[HN Gopher] VHS-Decode - Software defined VHS decoder
___________________________________________________________________
VHS-Decode - Software defined VHS decoder
Author : muterad_murilax
Score : 173 points
Date : 2022-12-11 12:07 UTC (10 hours ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| crispyambulance wrote:
| I find this stuff really interesting. It reminds me of another
| project where someone developed an optical scanner to capture the
| shapes of vinyl record tracks (without making physical contact,
| of course). The idea was then to "play-back" the record by
| simulating a needle responding to the tracks in an ideal way and
| then simulate the needle's transducer and finally the turntable
| pre-amplifier.
|
| I see this project still uses an actual VHS head. I wonder if, in
| the future, folks will try to capture magnetic tape signal by
| using something like a hard drive head scanning over the top of
| the tape but not touching it? This could potentially retrieve
| signal badly damaged, unplayable tapes-- lay out a segment of
| tape on flat surface, scan it, repeat, until entire tape has been
| scanned.
| anfractuosity wrote:
| I assume this is the project you mean? -
| https://ofersp.github.io/digital_needle/ it's a shame there
| doesn't seem to be sourcecode. Very cool though.
|
| You can also get laser turntables -
| https://en.wikipedia.org/wiki/Laser_turntable which look
| intriguing
|
| I'm rather curious about these microscopes -
| https://matesy.de/en/products/magnetic-field-visualization/m...
| which can visualise magnetic fields, they're very expensive
| though.
| userbinator wrote:
| If I remember correctly, laser turntables were not popular
| because they also reproduced all the fine dust on the surface
| of the disk.
| iforgotpassword wrote:
| Yep. Every tiny dust particle makes an audible pop, while
| an actual stylus would've just pushed it out of the groove.
| interestica wrote:
| So laser turntable needs a leading 'dust plow' ?
| h2odragon wrote:
| Tangential but cool: in 1998 there were commercial, 50GB data VHS
| tapes.
|
| https://en.wikipedia.org/wiki/D-VHS
|
| about a decade after that someone asked me for help reading a
| crate of these tapes that had been flooded then stored in a shed
| for several years. Couldn't help them at all but it was an
| amusing diversion figuring out what the hell they had.
| Bluecobra wrote:
| There was also a hokey VHS tape backup card for the PC around
| the same time that used standard VHS tapes:
|
| https://youtu.be/TUS0Zv2APjU
| greggarious wrote:
| There's a store in Pittsburgh that does this for people as a
| paid service.
|
| OP's project is cool but it's my understanding the specialized
| hardware is the big barrier to doing this at home, for most
| folks, especially if you don't want the tapes routed through a
| third party for the same reason people invented the polaroid so
| you don't have to send everything to the Ritz as the mall.
| jinto36 wrote:
| There are other weird VHS-based formats, such as WVHS, which
| was used to store HD-ish analog video on VHS-
| https://en.wikipedia.org/wiki/W-VHS
|
| Alesis also developed an 8-track digital audio recorder based
| on VHS, ADAT, which used SVHS tapes and could record 20-bit
| 48khz. ADAT was pretty popular in smaller studios, and was
| great for the time before multi-gigabyte hard drives.
| https://en.wikipedia.org/wiki/ADAT
| Hackbraten wrote:
| Also, ADAT has been immortalized in the first verse of the
| lyrics in The Prodigy's _Diesel Power_ [1].
|
| [1]: https://genius.com/The-prodigy-diesel-power-lyrics
| actionfromafar wrote:
| Very cool. This could have been an excellent backup medium in a
| different timeline.
| esrauch wrote:
| Tape is a backup medium in this timeline though, just not
| exactly vhs form factor.
| nuxi wrote:
| VHS was also used for backups, see e.g.
| https://en.wikipedia.org/wiki/ArVid.
|
| And - if I remember correcly - GRAU and/or StorageTek
| robotic tape libraries also had support for VHS devices.
| matheusmoreira wrote:
| Magnetic tape is an excellent backup method even today. LTO
| cartridges already have tens of terabytes of capacity. The
| problem is there are no consumer tape drives, only expensive
| enterprise models.
| apaprocki wrote:
| Well, there used to be. The early QIC drives that hooked up
| to a FDC connector like the 3.5" were pretty ubiquitous in
| the prosumer world. They eventually transitioned to better
| tapes/standards, but all worked well and even Windows
| eventually had native support (via Microsoft Backup). I
| restored my files off of these tapes 25 years after
| recording them, so I'm grateful they existed at the right
| moment in time when drives and floppies would have
| otherwise failed me. I naively assumed in modern times LTO
| must be dirt cheap due to decades of competition, but it
| never came to be.
| userbinator wrote:
| LTO is expensive because it's enterprise-oriented, and
| despite the O in the name meaning "open", seems actually
| a proprietary standard since you can't just go to their
| site and download the specs.
| amelius wrote:
| It would be great if someone could blog about the reverse
| engineering of such a tape drive here.
| SoftTalker wrote:
| It was. I remember people doing it.
| actionfromafar wrote:
| DVHS?
| drmpeg wrote:
| Linus Tech Tips just did a video on D-VHS.
|
| https://www.youtube.com/watch?v=papQ8xQxizA
|
| When I was at LSI Logic, I developed the IEEE1394 interface for
| the second generation JVC D-VHS decks (the HM-DH40000U and HM-
| DH5U). I worked directly with engineers in Japan and I used to
| get them to bring me copies of the Japanese ham radio magazine
| "CQ ham radio" when they would come to visit us in Milpitas. I
| can't read Japanese, but it's just a wonderful magazine about
| 300 pages thick (like the old Byte magazine).
|
| https://www.w6rz.net/IMG_0103.jpg
| PaulHoule wrote:
| I think of how most of the established ham radio brands are
| Japanese like that ICOM on the cover.
| h2odragon wrote:
| Very cool! Thank you for sharing that.
|
| When I was hunting information for that client; I found a
| deck and interface card on ebay for some fairly trivial
| amount, $200 or so. I was really tempted to grab it just for
| the "neat weird gear" pile but couldn't justify it. The tapes
| they wanted read had been submerged for some days and were
| crusty. The media _might_ have been recoverable but it would
| have meant pulling it out and putting the tape into new
| cartridges.
|
| Am I correct in remembering that standard VHS tapes were
| usable in these drives?
| xattt wrote:
| Just want you to know that those particular DVHS decks were
| an object of desire for a geeky teenager wanting the latest
| and greatest!
|
| I had no practical use for them as my family didn't have an
| HDTV for a few more years, nor lived in an country where 1394
| was enabled by default on cable boxes. However, the very idea
| of having a MPEG TS captured on a commodity tape was alluring
| in being able to have a perfect copy of whatever was on TV.
| rwmj wrote:
| Really nice! In case anyone was wondering, this is for capturing
| and decoding the raw VHS RF signal from special test points on
| your VHS recorder. Some hardware hacking is required:
| https://github.com/oyvindln/vhs-decode/wiki/Hardware-Install...
|
| By the way, great Japanese docudrama about the making of VHS with
| Toshiyuki Nishida and Ken Watanabe:
| https://rarefilmm.com/2020/05/hi-wa-mata-noboru-2002/
| actionfromafar wrote:
| If you are familiar with TBC or Time Base Corrector, you can
| think of this program as an offline non linear time base
| corrector with a LOT of options. Also because it takes the VHS
| data as early after tape capture as possible, a lot of
| components in the VHS player are bypassed and implemented by
| superior software.
| pmarreck wrote:
| combine this with some ML-powered artifact correction and
| perhaps a bit of upscaling and you might invent the best VHS
| digitizer available
| jacquesm wrote:
| You definitely want to tee the process before you start
| doing any ML artifact correction to make sure that it
| actually is an improvement.
| lathiat wrote:
| I wonder if this could be used to better decode tapes with some
| degradation and artefacting.
| actionfromafar wrote:
| Absolutely. While a tape player may drop out and struggle to
| recover, this software stands a much better chance of
| deciphering.
| jacquesm wrote:
| This may be a viable path to fixing up really old recordings
| as well, those tend to have a lot of noise and pops /
| crackles in them.
| lightedman wrote:
| I wonder if this could be helpful in finally making an emulator
| of the Action Maxx console system, which used VCR tapes for
| content.
| gattilorenz wrote:
| I'm not familiar with the Action Max, but the Wikipedia page
| links to this emulator:
| https://web.archive.org/web/20110405205335/http://www.jaeger...
| boboche wrote:
| too bad the first and best capture option costs several hundred
| of dollars otherwise this would be epic. Now its just awesome ;)
| gattilorenz wrote:
| The easiest supported option seems to be this:
| https://a.aliexpress.com/_mrd5cMK
| mod50ack wrote:
| Yes, which you still need to add to a VHS player.
| aidenn0 wrote:
| This uses high speed ADCs to capture the signal. Anyone know the
| bandwidth of VHS? If it's narrow enough, using a much cheaper SDR
| could be an option.
|
| The usage of a DC blocking capacitor implies it's not baseband.
| rasz wrote:
| much cheaper than $30 25MHz 16bit/50MHz 8bit cards they are
| using?
| aidenn0 wrote:
| First item in readme was much more expensive than that
| TylerE wrote:
| ~5.5mhz split 3.4m luminance 400khz chroma / 1.7mhz stereo fm
| audio
| aidenn0 wrote:
| Yeah that's too wide for say an RTL SDR
| tomphoolery wrote:
| has anyone told Technology Connections about this??
| Sporktacular wrote:
| What is it about OSS project webpages and burying any layman's
| explanation or context.
|
| It's like they've been knee-deep in it so long, surrounded by
| fellow geeks they just assume everyone should know what they're
| talking about.
| capableweb wrote:
| They owe you nothing, so if you want to figure something out,
| searching the web is your best chance.
|
| Also, how is it not clear what the project is? First thing I
| see from the submission link:
|
| > Software defined VHS decoder
|
| > A fork of LD-Decode, the decoding software powering the
| Domesday86 Project
|
| Which links to https://github.com/happycube/ld-decode and
| https://www.domesday86.com/
|
| > Software defined LaserDisc decoder
|
| and
|
| > Domesday86 is a project that aims to recreate the experience
| of the original BBC Domesday project using modern hardware and
| software
|
| Which leads me to searching what BBC Domesday is, as I didn't
| know:
|
| > The BBC Domesday Project was a partnership between Acorn
| Computers, Philips, Logica, and the BBC to mark the 900th
| anniversary of the original Domesday Book, an 11th-century
| census of England. It has been cited as an example of digital
| obsolescence on account of the physical medium used for data
| storage.
|
| Not sure why everything has to be made for/explained as it's
| made for literally everyone. Some software is for a niche
| section of programmers/developers/$niche-group, that's
| perfectly fine. If you're curious, use a search engine like the
| rest of us.
| funstuff007 wrote:
| > They owe you nothing, so if you want to figure something
| out, searching the web is your best chance.
|
| Of course that's true, but most OSS devs would prefer broader
| usage to narrower usage.
| Sporktacular wrote:
| Commercial software owes me nothing either.
|
| So, to understand it, I should know what CVBS is and click on
| links to other projects. Which I did:
|
| Apparently LD-Decode is a Software defined LaserDisc decoder.
| Great. It also buries its basic purpose in further links.
|
| As for Domesday86 Project, its About page is about project
| members, privacy policy and general disclaimers. And it's
| just weird that you think "The BBC Domesday Project was a
| partnership between Acorn Computers, Philips, Logica, and the
| BBC to mark the 900th anniversary of the original Domesday
| Book, an 11th-century census of England. It has been cited as
| an example of digital obsolescence on account of the physical
| medium used for data storage." is a good description of
| whatever it is.
|
| I have an electronics degree and I struggled to get this
| basic info, so imagine how bewildering this would be to a
| less technical audience. It doesn't need to be this way. OSS
| can do so much for people, if only the slightest effort can
| be made to let them in and indulge their curiosity.
|
| Also, before you respond with an explanation of why jargon is
| good, consider the reason you didn't boot up your computer
| with a careful sequence of toggle switch positions, is
| because someone before you was kind enough to make the
| technology accessible, even to snarky YC commenters.
| joemi wrote:
| Things don't need to be explained from base principles or
| anything like that and as you mentioned they're not beholden
| to anyone, but explaining to a bit broader of an audience
| than one's particular niche is still generally a good idea.
| It makes it easier for people not-in-the-niche-but-somewhat-
| close to be able to understand/evaluate things. It could be a
| project that's relevant to this near-to-the-niche person, but
| without somewhat broader explanation, they'd miss it.
|
| Another good idea (that no one is obligated to do) for
| project descriptions/overviews is to give a brief mention of
| why. For instance, it would have been nice if the readme for
| this project mentioned the purpose being "To bypass all non-
| essential hardware, and process it all in software directly
| for an affordable and simple way to create a true 1:1
| archival copy of analogue tape mediums." It wasn't too hard
| for me to dig a bit into the project wiki to find that out
| and piece it together, but I'm used to doing so, specifically
| because so many readmes tend to not do it themselves.
|
| Finally, you've said "they owe you nothing" and I've also
| noted the lack of obligation, but while technically/legally
| true, there are still some expectations and unofficial
| obligations to varying degrees when releasing open source
| software. Generally, the more useful/interesting the software
| is, the more expectations and unofficial obligations there
| are. Take for instance any software that has a benevolent
| dictator for life (BDFL) scenario. That term on its own has
| expectations of benevolence built-in. There are expectations
| that they'll guide the project in good directions, that
| they'll ensure bugs get fixed, and to some degree that the
| community will have some input on things even though the BDFL
| makes the final call. More generally on most projects, there
| are expectations that bugs will get fixed, pull requests
| considered/merged when appropriate, documentation will be
| provided, and so on. It's hard (perhaps impossible) to have a
| successful open source project that does not do these kinds
| of things, so in a real-world practical sense, there _are_
| obligations in open source projects, if you want any kind of
| success for the project.
| ThinkBeat wrote:
| Can I use this to defeat Macrovision copy protection on old VHS
| movies?
| jccalhoun wrote:
| This would be super overkill. There are tons of ways to get
| around macrovision.
| jeffbee wrote:
| Yes. Macrovision works by interfering with primitive auto-gain
| circuits. This would easily defeat it.
|
| You can also ignore macrovision if you have an older deck with
| manual gain.
| EGreg wrote:
| Can we have AI remove the artifacts from VHS after it is
| digitized?
|
| Anything exists like this available ONLINE?
| rasz wrote:
| no, but we can have AI hallucinate alternative "pretty looking"
| version
| Lindalee51 wrote:
| userbinator wrote:
| In terms of physical construction, I believe early 90s VCRs were
| the best. Late enough to have most of the reliability issues
| worked out, and before cost-saving became a priority. That said,
| perhaps the last designs (late 2000s?) are also alright because
| they were simplified to reduce assembly cost, but may be more
| fragile too.
| capableweb wrote:
| Slightly off-topic, but bit related:
|
| I'm about to start a project for digitalizing a bunch of
| recordings from a 1990s Sony Handycam for a film project run by a
| friend of mine. The quality doesn't have to be perfect, but I
| want to ensure I don't risk degrading the "tapes" themselves.
| Anyone know of any hardware that is up for the task? Doesn't have
| to be professional quality, but of course I want good results.
|
| Just about to start the project so haven't had time yet to look
| into what hardware I need yet, maybe people here have good ideas,
| you usually do :)
| jacquesm wrote:
| The big problem with old tape is that it tends to stick. Try
| winding it manually for a short stretch to see if the tape is
| still loose and if it isn't then you probably should contact
| someone with more expertise to get the tape to be unstuck
| before putting it in a machine. Stuck tape also tends to break
| very easily.
| jccalhoun wrote:
| assuming the camera has rca out jacks, you can get a rca to
| hdmi adapter box for less than $20. If you computer doesn't
| have hdmi capture they also make rca to usb boxes as well (I
| don't think the cables from rca to usb without a chip in it
| will work but I might be wrong). Then OBS can record it
| actionfromafar wrote:
| If the tapes are really degraded, state of the art is to
| digitize them _once_ and do that run as good as possible.
|
| Stuck tapes sometimes are stuck because of moisture. In that
| case, the tapes are "baked" at a certain temperature to get the
| moisture out. If the tapes are in really bad condition, you get
| only one chance to capture what's on them, but the flip side is
| that one run can be of pretty high quality.
|
| Edit: if your tapes are DV or Digital-8, get a camera with
| firewire out.
|
| If your tapes are Hi8 analog, get a digital-8 camera which can
| play analog tapes with firewire out. You won't get a better
| quality without going the VHS-Decode way.
|
| If none of that is an option, get a decent composite to HDMI
| converter, than capture the HDMI from that into a PC with a
| HDMI ripper.
|
| Or one of those "HDMI to SD card" rippers floating around.
| Gordonjcp wrote:
| Sony Handycam implies possibly Video 8 or Hi8 tapes.
|
| If you can get hold of a Digital8 deck that works (and well)
| then you can hook that to your PC with a FireWire card, and do
| a direct digital capture of analogue tapes. The DSP in the D8
| deck will do an excellent job of decoding, far better than an
| analogue deck, and you'll get a really clean output without all
| the "convert down/convert up/convert back down" thing you get
| using composite jacks.
|
| You'll need to convert the raw DV files into something suitable
| for editing and distributing, but I guess - since you're on
| here - you already know about ffmpeg.
|
| Here's an example of a very old - 2000/2001 or so! - tape that
| I had lying around in a box in the shed for the past 20 years.
| I shot it with a hand-held Sony Video 8 camcorder when some
| power station chimneys were being demolished near where I
| worked. This would (of course) be the day I forgot to throw a
| tripod in the car, "Oh I don't need to pack that, I've got one
| in the workshop, I'll leave mine at home..."
|
| https://www.youtube.com/watch?v=ZPmCygZIjio
|
| It was a pretty grey and drizzly day, as I recall. I could have
| got the colours up a bit in editing but I didn't feel like it,
| and this is pretty much how it came off the quite-badly-damaged
| tape.
| haunter wrote:
| I went with a lazy way to digitalize old VHS/VHS-C tapes.
| Bought a Panasonic DMR-EX99V [0] which is a DVD/HDD/VHS/TV
| tuner combo in one. That was the last model Panasonic made and
| it also has an HDMI output. So basically I recorded all the VHS
| to the internal HDD > then just moved them to the PC through
| the DVD recorder. It has a USB port but unfortunately you can't
| access the raw recorded files on the HDD that's why the DVD >
| PC step is needed. I'm not an expert probably someone could
| hack it to gain access... Anyways it was one of the better
| purchases I've made. Works perfectly and so far no problems at
| all. And it just works hence why I said lazy at the beginning,
| simple system with good quality.
|
| 0, https://m.media-
| amazon.com/images/I/71mbsPXPhzL._AC_SL1500_....
___________________________________________________________________
(page generated 2022-12-11 23:00 UTC)