
Digital Audio on VHS – The Technics SV-P100 [video] - miobrien
https://www.youtube.com/watch?v=WVDCxTtn4OQ
======
ilamont
I was involved in the indie music scene in the late 1980s and 1990s and recall
similar systems to this - digital audio recorded on analog videocassettes.

IIRC, WBRS, the radio station at Brandeis University, used one such system to
record live performances at the studio in two channels of digital audio
starting in the late 1980s. I also worked with a studio in Taiwan in 1997 that
used analog video cassettes to record 16 channels of digital audio, which were
then mixed down to 2 channels and burned to a CD-ROM.

One of the limitations that we were very aware of at the time was being able
to extract the audio from the tapes at a later date. No home users had gear
that could play back the tapes, and it seemed that very few studios even had
access to these specialized pieces of machinery.

In the early 1990s, I also worked in a 24-track London recording studio, which
still used very thick analog tape for multitracking, but would output demos or
test mixes to the then-emerging DAT standard
([https://www.newworldencyclopedia.org/entry/Digital_Audio_Tap...](https://www.newworldencyclopedia.org/entry/Digital_Audio_Tape)).

~~~
Scoundreller
Ahhh, DAT, the technology so good that the recording industry got congress to
make it useless:

[http://www.brouhaha.com/~eric/bad_laws/dat_tax.html](http://www.brouhaha.com/~eric/bad_laws/dat_tax.html)

~~~
Zenst
Ah yes, then the whole blank recordable media TAX on blank tapes, I remember
that, then the whole storm over writable CD's.

[https://en.wikipedia.org/wiki/Private_copying_levy](https://en.wikipedia.org/wiki/Private_copying_levy)

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aardvark179
Digital audio storage on video predates this, and even VHS, by quite a long
way. The whole reason we have the weird sample rate of CD audio is because it
was one that could conveniently be stored and retrieved as a video signal in
either PAL or NTSC.

~~~
slashink
Not the only reason. A combination of CD targeting a useable spectrum just
above 20KHz (human hearing) which meant having more than double due to
Shannon-Nyqvist (
[https://en.m.wikipedia.org/wiki/Nyquist–Shannon_sampling_the...](https://en.m.wikipedia.org/wiki/Nyquist–Shannon_sampling_theorem)
). With the need of filter cutoff on the high end, 44000 was enough to avoid
aliasing and still have a good useable spectrum.

The second part is finding a good sample rate that you can easily clock on
VHS. That’s where the this stems from although they technically could have
gone for a different sample rate at a lower bit depth. 44100 ended up being a
good trade off between different requirements.

~~~
aardvark179
Yeah. I was going to type more about the Shannon-Nyquist limit, but was on my
phone, and I've heard several people over the years assert that the 44100
sample rate was a very early form of DRM since "anybody sensible" would have
picked 48000, and indeed did for various other formats where this restriction
didn't apply.

~~~
segfaultbuserr
> the 44100 sample rate was a very early form of DRM

Can you elaborate? How could it be a form of DRM? Did you mean that 44100 Hz
was incompatible with existing designs using 48000 Hz, or that 44100 Hz
created technical challenge for replication due to its smaller frequency
margin?

~~~
garganzol
44.1 kHz sample rate limits the audio frequency response to 22 kHz. The
popular knowledge says that the human hearing "stops" at 20 kHz, but in
reality this is not a flush cut off. It may go way beyond that: some people
are able to hear up to 27 kHz, depending on age and personal physiology.

Limiting frequency response at 22 kHz ensures that you get a high quality
material, but not the highest quality.

Record labels still have the leverage to extract some pennies in the future by
selling a higher quality record and this makes them feel comfortable.

~~~
klodolph
I don’t find this argument particularly compelling. You can hear up to 27kHz
if the sound is loud enough, under laboratory conditions. However, from a
psychoacoustic standpoint, you are unlikely to be able to hear those
frequencies under normal listening conditions, and typical program material
doesn’t make use of those frequencies anyway.

In other words, 20 kHz is good enough.

~~~
garganzol
There is a bit of difference between 48 and 44.1 tracks, and it is a bit
deeper than expected.

44.1 tracks tend to be "normalized" at the highest portion of the spectrum
trying to squeeze the juice right at the studio.

Tracks mastered for 48+ kHz are usually more relaxed in this regard, they just
let the sound flow.

Both sound exceptionally well, but tracks with higher sample rate sound a bit
more natural, a bit softer if you prefer. Higher sample rate tends to add a
pleasant edge to some kinds of music: live performances, jazz, minimal techno.

If you happen to live in a part of the world where crickets are active in the
summer then take a closer look. Their audio spectrum goes way beyond 20 kHz
and if you try to listen carefully then you may spot the point where it goes
beyond 20 kHz limit.

Not everybody is physically capable to experience this. Personally I can hear
a bit of those frequencies, so it's amusing to realize that a little bug can
be such a masterful audio source. Nature is beautiful. And this beauty is a
selling point when it comes to music.

~~~
klodolph
> 44.1 tracks tend to be "normalized" at the highest portion of the spectrum
> trying to squeeze the juice right at the studio.

Could you explain this to me? What does it mean to “normalize something at the
highest portion of the spectrum”?

Assume I have a fairly solid background in signal processing theory and
understand the fundamentals of music production / mixing / mastering.

~~~
grawprog
Not the original commenter, but my guess is, because the cutoff is 22khz,
higher frequencies are normalized down around 20-22khz, blending them with
those higher frequencies and distorting and changing them slightly.

Whereas being mastered for 27khz would allow some of those higher frequencies
to remain as is and sound closer to the natural sound you'd hear.

I may be wrong but as far as I know, this is because those higher frequencies
are still picked up and interpreted by us whether we actually hear them or
not.

Personally, i've never really noticed the difference between 44.1kHz and
48kHz, but I do notice the difference between listening to audio on headphones
with different cutoffs.

20-20000hz headphones sound noticably less good than 18-22000hz or even
24000hz. It makes even more of a difference than price point usually does. To
the point where it's the only thing i really look for when looking for
headphones for music.

~~~
klodolph
> … because the cutoff is 22khz…

That’s the Nyquist frequency. The cutoff is wherever you like, but typically
at 20kHz.

> …higher frequencies are normalized down around 20-22khz, blending them with
> those higher frequencies and distorting and changing them slightly.

Can you explain what you mean by “normalized down”? It sounds like you are
describing some kind of processing done to music, something I have _never_
heard of before, something different from aliasing.

I want to assume that you’re commenting in good faith, but are you just
rewording the original comment? I don’t think the original comment makes
sense, and rewording it isn’t going to change anything.

> I may be wrong but as far as I know, this is because those higher
> frequencies are still picked up and interpreted by us whether we actually
> hear them or not.

This is wrong, or at least wishful thinking—under ordinary listening
conditions with typical program material, you simply can’t tell the difference
between music which has those frequencies and music which doesn’t. That what
experiments are testing when they test if you can “hear” something.

> Personally, i've never really noticed the difference between 44.1kHz and
> 48kHz, but I do notice the difference between listening to audio on
> headphones with different cutoffs.

Different headphones sound different, this is a known fact. There are simply
too many differences between different headphones to draw conclusions here.

When I’m making music, I try to listen to it on several headphones before I
release it. Each set of headphones I have imparts a unique sound on the music.
Same thing applies to loudspeakers.

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drmpeg
Who remembers D-VHS? Digital video on VHS.

[https://en.wikipedia.org/wiki/D-VHS](https://en.wikipedia.org/wiki/D-VHS)

~~~
jccalhoun
Of course Techmoan has done a video on it:
[https://youtu.be/jiu0LPeLQPE](https://youtu.be/jiu0LPeLQPE)

~~~
drmpeg
Cool. Thanks for the link. I developed the code for the IEEE1394 interface on
the JVC 2nd generation decks (HM-DH40000U, HM-DH5U and HM-DT100U) when I was
at LSI Logic.

~~~
ThePowerOfFuet
Username checks out.

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ethagnawl
I only started watching this channel about six months ago, but have really
been enjoying it. (I started supporting Techmoan on Patreon shortly
thereafter.)

If you're interested in hi-fi, photography, new/classic/weird/historical
technology, I'd recommend checking out the rest of Techmoan's catalog.

~~~
jasonjayr
"Technology Connections"[1] is another great channel with similar research +
documentary on old technology, with amusing jokes thrown in.

[1]
[https://www.youtube.com/channel/UCy0tKL1T7wFoYcxCe0xjN6Q](https://www.youtube.com/channel/UCy0tKL1T7wFoYcxCe0xjN6Q)

~~~
ethagnawl
Can confirm. I don't remember which one I discovered first, but the YouTube
you-may-also-like algorithm led me to the other.

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gregmac
Seeing this brings back a vague recollection of touring a radio station -- I'm
going to guess in the early 90s -- and seeing a bank of VHS machines they used
to record everything they broadcast. I think I (or someone) asked about them,
as it was weird to see video cassettes in a radio station, and so I'm fairly
sure it was actually VHS and not DAT or something proprietary. It definitely
didn't look like machine in this video. I don't remember what the radio
station was anymore, but it's very possible it was a college station.

Was this a common thing, or am I just misremembering this? Maybe just a hack a
college station would have done to use commodity hardware/tapes and get 6
hours of recording time per tape?

~~~
roywashere
At my local radio station at the end of the 90s they used the longest length
VHS tapes to record the shows on long play to 'prove' to the musicians rights
organisation which songs were played how often. The choice of medium had not
much to do with the audio quality but mostly with the length of the tapes.

~~~
ljf
I was going to post the same - I worked at a community station briefly in the
90s and they used a standard home VHS recorder that had audio (and video)
component in on the front. A 4 hour tape and long play mode you could cover 24
hours with just 3 tapes. It was all a bit diy and remembering to change the
tape if it fell in my show was pretty stressful, at least for a 17 year old.

I also understood that it was a term of our (short) license that we had proof
of what was said in air, should anyone make a complaint etc. since all our
shows were played live.

~~~
zbuf
Yeah this was hugely common in the UK, as you could fit 8 hours of Nicam
digital stereo on a VHS tape at long play, for your license obligations. And
as a bonus the security cameras as well if you need it. All using readily
available consumer gear with built-in timer. It would wear out every year or
so. Some stations used the same VHS trick as a play out system to cover
overnights as well.

I recall one of the problems is the fire hazard of keeping 8 weeks or so of
tapes.

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dsr_
Reminds me of

[https://en.wikipedia.org/wiki/ArVid](https://en.wikipedia.org/wiki/ArVid)

(Data storage on VHS)

~~~
bluedino
Video showing how it worked from LGR:

[https://m.youtube.com/watch?v=TUS0Zv2APjU](https://m.youtube.com/watch?v=TUS0Zv2APjU)

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jeffbee
VHS is a great analog tape format, too. S-VHS HiFi audio recording rivals
reel-to-reel multitrack tape quality (i.e. close to objective CD quality).
Only problem is the tape life is terrible.

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JohnTHaller
Watched this yesterday having no idea that this existed. It predates DAT and
CD and looks like a device from the future for when it was released.

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tibbon
ADAT was pretty similar to this right, but later?

~~~
wazoox
ADAT was 8 tracks of digital audio on a S-VHS. It was actually quite different
from this because it was definitely targeted to home-studios, and it didn't
use any video encoding, it was digital from end to end (and 15 years later).

