VHD decode project

[ppppenguin]

I've just been told about this project to recover old VHS tapes. It uses a special purpose data acquisition system to take the RF from after the head amplifier and save it on a PC:

https://hackaday.com/2022/12/13/vhs-deco...l-efforts/

It uses hardware developed for the Domesday Duplicator project that recovers full information from the BBC Domesday Project discs.
https://github.com/simoninns/DomesdayDup...i/Overview
Seems to be a lot cheaper than a high speed analogue DAQ (data acquisition system) or suitable SDR (software defined radio)

This method could be used to recover pictures from any videotape format, provided there is a machine capable of replaying the tape. Equally applicable to 405.

[Mike Watterson]

Now if you could read the tapes without a player, as is possible with pressed audio discs?

Is the idea that somehow this is better quality than the player's video out followed by a digitiser? Though I imagine that is possible, but you'd need good heads and existing analogue servo loop working unless it can control the drum and capstan. Then there is tape tension on old worn machines. I was involved in service / repair of N1500, N1700, EIAJ reel, EIAJ cartridge, U-matic, VHS and Betamax in the late 1970s. I suppose if you had an EIAJ 1/2" tape and only a mono player this system could digitise the colour. Some EIAJ player/recorders could even take a retrofit adaptor. I think the carrier was moved to about 800 kHz, no matter if PAL or NTSC, which is why there were Monitors with 4.433 NTSC, which is what you got playing NTSC tapes on PAL EIAJ or VHS. Maybe Betamax and U-Matic too, but I don't remember.

I'd not have thought it could manage any format the player can't play?

I think Betamax drives and cassettes were being used for multitrack digital audio by the time the BBC Domesday started. They made the PCM look like a video signal. Sort of NiCAM without any video. Perhaps would have been a better choice than Laserdisc.

Off topic but:
https://en.wikipedia.org/wiki/BBC_Domesday_Project
Seems to have been started before affordable technology existed. Anyone expert in 1982-1984 surely knew it was a daft decision due to cost and issues with laser disc. I saw laserdisc not long after launch (1978), maybe in 1979 and thought it was doomed. A worse decision than restarting 405 line in 1946 rather than work on 625 line.

One of the first products to be made available to the public on CD-ROM was the Grolier Academic Encyclopedia, presented at the Microsoft CD-ROM Conference in March 1986. You can still buy a brand new USB drive and read 1985 CDs on Mac, Windows and Linux.

Also reminds me of DAB. Now turned off in Ireland, I think, since May 2001 and Lidl still regularly selling DAB radios here (Currys do too).

[ppppenguin]

The VTR has to be able to read the tracks on the tape so it needs to be the same format and in good condition. The EIAJ case is interesting. Provided that the player's head amplifier is good enough to reproduce everything on the tape the colour should be recoverable on a mono machine.

There is the almost practical possibility of reading the flux directly from the tape to make a universal magnetic tape reader. Edivue fluid (carbonyl iron suspended in a solvent) was used in the early days of 2" VTRs to make the tracks visible. This allowed physical editing with a Smith microscope. http://www.vtoldboys.com/editingmuseum/smith.htm I'm pretty sure we have one at the BECG. I know we'll be getting one (another one?) soon. There was also a diaphragm viewer which presumably had fine magnetic particles between two fine diaphragms. I've never seen one. In a crude way these revealed the recorded information. I understand there is a technique that can scan digital tapes, such as old computer tapes. I don't think there is any currently feasible method for analogue tapes.

Both Umatic and Betamax were used for early digital audio recorders. https://www.palsite.com/pcmf1ovi.html As Mike says, they dressed up digital audio to look like analogue video.

All sorts of formats were doomed. Hindsight is a very powerful forecasting tool. To name just a few:

Elcassette - an improved audio cassette

B-Format VTRs - a professional 1" format that was used to a very limited extent. The BECG has a non-working machine

M and M2 Format VTR - professional formats loosely based on VHS. Again they had limited use. Betacam and its variants won that battle. They were loosely based on Betamax. They were the last videotape formats.

CED - a consumer videodisk format.

[Mike Watterson]

Elcaset was about 20 years too late. Actually RCA had a 1/4" cartridge in 1958. The Lear Jet Audio 8 track (1964) came after the compact cassette (1962) and because of the endless loop: no fast forward, rewind impossible, high tape wear and the S/N & frequency response theoretical advantages miniscule in the car. Penetration in USA purely due to Ford and GM including them.

Sony (despite the pocket Journalist cassette before walkman) forgot that part of compact cassette success was the size. High end compact cassette machines were good enough by the time the Elcaset came. The Elcaset portable was only a competitor to Uher and similar. Not for public transport, cycling, jogging etc.
   
The cartridge (from Wikipedia).
   

It wasn't obvious that VHS would beat Betamax, however one of them had to "win". The N1700 was doomed when they came out. The Philips V2000 looked like a possible, but as literally years dragged on (was it manafacturing issues of the piezo mounted moving heads?) it was thought to be already doomed when it did reach the shops.
VHS-C (or whatever it was called) big selling point was an adaptor for a VHS. But size and play time meant it was doomed to lose to 8mm. S-VHS was the last gasp for home tape. Then home recordable CD Video (VCD) and home recordable DVD and Digital 8mm meant Digital VHS was doomed. Digital VHS did exist, but I never saw one.
Mini-disc was crippled by Sony DRM. Too late they brought out a higher quality DRM free version.
Then Flash made Digital 8 obsolete.

I'd think good luck on finding a 1/4 open reel Akai colour video recorder. I saw one once in the BBC. It had been bought out of curiosity. It was terrible. The Super 8 film is better.

The Philips Digital Compact Cassette was amazing but never had even the limited success of minidisc. The head was very innovative and could have led to video tape system without a helical drum. Being able to play ordinary cassettes wasn't good enough, given cost.

[Mike Watterson]

Actually maybe only Ford offered the 8-track, not GM also.

[ppppenguin]

In the early days of VTRs there were all sorts of formats. From the 0.25" Akai, assorted 0.5" formats from Sony CV2000 onwards, an oddball Ikegami 2/3" machine, 0.75" (Umatic), 1" and 2". Apart from Quadruplex there was a 2" helical, the IVC9000. It worked superbly well but saw little use. At 1" there was an early Philips machine (possibly 2 different ones), IVC and Ampex 5000/7000. The last of these morphed into C Format which was the mainstay of broadcasters for years. The 5000/7000 machines got back-named as A Format.

Even in 2" quadruplex there were low-band, high-band and super-high-band machines as tape and technology improved. At least older tapes could be played on later machines.

I dimly remember an article in Practical TV which described many of the formats. Early 1970s? It's on World Radio History but I'm feeling too lazy to dig it out.

I've left out early experimental machines such as the Bing Crosby and VERA, both linear. Also the failed domestic Wesgrove and Telcan which were also linear. I think Polaroid did a "toy" camcorder that used ordinary audio cassettes. It may have a cult following.

[DrStrangelove]

The Fisher Price PXL2000:

https://www.youtube.com/watch?v=TCXJ5twf5tM

[ppppenguin]

Thanks for reminding me. Polaroid did do a movie camera with instant developing but it was way to late and expensive to make any impression.

[Mike Watterson]

Thanks for reminding me. Polaroid did do a movie camera with instant developing but it was way to late and expensive to make any impression.

And Baird had a film to video camera that was developing as you go. Bit of a time delay. But the idea was successful on spy satellites to avoid the "Ice Station Zebra" scenario with dropped film (one was "lost" over northern Norway). Film very much higher resolution than video or ccd stills then. Developed film could be scanned and transmitted in bursts over friendly territory.

I was surprised to see Polaroid cameras and film packs in Harvey Norman on Tuesday, though I'd heard enthusiasts had bought a derelict Polariod plant somewhere (Netherlands?).

The FP camera
https://en.wikipedia.org/wiki/PXL2000
Clever
120 × 90 pixel CCD at 15 fps. Cassette tape runs at x9 speed. The ASIC on playback upscales with a border. I've a €25 GSM phone watch that now does better :D Still, amazing idea for 1987.

[Mark Hennessy]

Mini-disc was crippled by Sony DRM. Too late they brought out a higher quality DRM free version.

Are you sure about this?

The only form of DRM that I'm aware of for MD is SCMS, which was present on all domestic digital audio formats. It permits one digital copy to be made, but not subsequent generations. So perfectly fine for making digital copies of CDs to MDs, for example. You just can't make a digital copy of the MD. Not that you'd want to, because you'd be cascading a lossy data-rate reduction codec that is designed for single-pass use.

SCMS was brought in with DAT in the late 1980s. Not MD-specific - it applies to DCC and CD-R and anything else that has S/PDIF interfaces. It's carried in the channel-status data of the S/PDIF interface - bit 2 is the copyright flag, and bit 15 is the generation flag.

Of course, most people just went via the analogue hole. The quality of ADCs and DACs was more than good enough by the mid-'90s for most content. Or you could find devices that would alter the channel status bits to allow digital dubbing.

Given how very simple SCMS is, there's some debate about whether it even counts as DRM.

I suspect that rather than MD, you could be thinking about their early portable solid-state players, which used various versions of the ATRAC data-rate reduction scheme that MD used. Loading them up with content required the truly horrific (I don't say that lightly!) software that was SonicStage. This used a much more aggressive form of DRM. Fortunately their later players were much more conventional and worked like a standard USB storage device, so no special software required to mange them, and they play a wide range of formats with no need to transcode, and because the files aren't altered by the player, there's no DRM added (I copied off some files from mine to play on a laptop at a hi-fi show once, because someone forgot their HDD. No-one noticed they were hearing MP3s!). I still have my player, but it probably needs a new battery by now. Sony still sell them, including some very expensive versions.

Or possibly NetMD, which also used SonicStage, but copied to MD via USB. The discs would play in later MDLP players. A good idea in many ways, but didn't get much traction. It arrived too late, and not everyone had suitable players. I don't, although I could find one at work if needed.

What caused MD's slow decline was CDR, followed by HDD and solid-state devices. Not really Sony's fault - although they, like many, failed to anticipate just how quickly CDR prices would fall.