Video On Compact Cassette

[19Seventy7]

Hi,

I've been thinking about if video (Albeit very poor quality) could be captured, and replayed on a compact cassette, using a normal cassette deck (and PC software) I've seen those cameras which record onto compact cassette in black and white, which sparked the idea.

I was playing around with the idea and put the video plug of a composite lead into the right channel input of a cassette player and mono audio into the left.

I pressed record on the cassette deck, and both VU meters jumped to life. Left bounced, whereas right stayed relatively still on around 20-40%

I recorded the cassettes data directly to Audacity, and there were two wave forms. I sent the file to a friend who has composite in on their TV and played the audio. The audio played fine, and there was a blue band at the top of their screen.

What would need to be done to get a full video (Monochrome or colour is fine)

I think the frequency would need to be increased, but I'm not too sure. I did try increasing the frequency in audacity, but every time I tried, audacity crashed.


This is only a small project/thought so it doesn't matter if it's do-able or not, although I have seen it done before, in devices made for that purpose.


What are your thoughts on this?


Thanks

[stacman]

Hasn’t techmoan on you tube and the 8 bit guy done something on this?
Regards, Alan.
https://m.youtube.com/watch?v=TCXJ5twf5tM

[Davewantsone]

The sound would be fine. Unfortunately the bandwidth of the video would only be around 10kHz. The line sync pulses are of the order of 15kHz, so the cassette tape would not record that, so you woul not see anything.
The 8 bit guy takes about using an ordinary cassette tape in a video camera. The camera would use helical scan, which would give a tape to head speed around 100x that of an audio tape player This would than allow a vieo signal to be recorded.

[19Seventy7]

It was actually the 8 bit Guy's video that made me think of the idea but it used technology designed to do this. I haven't seen any done by Techmoan - he did do one with videos on 45s if that's what you're thinking of?


Thanks

[cmjones01]

There was a Fisher-Price toy camcorder which used an audio cassette to record video. I think it ran the tape fast and used a simple digital compression scheme (throwing away most of the image!) to get its crude results.

An unmodified audio cassette recorder, even the very best with frequency response up to 20kHz on a good day, won't even record the sync pulses usefully, never mind any picture content.

Chris

[Davewantsone]

As a post script, way back in 1970 I had a video recorder that used linear scan. It had 7 inch spools of tape and would go so fast that the tape would last for around 4 minutes. Even then on 405 lines the picture was poor. The sound was good though!

[Restoration73]

If you could convert the composite video to Baird 32-line standard electronically this
would fit on an audio track.

[19Seventy7]

Thanks for the replies.

I did take tape speed into account, and expected very poor quality image results, if any but was expecting them more than not.

I did try find out online freqeuncies of each factor, ie. the frequency when something will show on screen and tried to match this on Audacity - with no luck.

How could i convert it to Bairds 32 line standard? And how would i get a display from it? (Or would i need a converter from the 32 Lines to 625 for a standard CTV?)

Thanks

[Karen O]

Some people in the Narrow Bandwidth Television Association have done exactly as you describe: 625 -> 32 -> tape -> 32 -> 625. It is not easy, in particular, the large low frequency phase shifts of cassette recorders corrupts the waveforms making sync separation difficult.

It is only £5 to join the NBTVA cyber membership. You'd be made welcome and you never know - you might have some new ideas to bring to bear on the subject

[kalee20]

I was also thinking small line count, low bandwidth video. If Baird could make videodiscs in the 1920's (and there is even an off-air recording of BBC TV from the 1930's which somebody made using a home disc recorder) then it should be fairly trivial to use a cassette recorder in the 2010's.

I'd go out and buy an Aurora converter - quicker and cheaper than building a camera and display for 30-line!

[alynG1TBL]

Slow-scan tv would also work.

[Panrock]

Karen O (above) is being as modest as ever. She has achieved this feat herself some years ago at an NBTVA Convention and I recall seeing a very convincing demonstration.

Steve

[Karen O]

Let us not forget absent friends who achieved such feats long before I arrived on the scene, Steve.

[19Seventy7]

Thanks for the replies

I've had a look on the NBTV website, and will seriously consider it. I would be quite interested in getting it working. I think Audacity has a syncing system, which might help.

How much are the aurora converters? (I would also like to get into 405 Televisions too)

I've never heard of slow-scan TV before, but I've just googled it. Is it a software and phone application, or are there special TVs for this?

It'd be interesting to see Karens work, and how she did it, if possible, too.

Thank you for the replies!

[Dave Moll]

Originally Posted by kalee20

If Baird could make videodiscs in the 1920's (and there is even an off-air recording of BBC TV from the 1930's which somebody made using a home disc recorder) then it should be fairly trivial to use a cassette recorder in the 2010's.

Even though these were 30-line recordings, I don't think JLB was able to extract a viewable image from them. It was only with a fair degree of computer processing that these images were subsequently recovered in the 21st century.

[Richard_FM]

Originally Posted by cmjones01

There was a Fisher-Price toy camcorder which used an audio cassette to record video. I think it ran the tape fast and used a simple digital compression scheme (throwing away most of the image!) to get its crude results.

An unmodified audio cassette recorder, even the very best with frequency response up to 20kHz on a good day, won't even record the sync pulses usefully, never mind any picture content.

Chris

That was the PXL camera, I remember it being demonstrated on Tomorrow's World, but I don't think it was sold here.

[toshiba tony]

Years ago there was a toy, Fisher Price, and it said it recorded video on an audio cassette. I got one in for repair but it's a blur now. Not the picture but my memory. Surely we must appreciate helical scan was the only way. Although Ampex and a few others tried normal methods. In fact in the 60's Philips brought a mono tv out with two reels in the top that would record video. But video longitudally (sorry re spelling) come on!
We suffered with VHS and Beta, and for what they were, were ok. I remember a guy in the 70's, he claimed to mod a reel to reel tape deck for video. A sight nowadays. (dementia setting in)

[Karen O]

The Pixelvision 3000(?) stored 90 line monochrome images at 15 frames per second onto chrome cassettes running 9 times normal speed. It included a standard converter/time base corrector for playback to a separate 525 monitor. It became something of a cult among amateur movie makers due to its ghostly blurry images.

The longitudinal VCR was the Telcan and ran tape at 200 inches/sec. The head gap was created using mosaic from video camera tubes. It worked but wasn't practical.

[Panrock]

Originally Posted by Karen O

The Pixelvision 3000(?) stored 90 line monochrome images at 15 frames per second onto chrome cassettes running 9 times normal speed. It included a standard converter/time base corrector for playback to a separate 525 monitor. It became something of a cult among amateur movie makers due to its ghostly blurry images.

Assuming a square picture, I reckon that means a video bandwidth of 180 KHz. Even at 9x speed, that was 'pushing it'!

Steve

[Paul Stenning]

More info: https://en.wikipedia.org/wiki/PXL-2000