[HN Gopher] Microscopes Can See Video on a LaserDisc
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Microscopes Can See Video on a LaserDisc
Author : zdw
Score : 116 points
Date : 2026-03-07 22:03 UTC (1 days ago)
(HTM) web link (www.youtube.com)
(TXT) w3m dump (www.youtube.com)
| BobMcBob wrote:
| 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.
| smusamashah wrote:
| So CAV (constant angular velocity) is an encoding format for
| laser disks. When something is written with CAV, it is basically
| analogue data and therefore repeating patterns can be recognized
| on the disk.
| jmkd wrote:
| Not simply repeating patterns, readable text from the credits
| as shown in the video.
| accrual wrote:
| Here's where the text comes into focus, pretty cool:
|
| https://youtu.be/qZuR-772cks?t=1540
| wtallis wrote:
| 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-screen
| locations of subsequent frames would be aligned at the same
| radial position on the disc, and the credits scrolling
| vertically at constant speed.
|
| If LaserDisc had used a digital encoding (especially a
| compressed encoding), the data on disc may still have had
| discernible patterns but the text would not necessarily have
| been legible. If it had used CAV but not stored a whole number
| of frames per track, then temporal and spatial locality on
| screen would not have corresponded so well to spatial locality
| on disc. And the vertically-scrolling credits are pretty much
| the only kind of content that can produce the recognizable and
| legible images on the disc surface.
|
| I _think_ the fact that the aspect ratio of the text came out
| approximately right probably is a consequence of the scrolling
| speed of the credits being chosen to suit the vertical
| resolution of the video. If the text had appeared squished in
| the microscope, it would probably have been moving too fast on
| screen to be clearly legible.
| VorpalWay wrote:
| The live stream of this had more interesting things as well, such
| as looking at the ink on mimeographs compared to inkjet printing.
| Long and rambly as live streams tend to be, but it is there if
| anyone cares.
|
| https://m.youtube.com/watch?v=zIsCswtkozI (mimeograph around
| 3:36:00 mark)
| amelius wrote:
| But the opto mechanical parts of a laserdisc reader are way more
| interesting than a microscope.
| rustyhancock wrote:
| Here's a screen capture of the end credits visible on the disc
| the videos worth it but I do think sometimes you need to start
| with the money shot https://ibb.co/v4KK88fF
| crazydoggers wrote:
| This is from a CED not a laserdisc.
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