Recording video on an audio cassette single speed, possible?

[ProDigit]

Last year, the 8-bit guy introduced me to the PX2000 via his youtube channel. Video here:
https://www.youtube.com/watch?v=TCXJ5twf5tM

It's a fisher price PXL-2000 camcorder that uses audio cassettes to record video on, built in 1987.
The device itself could record about 11 minutes of video, on a 90 minute cassette (5.5 minutes per side), at a resolution of roughly 10kpix, or 120x90 pix. The device ran the audio cassette tape at 9x the speed, to have sufficient bandwidth to record the pretty much 'raw' audio and video data.

The device was a total failure, due to the required bandwidth to record video footage on, The low resolution, the high tape drive recording speed, and the extremely bad lighting (high f-ratio of the lens, and low quality CCD sensor).

But times have changed, and so do our video encoders, our CCD chips, and our mobile CPUs.


Recording video footage on a cassette is by no means a replacement for current technology, but it's interesting from a point of view that 'it can be done'.


I've done some digging in the interweb, but found a lot of conflicting data concerning the speed and data that could be retained on a tape.
So from a point of view of comparing to older technologies, I can't state much.

Modern technology has improved since the 80's, and it's possible to have much more data on a tape, than was prior possible.
Cassette tapes basically work like old dial up modems; while it's still possible to get DSL speeds out of a tape, through more optimal use of frequency bandwidth.

There's not a lot of study done on what bandwidth is achievable from a tape, but I think I can estimate (open for any correction here, I'm only guessing)
When comparing tapes to audio CDs,
Audio CDs run at 16 bit, with a 20-20kHz resolution,
Audio tapes run at ~10 bit, with a ~25-18kHz, but more likely the cheaper tapes have a frequency response of ~30-16kHz.

The data of an Audio CD, roughly is 10MB/minute of audio (roughly 700MB of space for 70 min of music).

Based on the lower bitrate and audio frequency of cassette tapes, they should get about ~350MB per 70 min (175MB/side).

Tape drives aren't as precise as CD drives. They suffer of WOW and flutter, which could potentially corrupt data, thus the above number would be lower than that.
I've read somewhere on the webs (lost source), that a regular 60 minute cassette could hold up to 275MB of data, which is very close to the 300MB I would have calculated (350MB / 70min = 300MB / 60min).

I think a lot of people here could say how much video footage could fit in 275MB, 137MB per side;
If I had to guess, I've seen 480p streaming videos, stream as low as 65MB of file size per 20min of video footage using Opus as sound codec, and H.265 as video codec.

In that case, each side could host about 40 minutes of video footage, on a 60 minute audio cassette tape.

So, it might be possible to actually record 480p video footage, with current encoders, on a regular audio cassette, at single speed!

At the minimum, a device like this needs a 410k pix camera (about 41x larger), and at best, using quarter pixel motion, this device will need a 1708x960 pixel CCD (or 1.6Mpix), for optimal recording.

I wished there were some companies (esp. looking at China now, as this probably will not be a product that will attract many), that would invest a little R&D, pair a small CCD sensor, and recreate this ancient technology.
Just to see how far we've come.
And record video footage of reasonable quality, on an audio tape!

While the sales of audio tapes are on decline,
Playing video footage from an LP has been done, through Video LP.

Now where's the audio tape version?

Just thought of spitting the idea out here!

[mariush]

Well, the first thing would be to change the read heads so that they'll work like the VCR did, see at around 6:30 https://www.youtube.com/watch?v=KfuARMCyTvg
This way you can record diagonally, and you get more data per inch of tape or whatever unit of measurement you want.
Audio can probably be squeezed in around 10 kbps (for opus 22050 mono or something like that) which would leave maybe 100 kbps available for video, maybe a bit more (as you use full width of the tape)... hevc/h264 encoded 320x240 would be fine in that bitrate.

[Cary Knoop]

Originally Posted by ProDigit

I wished there were some companies (esp. looking at China now, as this probably will not be a product that will attract many), that would invest a little R&D, pair a small CCD sensor, and recreate this ancient technology.
Just to see how far we've come.
And record video footage of reasonable quality, on an audio tape!

You got to be kidding!

[StainlessS]

How bout on vinyl ? (bring back ol' 78's)



EDIT: In the 80's, the Sinclair QL computer used the MicroDrive Cartridge:- https://www.google.com/search?q=sinc...wrHABEVH6ErvM:

A plastic cartridge about 1.2 x 1.5 x 0.25 inches,
containing about 7 meters of 1/8 inch high quality video tape in a continuous loop (there was a twist in loop),
and took about 7 seconds to scan entire loop, and gave fast access to ~110 -> 120 KB of data. (fast compared to about 10 mins
for the audio cassette used by nearly every other machine at the time).
[It usually used to take longer than 7 seconds to access all if separate files on cart, but with certain software (eg Ram Disk), it could do single sweep and get all at once in single 7 second cycle.]
Total capacity varied due to there usually being some bad sectors on the medium after format, and with regular use had about a 3 month lifespan. Max possible capacity was I think about 125KB (depended a bit upon exact length and tape stretch), I only ever had one cartridge without any bad sectors.
The QL had two such microdrive devices as standard.

EDIT: Here image, innards showing the "twist":- https://www.google.com/search?q=sinc...cmxIP1uEMrQTM:

EDIT: The Sinclair QL on Wikipedia:- https://en.wikipedia.org/wiki/Sinclair_QL
Apparently, Linus Torvalds based Linux on the Sinclair QL QDOS (which had the first pre-emptive multitasking OS for a microcomputer).
QDOS was written by Tony Tebby (I once shared a stand at a computer show with him), head engineer for Sinclair Research,
and later main man at software company Q-Jump.
EDIT: Tony Tebby on Wikipedia:-https://en.wikipedia.org/wiki/Tony_Tebby
EDIT: This is Tony as I remember him:- https://www.google.com/search?q=%22t...407RZYOgwkUzM:
Note the silk cravat in some images of Tony, gives him a bit on an avant garde kind of look, but is in fact due to some kind skin sensitivity
and cravat stops shirt collars from causing a rash on his neck.

[ProDigit]

Originally Posted by mariush

Well, the first thing would be to change the read heads so that they'll work like the VCR did, see at around 6:30 https://www.youtube.com/watch?v=KfuARMCyTvg
This way you can record diagonally, and you get more data per inch of tape or whatever unit of measurement you want.
Audio can probably be squeezed in around 10 kbps (for opus 22050 mono or something like that) which would leave maybe 100 kbps available for video, maybe a bit more (as you use full width of the tape)... hevc/h264 encoded 320x240 would be fine in that bitrate.

You think that the available bandwidth is only 110kbps?
Opus works great at 48kHz (cuts of internally at 16kHz/channel), 24kbps, stereo, when framebuffer is set to 40. That would leave 75-85kbits for the video stream.
I was under the impression h.265 could squeeze about 480p video in there, when using a quality factor, rather than basing the video on a fixed bitrate.

[wonkey_monkey]

Originally Posted by mariush

This way you can record diagonally, and you get more data per inch of tape or whatever unit of measurement you want.

You could still get the same amount of data on the same amount (area) of tape if you record horizontally, but the tape would have to be longer and thinner and run through at a higher speed.

[Phanton_13]

Streamer cassettes a digital storage medium that used cassettes had up to 160 MB, but I don't know tape duration or lench. On a normal cassette is posible to store between 120 to 240MB in a 90' tape with advanced DIY technology.

This links are interesting, specially in the coments/posts:
https://hackaday.com/2016/10/22/maki...age-interface/
https://hydrogenaud.io/index.php/top...msg939914.html

[Ghitulescu]

[pandy]

Since 70's there is huge progress on coding and storing information thus i can imagine relatively well working solution for storing video on audio cassette but i see no sense in this.
Typical bandwidth of audio cassette is around 100Hz - 12.5kHz, SNR practically reachable is around 40Db thus also ok, serious issue are related to dropouts but in general with proper coding you should be able to get around 250 - 300kbps in reliable fashion. Such bitrate is sufficient with modern codecs to deliver some VCD quality.
But why? Audio cassettes are expensive when compared to other storage formats, also their quality is way bellow average quality in 80's.

[Ghitulescu]

Everyone rans away from tape, since tape is linear (people that think of cassettes and open reels NEVER had a chance to work with them - they don't have any idea how is to change the reels in midway, how to find a particular position/song on a cassette or tape, and other "beneficial" advantages a linear medium has).
Those people jumped in the CD party so fast that in 4 years no LP and no R2R device has been manufactured after (the cassette only survived till the break of DAT and CDR recorders).

Besides, the storage density of regular magnetic tapes are abysmal low compared to anything like. Any error on a tape (and it's so easy to have a tape mechanically destroyed, even in its reproduction apparatus) would practically render the whole information (or at least the information from that poin onwards) completely useless. DAT and MiniDV devices refuse to pass over such an error, this also renders the splicing (= joining two tapes together) useless.

Tapes are a good medium only for those that care about them, like big data corporations and stuff, and they carry out a 5x redundancy system. I wonder what normal user would pay 5 times the 3digit price of each of the 5 cartridges, when a HDD (even SSD) of the same storage space is below 2 digits?

Cassettes, tapes and LPs in audio are only hypes meant to squeeze another $ from the unsuspecting but believing user. If you earn your money hard, spend it equally as hard...

PS: a cassette is only able to provide 50-20k at -20dB below reference, at normal recording level (0dB) only the best recorders can get 9k out of them, usually is 7 or even lower.
Theory is nice but the praxis is killing us