mertz

It looks like it is recording slower according to this: <a href="http://pdf.textfiles.com/manuals/STARINMANUALS/Sony%20Security/Archive/1999%20Catalog%20-%20Surveillance%20VCR.pdf" rel="nofollow noopener" target="_blank">http://pdf.textfiles.com/manuals/STARINMANUALS/Sony%20Security/Archive/1999%20Catalog%20-%20Surveillance%20VCR.pdf</a> "The longer the recording time, the fewer the number of pictures recorded per second on the tape."

If I remember correctly, SVHS had more lines available than both VHS and NTSC, so I imagine rather than storing a 240 line field at a time, in frame mode it would just write the entire frame at once.

So yeah, that would be my next question...Is the tape moving across the heads at a normal speed? I'm trying to wrap my head around how one could construct a time-lapse vcr without somehow radically changing the format for replay/review

It's not using a frame buffer of any kind--disturbing the head drum disturbs the image, too. Furthermore, it doesn't record in steps during the 12 and 24 hours modes so that it can record audio, and to play these back with audio the image quality is reduced. I think it can't continuously follow the tracks with the tape in motion, as turning the audio off puts it back into stepping mode, and the image quality goes back to perfect. Gut tells me one sweep analyzes the track, the next sweep follows it. But that can't work if the tape is continuously moving. (or something) I'll post some pictures in a sec

Technology Connections

So, "it's *not* using a digital frame buffer." Could it be using an analog frame buffer? Analog "bucket brigade" ICs were used to make analog audio delays...Ampex made fixed-platter disc-based video recorders to create slo-mo and instant replay. Could you post some photos of the recorder's circuit boards? I would enjoy examining this also.