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Microscopes can see video on a laserdisc

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Re: Microscopes can see video on a laserdisc

#91

Post by NoMoreNicksLeft »

harrall wrote: post #88
geon wrote: post #68

As I understand it, this only works with still images that scroll vertically. Each revolution is one frame, so if you compare the data paths next to each other, they don't make up an image but the same single line of several consecutive frames. Scrolling a still image makes the same line on the screen cover a different part of the image each frame, so you can sort of make out what the original image looked like. The…

If I’m not mistaken, it also doesn’t work with LaserDiscs… it works only with CEDs. The title is a bit misleading. LaserDiscs are digital but CEDs are analog. Very different technologies.

I was under the impression that laserdisc encoded the video signal in analog. Some (all?) audio tracks were digital/pcm, however.

Re: Microscopes can see video on a laserdisc

#92

Post by itisit »

harrall wrote: post #88
geon wrote: post #68

As I understand it, this only works with still images that scroll vertically. Each revolution is one frame, so if you compare the data paths next to each other, they don't make up an image but the same single line of several consecutive frames. Scrolling a still image makes the same line on the screen cover a different part of the image each frame, so you can sort of make out what the original image looked like. The…

If I’m not mistaken, it also doesn’t work with LaserDiscs… it works only with CEDs. The title is a bit misleading. LaserDiscs are digital but CEDs are analog. Very different technologies.

LaserDiscs are not quite a digital medium. The video is an FM analog signal (composite). Digital PCM audio was introduced about half a decade into the format's life.

Re: Microscopes can see video on a laserdisc

#93

Post by wtallis »

xattt wrote: post #14
wtallis wrote: post #11

Earlier quoted context omitted.

No, CAV has nothing to do with encoding, and both analog and digital formats have used both CAV and CLV and hybrids of the two. The legible text seen in the microscope images happens because of the combination of LaserDisc recording a raw and uncompressed encoding of the analog video signal, the way that LaserDisc used CAV to store an integer number of frames per track so that the image data for corresponding on-scre…

Is the image seen via microscope basically a readout of the image on a spectroscope? Those can have near-legible images, but most of the time they are not.

For the images seen through the microscope, the horizontal axis is the same as the horizontal axis of the video. The vertical axis of what the microscope sees is the time axis of the video: it's essentially a slit camera view of a particular individual scan line position within the frame.

Re: Microscopes can see video on a laserdisc

#94

Post by lysace »

BobMcBob wrote: post #2

Tech Tangents is one of the best retro channels on youtube but by retro I dont mean glorified nostalgia either. Shelby puts a lot of work into his videos and likes to showcase what awesome engineering went into some of the early tech that was practically magic. Love the channel and glad to see it on HN.

The real fun is on his Twitch channel. https://www.twitch.tv/techtangents

Re: Microscopes can see video on a laserdisc

#95

Post by withinboredom »

1000 years from now, someone will discover these discs and wonder why we wrote text so small and so many times across the disk. They’ll say the rainbow is for artistic effect and the repetition for religious reasons.

Some people will argue that it is for primitive digital technology and be called crazy people. Nobody will be allowed to study it except for those who go to the right schools or have the right connections.

Re: Microscopes can see video on a laserdisc

#96

Post by anfractuosity »

grishka wrote: post #86
Aardwolf wrote: post #55

Now I wonder if something similar is possible with the magnetic fields on VHS tape

I thought about that recently while researching how VCRs work before attempting to fix one. I didn't even think about seeing the actual video signal, I was just curious what the diagonal lines and control pulses on the tape look like. There are many other things as well that would be interesting to look at (all kinds of tapes, all kinds of floppies, hard drive platters, magstripe cards), but unfortunately I don't thi…

I have a magneto optic sensor that can visualise the field lines of a magstripe when using a polarising microscope - https://www.youtube.com/watch?v=c8nM4Z-hkTw

I'm going to try a VHS under it, to see what I get.

Re: Microscopes can see video on a laserdisc

#97

Post by Aardwolf »

anfractuosity wrote: post #96
grishka wrote: post #86

Earlier quoted context omitted.

I thought about that recently while researching how VCRs work before attempting to fix one. I didn't even think about seeing the actual video signal, I was just curious what the diagonal lines and control pulses on the tape look like. There are many other things as well that would be interesting to look at (all kinds of tapes, all kinds of floppies, hard drive platters, magstripe cards), but unfortunately I don't thi…

I have a magneto optic sensor that can visualise the field lines of a magstripe when using a polarising microscope - https://www.youtube.com/watch?v=c8nM4Z-hkTw I'm going to try a VHS under it, to see what I get.

Please do share if this succeeded :)

Re: Microscopes can see video on a laserdisc

#98

Post by VerifiedReports »

throwaway85825 wrote: post #49
VerifiedReports wrote: post #25

Earlier quoted context omitted.

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.

Was CD video compressed? I thought it existed at the same time as DVD but cheaper.

No; it was analog LaserDisc video. I think "Video CD" was a flavor of CD-I, which was very popular in China and was used way, way beyond the introduction of DVD. Well into the 2000s, I think.

Re: Microscopes can see video on a laserdisc

#99

Post by bregma »

actionfromafar wrote: post #66
bregma wrote: post #63

Earlier quoted context omitted.

> 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.

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.

"Digital" means you represent information using digits. Discrete numbers. "on/off" is binary. "Analog" means not using digits but instead an alternative (analogous) representation of the original data, usually continuous.

The grooves in a vinyl LP directly represent (are analogous to) the variations in sound pressure interpreted by our ears as sound. The grooves are continuously varying in direct proportion to the continuously varying sound waves. That's analog.

Converting analog video signals into a sequence of integral digits (even if it's pulsed-code modulation) is an analog-to-digital conversion, and storing those digits on a medium makes that a digital medium. It may just not be a binary digital medium.

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