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Re: Why wasn't there ever a VHS based consumer audio format?

Reply #25

Oh, they're actually using the entire picture frames to encode the data! That's pretty neat! makes me want to convert this into an arbitrary tape data storage...

Whatever for?

For fun and nostalgia? ;-)
I wonder whether that person with the "fuck you i'll keep downloading 32/192 rips" comment below the Youtube vid is audiophile or just sarcastic.

The data rate is a paltry 1.4 megabits/second.

But that is because it is constrained to be played back on with a conventional machine in realtime, right? So it is limited by SLP playing speed AND the PCM format?

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #26
There was a system to use VHS as computer a data backup device. I remember refusing to take it seriously: compared to the metal-backed cartridges, it seemed cheap (which, comparatively, it was), fragile, domestic and somehow amateur! Which reveals that I was probably just being a snob. Years later I was happily feeding machines with the DAT cartridges.
The most important audio cables are the ones in the brain


Re: Why wasn't there ever a VHS based consumer audio format?

Reply #28
There was a system to use VHS as computer a data backup device. I remember refusing to take it seriously: compared to the metal-backed cartridges, it seemed cheap (which, comparatively, it was), fragile, domestic and somehow amateur! Which reveals that I was probably just being a snob. Years later I was happily feeding machines with the DAT cartridges.

Not sure if you and @Porcus are talking about the same thing, but using VHS as a tape drive for computer data was somewhat popular in Russia, iirc. I've only seen it quite recently, at maker fares and other conventions. It worked with regular VHS VCRs, and it was basically something that attached to the parallel port on one side, and the Composite connector on the other. Similar to the Commodore Datasette, except it could be used with any VCR.

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #29
Whatever for? The data rate is a paltry 1.4 megabits/second. That's 635 megabytes per hour, AKA 0.635 gigabtye per hour. To add a little insult the error correction isn't great and consumer tape deck reliability was.....

 I bought a 2 terabyte drive last week at Fry's for $59. That is 2000 gigabytes that can transfer at 80 megabytes/second and fits in a shirt pocket. It also plugs into any computer with a USB port.

YOUR project however would be pretty secure as nobody could play and decode your tapes.


As an electronics engineer and embedded developer, I like making things like that. Not for the practical purpose but just making quirky things like that is fun and sometimes has some artistic value to it.

A couple years ago I converted a D-VHS recorder to to a block device, by controlling the shuttle mechanism and packing arbitrary data into blocks that were copied into a static buffer, bypassing the MPEG2 video decoding section. The problem was, that I had to give the D-VHS VCR back to the owner. Apparently, they're as rare as dinosaur teeth and highly valuable and collectible.

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #30
There was a system to use VHS as computer a data backup device. I remember refusing to take it seriously: compared to the metal-backed cartridges, it seemed cheap (which, comparatively, it was), fragile, domestic and somehow amateur! Which reveals that I was probably just being a snob. Years later I was happily feeding machines with the DAT cartridges.

Not sure if you and @Porcus are talking about the same thing, but using VHS as a tape drive for computer data was somewhat popular in Russia, iirc. I've only seen it quite recently, at maker fares and other conventions. It worked with regular VHS VCRs, and it was basically something that attached to the parallel port on one side, and the Composite connector on the other. Similar to the Commodore Datasette, except it could be used with any VCR.

I have used something like that with amiga 4000, it could store about 1 megabyte per minute (irc).
PANIC: CPU 1: Cache Error (unrecoverable - dcache data) Eframe = 0x90000000208cf3b8
NOTICE - cpu 0 didn't dump TLB, may be hung

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #31
Makes me wonder if any of those existing technologies behind modulating digital audio to magnetic media (like ADAT) could be modified to work a normal cassette tape that carries digital audio (lossy or lossless doesn't matter) instead of analog audio. It would prove a great middle ground for the niche market of people who recently returned to older media storage solutions for whatever reason. It could breathe a bit of new life to the anciented format. Is there a way to fit enough digital data reliably on the effective bandwidth of a regular old cassette tape? All solutions that I know of are either unreliable or their data rate is way too low for audio. There must be a way though with today's knowledge and technology.

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #32
Back in the '70s I used a 600 baud modem to record onto cassette tape and read it back. Not very fast, but it worked.

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #33
Back in the '70s I used a 600 baud modem to record onto cassette tape and read it back. Not very fast, but it worked.
600 baud is not enough data rate for audio. But we have come a long way since the 70s and old FSK modulation. I can think of a theoretical way that I could store nearly to 100kbps on a tape using two band folded modulated signals of two 56kbps modems on the most flat response parts of a tape but there MUST be a more educated and more efficient way to do it out there. The answer may be already on one of the methods used on VHS tapes that carried digital audio on a way or an other. There are videos on YouTube that show PCM digital audio being modulated in the video track of the tape and can be seen when played back with a regular VHS Player. There must be a way that this could be replicated to a cassette tape in a reliable way with a total capacity that could store an album of audio in a pretty good audio quality if not losslessly. Think of it like how D-VHS used regular SVHS tapes. The medium was the same but there is a lot of sophisticated modulation going on behind to end up delivering a total size of 25GB+ on a regular SVHS tape. Can't we somehow use these for Compact Cassette without changing anything as a hardware aspect?

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #34
100kbps?  Really?  Last time I checked, we've hit 2018.


Re: Why wasn't there ever a VHS based consumer audio format?

Reply #35
Makes me wonder if any of those existing technologies behind modulating digital audio to magnetic media (like ADAT) could be modified to work a normal cassette tape that carries digital audio (lossy or lossless doesn't matter) instead of analog audio. It would prove a great middle ground for the niche market of people who recently returned to older media storage solutions for whatever reason. It could breathe a bit of new life to the anciented format. Is there a way to fit enough digital data reliably on the effective bandwidth of a regular old cassette tape? All solutions that I know of are either unreliable or their data rate is way too low for audio. There must be a way though with today's knowledge and technology.

DCC used physically the same tape as the compact cassette, right?

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #36

600 baud is not enough data rate for audio. But we have come a long way since the 70s and old FSK modulation. I can think of a theoretical way that I could store nearly to 100kbps on a tape using two band folded modulated signals of two 56kbps modems on the most flat response parts of a tape but there MUST be a more educated and more efficient way to do it out there. The answer may be already on one of the methods used on VHS tapes that carried digital audio on a way or an other. There are videos on YouTube that show PCM digital audio being modulated in the video track of the tape and can be seen when played back with a regular VHS Player. There must be a way that this could be replicated to a cassette tape in a reliable way with a total capacity that could store an album of audio in a pretty good audio quality if not losslessly. Think of it like how D-VHS used regular SVHS tapes. The medium was the same but there is a lot of sophisticated modulation going on behind to end up delivering a total size of 25GB+ on a regular SVHS tape. Can't we somehow use these for Compact Cassette without changing anything as a hardware aspect?
The video bandwidth of a consumer VCR is somewhere around 3mHz.  The absolute maximum practical bandwidth of any consumer audio tape is around 20kHz.  You could figure this out even using the "new math" of the 1960s.  Unless we re-define "pretty good".   Why do you think tape, both analog and digital, have been abandoned?  


Re: Why wasn't there ever a VHS based consumer audio format?

Reply #38

600 baud is not enough data rate for audio. But we have come a long way since the 70s and old FSK modulation. I can think of a theoretical way that I could store nearly to 100kbps on a tape using two band folded modulated signals of two 56kbps modems on the most flat response parts of a tape but there MUST be a more educated and more efficient way to do it out there. The answer may be already on one of the methods used on VHS tapes that carried digital audio on a way or an other. There are videos on YouTube that show PCM digital audio being modulated in the video track of the tape and can be seen when played back with a regular VHS Player. There must be a way that this could be replicated to a cassette tape in a reliable way with a total capacity that could store an album of audio in a pretty good audio quality if not losslessly. Think of it like how D-VHS used regular SVHS tapes. The medium was the same but there is a lot of sophisticated modulation going on behind to end up delivering a total size of 25GB+ on a regular SVHS tape. Can't we somehow use these for Compact Cassette without changing anything as a hardware aspect?
The video bandwidth of a consumer VCR is somewhere around 3mHz.  The absolute maximum practical bandwidth of any consumer audio tape is around 20kHz.  You could figure this out even using the "new math" of the 1960s.  Unless we re-define "pretty good".   Why do you think tape, both analog and digital, have been abandoned?  

Because none of the methods used in the VHS methods use even near to something that would need such bandwidth. All of the practical uses use a extremely tiny fracture of the available bandwidth and the rest is left unused. Also even then, the modulation methods used are pretty non sofisticated and don't target bandwith efficiency, they don't even try. With bandwidth efficiency in mind we could theoretically do something notable on regular compact tapes.

BTW, VHS has about 1MHz bandwith for luminance, so since everything is being modulated on the luminance carrier we will talk only about that.

Also one thing that I forgot to mention is that with the 1MHz bandwith of VHS you get around 28.5Mbps data rate. With the same math, I think that even with 20kHz bandwith we could achieve something that creates audio that wouldn't upset anyone (something around 192kbps).

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #39


Because none of the methods used in the VHS methods use even near to something that would need such bandwidth. All of the practical uses use a extremely tiny fracture of the available bandwidth and the rest is left unused. Also even then, the modulation methods used are pretty non sofisticated and don't target bandwith efficiency, they don't even try. With bandwidth efficiency in mind we could theoretically do something notable on regular compact tapes.
Hmmm... Well, the 14 bit EIAJ method used roughly a half of the available bandwidth (44.056x2x14=1233568) with just the raw PCM data, plus 34% error correction in a CRCC block, plus P/Q bits, plus you do actually need about double the actual bandwidth to get reliably recoverable 0-1 data transitions, so I guess it depends on how you define "extremely tiny fraction".  Sony "stole" the Q word for two more bits of audio, at reduced error correction to 24% (believe me, it wasn't always enough!). Sure, it's inefficient.  It was 1982!  But it fit in 3mHz of consumer video tape, and pretty much worked.  Anything you do to a raw 1.5mbps bit stream to get it into 20kHz will be audibly lossy, and that's not considering the error correction you''d need for analog 1/8" wide 1 7/8 ips tape.  You must have no idea of what kind of dropouts occur on that stuff.  I don't see why you'd bother, or why anyone would want to...ever. 

 Hence, my Jurassic Park thing.

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #40
Also one thing that I forgot to mention is that with the 3MHz bandwith of VHS you get around 28.5Mbps data rate. With the same math, I think that even with 20kHz bandwith we could achieve something that creates audio that wouldn't upset anyone (something around 192kbps).
Gotta be something wrong with that math....

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #41

DCC used physically the same tape as the compact cassette, right?
Um.....no....
https://en.wikipedia.org/wiki/Digital_Compact_Cassette

Um ... well?

The tape speed of DCC is the same as for analog compact cassettes: 1 7⁄8 inches (4.8 cm) per second, DCCs use tape that is the same width as that from analog compact cassettes: 1/8 of an inch (3.175 mm). The tape that is used in production cassettes is chromium dioxide- or cobalt-doped ferric-oxide, 3-4 µm thick in a total tape thickness of 12 µm,[6] identical to the tape that was widely in use for video tapes.

Isn't that the same as a CrO2 cassette tape? Same material and same width (and, about the same thickness)?

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #42

Um ... well?

The tape speed of DCC is the same as for analog compact cassettes: 1 7⁄8 inches (4.8 cm) per second, DCCs use tape that is the same width as that from analog compact cassettes: 1/8 of an inch (3.175 mm). The tape that is used in production cassettes is chromium dioxide- or cobalt-doped ferric-oxide, 3-4 µm thick in a total tape thickness of 12 µm,[6] identical to the tape that was widely in use for video tapes.

Isn't that the same as a CrO2 cassette tape? Same material and same width (and, about the same thickness)?

Audio and video tape formulations are different, even if they might share dimensions, speeds, etc.  There are trade-offs to be made between drop-outs, output, coercivity, linearity, etc.  DCC and the video portion of a VCR used more or less saturation-mode recording, whereas audio tape tries to avoid saturation of the audio portion of the signal.  Tapes were optimized for each use. 

Pardon my frustration, but why are we talking about this anyway?  DCC failed decades ago, and nobody in their right mind is recording PCM on video tape today, much less trying to put PCM on an audio cassette. 

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #43

Also one thing that I forgot to mention is that with the 1MHz bandwith of VHS you get around 28.5Mbps data rate. With the same math, I think that even with 20kHz bandwith we could achieve something that creates audio that wouldn't upset anyone (something around 192kbps).
And what's wrong is....

Frequency bandwidth and bit rate are not directly convertible.  Frequency bandwidth is generally defined as the area of spectrum between two -3dB down points.  While data can be carried on a frequency modulated carrier, the actual occupied bandwidth of the modulated signal is quite variable and impacted by things like modulation method, noise, etc.  There's no simple conversion between the two.  And so what if you could get 100kbps on and off a cassette?  Why?  Aren't we doing uncompressed FLAC/ALAC and at least 256k compressed?  What do you do about dropouts?  Speed instability (you want jitter?  I'll show you jitter!!!). 

You know, we can also communicate using two titanium cups and a single strand of Nichrome wire.... but why would we?

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #44
Pardon my frustration, but why are we talking about this anyway?  DCC failed decades ago, and nobody in their right mind is recording PCM on video tape today, much less trying to put PCM on an audio cassette. 
Because somebody started a "Makes me wonder". I don't miss cassettes - compact cassettes, DCCs nor VHS - but should that stop me from wondering what would be possible?

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #45
Well, a tape system that intersects video cassettes and storing arbitrary data very well, is Data8/Mammoth.
It used regular, but re-branded Digital8 camcorder video cassettes, which in turn are basically regular Hi8 tapes but with higher grade magnetic grain layer. The Hi8 tapes in turn are regular Video8 tapes, but with higher quality magnetic layer, themselves.

All tapes use the same mechanical structure, and the same transport and drive mechanism. Technically, you could use a regular Video8 tape for a Data8 system, but the error rate would be much higher.

And technically, a D-VHS tape is very similar to an S-VHS tape, which in turn is very similar to a regular-grade VHS tape. The only difference, is the tape itself. It would be quite interesting to find out the difference in formulation between D-VHS and S-VHS. I tried googling a bit, but it mainly turned out inconclusive. So technically, I think saying D-VHS is a VHS based digital storage system by design, although I've never seen it extrapolated as a data storage system for arbitrary data (apart from my own project which I've talked about in a previous post).

The highest grade of tape I've ever seen, is 9-track tape from the mid-80's. The tape was matte, and felt quite thick. It was almost totally black in color. In the days of 9-track tape - which was a very popular computer data tape format - different grades of tape were available. It depended on the tape drive and error correction constraints, as well as data density. Supposedly, the higher graded tapes would last longer, but when I've worked with them in 2006, they all were in great shape, no matter if they were of lesser or higher grade. 9-track tape is a linear format, though. Tape speeds could be quite high, the HP tape drive I've used for them was super fast, with an incredible noise. The acceleration and breaking, and reversing was in a blink of an eye.

A quick google for the tape formulations didn't turn up much, although in the case of 9-track tape, I believe the formulation was kinda kept secret.

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #46
Because somebody started a "Makes me wonder". I don't miss cassettes - compact cassettes, DCCs nor VHS - but should that stop me from wondering what would be possible?
I don't mind the wondering, but when it moves from the sublime to the ridiculous, all it does is burn time.  "Possible", in reality, should include a dose of "practical", or it's just so much Blue Smoke.

How about a "practical" digital recording system that could make a relatively lossless record of a performance and the storage medium is a roll of paper?  Oh yeah, been done.  Fidelity was pretty darn good, the error rate was low, the media lasted for a century or more, but the playback device was cumbersome and expensive, the recording device even worse, and the reproducing system was essentially an instrument similar to the one that made the recording.  The practicality-o-meter isn't exactly being pegged. And that's why we don't do that today.  Could we? Yup.  And could we, on the same storage medium - a 7-foot roll of paper just under 12" wide - store high bit-rate uncompressed stereo PCM, using lasers for recording and reading data organized into a zillion parallel tracks running over 20 inches per second.  But why on earth would we? 

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #47
Actually the capacity of an old casette is better than some imagine as is capable of a raw datarate per track ( channel ) of 115kbps assuming a bandwith of 10khz with a SNR of 35db and this mean for a stereo head a raw rate using both chanels of 230kbps enough to put Opus at 160kbps+70kbps of data correction, actually if we interface directly with the head and use a advanced motor control this can be pussed to a raw rate of between 172 to 230 kbps. Also the old streamer casettes, a derived format for data storage, had capacities of up tp 160MB.

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #48
Actually the capacity of an old casette is better than some imagine as is capable of a raw datarate per track ( channel ) of 115kbps assuming a bandwith of 10khz with a SNR of 35db and this mean for a stereo head a raw rate using both chanels of 230kbps enough to put Opus at 160kbps+70kbps of data correction, actually if we interface directly with the head and use a advanced motor control this can be pussed to a raw rate of between 172 to 230 kbps. Also the old streamer casettes, a derived format for data storage, had capacities of up tp 160MB.
Similar to my thought. Now it could have been even better if you had a head like one of those multitrack cassette recorders for amateurs that recorded on all 4 channels of the cassette on the same direction, you could have double the rate of stereo. But even that wouldn't be that important. I will try with a generic modem to transmit a 50kbps audio file and record it on a tape and then I will try to reverse the mechanism to see if the data are stored well enough to be decoded properly. If that succeeds then I bet I'm into something.

 

Re: Why wasn't there ever a VHS based consumer audio format?

Reply #49
<snip>

Because none of the methods used in the VHS methods use even near to something that would need such bandwidth. All of the practical uses use a extremely tiny fracture of the available bandwidth and the rest is left unused. Also even then, the modulation methods used are pretty non sofisticated and don't target bandwith efficiency, they don't even try. With bandwidth efficiency in mind we could theoretically do something notable on regular compact tapes.

BTW, VHS has about 1MHz bandwith for luminance, so since everything is being modulated on the luminance carrier we will talk only about that.

Also one thing that I forgot to mention is that with the 1MHz bandwith of VHS you get around 28.5Mbps data rate. With the same math, I think that even with 20kHz bandwith we could achieve something that creates audio that wouldn't upset anyone (something around 192kbps).

Talking about bandwidth on VHS and Betamax is in a seriously gray area because of the way the response is defined. Broadcast composite (2" quadruplex and 1" SMPTE C) machines are flat to beyond 4 MHz. Video CAMERAS were defined in 'lines of resolution' which has a direct correlation to bandwidth BUT the response is not flat. Looking at a sweep signal on a camera the scope response might resemble a Christmas tree on its side or a funnel shape. The specified number is when the signal falls to 5 IRE units, AKA -26dB. Remember people get sucked into numbers games and the funnel mode will keep the noise reduced but the stated resolution high. The number was WAY outside of what could even get through an NTSC system but by golly, brand X is much better than brand Y even if it looked bad.

The reason for the primer is that consumer video tapes are measured the way cameras were measured. From a practical standpoint VHS and Beta get in the 2.5 MHz range at -4 to -6 dB. BTW Beta measured and looked better (I'm a broadcast engineer for 40 years). Sony in their (lack of) wisdom made the cassette too small. Numbers game again. More time, maybe not quite as good but MORE TIME is better.

The early digital processors used what was available at the time. Could they have packed more bits? Probably but the CD was just about to be released and IT ran 44100 16 bits. Life was tough enough without inventing ANOTHER wheel.

If you want to be impressed with bang for the buck get a digital audio recorder like the Tascam DR-05. Less than $100, records on an SDHC card for many hours, multiple sample rates and bit depths, MP3 or .WAV. Much more performance than the PCM on tape and for 1.5% (corrected for inflation) of the cost.

BTW anyone experimenting with data on tape will find out a LOT about dropouts and error correction. As a comparison, over the air digital TV has a raw data rate over 33 megabits but after handling all the error detection and correction you're down to 19.34 megabits, all stuffed into a 6 MHz channel.


 
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