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Posted by zdw 1 day ago

Microscopes can see video on a laserdisc(www.youtube.com)
438 points | 55 commentspage 2
Aardwolf 2 hours ago|
Now I wonder if something similar is possible with the magnetic fields on VHS tape
valleyer 1 hour ago|
Thoughts on that: (1) you'd need a way to visualize the magnetic fields, (2) the data is frequency modulated, (3) due to helical scan, the video field lines do not line up evenly one over the next as they did so nicely in the Laserdisc / CED (there'd be a skew).

So I don't want to say it's impossible, but I think it would require a lot more creativity.

throwaway85825 4 hours ago||
The title should have an asterisk.
oofbey 11 hours ago||
Fun fact about laser discs. They are analogue not digital. CD’s store digital information with the presence or absence of pits. Fairly ancient but still fundamentally feels like a very old version of a thumb drive.

Laser discs are not digital. They encode the analogue video signal’s value as the length of the pit. It is digitized in the time domain - sampled at some frequency, but the “vertical” signal value is stored entirely analogue. In terms of encoding it’s more similar to a VHS tape than a CD. Kinda crazy.

bregma 1 hour ago||
> Laser discs are not digital... It is digitized in the time domain

Laser disks are 100% digital (as you said, they store digits in the time domain).

They don't encode their data using binary like a CD does.

"Binary" and "digital" are two separate and unrelated concepts.

actionfromafar 21 minutes ago||
Um... I think they store "PCM encoded-ish" but the length of the pits are not discrete on / off like on a CD but various arbitrary lengths, so analog.

The sound was also analog to begin with, then the same encoding as CDs, then after that AC-3 and DTS.

a-dub 10 hours ago|||
yeah i remember learning this as a kid and being surprised. i originally thought laserdiscs were modern high tech, but then they turned out to actually be from the late 70s/early 80s with the primitive analog video encoding where red book audio cds of the mid to late 80s were actually digital.
VerifiedReports 8 hours ago|||
BUT... Pioneer put AC-3 (Dolby Digital) surround on LaserDiscs before DVDs came out. So LaserDiscs were the first video medium to offer digital sound at home.

And at that point, most players sold were combo players that could also play CDs.

And there was one more disc format: CD Video. It was a CD-sized digital single that also had a LaserDisc section for the (analog) music video. I have a couple; one is Bon Jovi.

throwaway85825 4 hours ago||
Was CD video compressed? I thought it existed at the same time as DVD but cheaper.
yourusername 3 hours ago||
That's Video CD. It existed before DVD but survived alongside it (mainly in Asia) as a cheaper alternative.
mh- 10 hours ago|||
I just learned this in my 40s and am surprised. Very cool.
qsera 5 hours ago|||
So how does writes work? Does an analog signal translate into pit-lengths with absolute precision?
throwaway290 5 hours ago||
Everything is analog when it gets to real world
amelius 13 hours ago||
But the opto mechanical parts of a laserdisc reader are way more interesting than a microscope.
SV_BubbleTime 9 hours ago||
Very cool but, I was hoping he was going to spin it and align with the camera’s refresh rate.
system2 5 hours ago|
That would be cool with a variable motor and a 3d printed mount maybe.
JohnnyLarue 10 hours ago||
[dead]
macshome 8 hours ago|
That’s not a LaserDisc, it’s a CED video disk. Totally different technology.
ZeWaka 8 hours ago||
A LaserDisc was featured in the video alongside the CED video disk.