4 ms·

In reading this I'm reminded of some efforts to produce a software decoder for Laserdiscs by using a ADC sample the exact data on the disk [1] 1: https://www.d

by codys 7y ago

In reading this I'm reminded of some efforts to produce a software decoder for Laserdiscs by using a ADC sample the exact data on the disk [1] 1: https://www.domesday86.com/?page_id=978 https://www.domesday86.com/?page_id=978 I wonder if there's some way to tweak the now seemingly common SDR adapters to provide a plain ADC (ie: without demodulation). When folks are capturing old consoles, generally the RF output is avoided because of the extra noise injected. It would be ideal to work directly with the composite video. Working with the composite video also would have implications for archiving VHS and other tape-based analog footage: right now, folks tend to use hardware devices called TBCs (time base correctors) to correct issues in the video signal from a VHS player. These are all obsolete at this point and growing increasingly expensive, so it would be nice to replace this hardware with software.

makomk 7y ago
I'm not sure this is terribly practical for console capture unless you're a signal processing hacker who really doesn't want to go out and buy a capture device - decent consumer-level capture devices use some really fancy, carefully-optimized filtering to produce high quality pictures with minimal artifacting, and it'd probably take quite a bit of development and CPU time just to match the off the shelf stuff.
- Maxious 7y ago
  A reasonably priced and good quality bodge is described in "The Best Easy Way to Capture Analog Video (it's a little weird)" https://www.youtube.com/watch?v=ZC5Zr3NC2PY https://www.youtube.com/watch?v=ZC5Zr3NC2PY
  - Mathnerd314 7y ago
    So he has a $25 RCA-to-HDMI and a $70 HDMI capture card for around $100. A fully assembled Domesday board is also somewhere $100 according to https://forum.lddb.com/viewtopic.php?p=100903&sid=a582ac9ebcad2b37d24930ac444a2311#p100903 https://forum.lddb.com/viewtopic.php?p=100903&sid=a582ac9ebc..., although I guess it could be higher without a good PCB supplier. The article's Airspy R2 SDR is $169. There's a PAL decoder in https://github.com/happycube/ld-decode/blob/3d5cdeddbaf4515b41d0dff2c43faa51d649c132/tools/ld-comb-pal/palcolour.cpp#L50 https://github.com/happycube/ld-decode/blob/3d5cdeddbaf4515b..., I'm guessing it could be adapted to the article's purposes with some work. https://twitter.com/windyoona/status/1163043586314821635 https://twitter.com/windyoona/status/1163043586314821635 says she was looking at it.
  - mrguyorama 7y ago
    Despite my love for his channel, content, and personality, I think he was hugely in the wrong here. His example setup provided no better quality than my experience with a cheap analog capture device from ebay[0], though his is more pliable for other devices. [0]: https://www.ebay.com/itm/USB-Video-Capture-Converter-Analog-to-Digital-VHS-VCR-TV-to-PC-Computer-Laptop/123514920838?hash=item1cc2101f86:g:9UQAAOSwVKhcay4d https://www.ebay.com/itm/USB-Video-Capture-Converter-Analog-...
jacobush 7y ago
The domesday project is much more important IMHO for VHS and Beta captures, than for console captures. Consoles tend to have a stable timebase. Tapes tend to, especially if copies were made tape-to-tape, be very jittery. These could be almost flawlessly fixed in the domesday software, much better than any TBC. Since the capture is at the "almost RF" stage early in the tape player, the overall quality is very good too. There is the potential to view VHS in better quality than anyone has ever seen it, even back in the day.
- bscphil 7y ago
  Is there anyone using this hardware for VHS or Beta captures? Seems the original project itself is very targeted, and I'm having difficulty searching up different uses of the project. I'd considering purchasing one to do high quality VHS transfer, but I'd want a community I could turn to with problems.
  - jacobush 7y ago
    One of the committers have submitted VHS patches, so there is a community of one so far. :-) Currently it can decode to black and white I think. I am very interested also. I bought a high end consumer JVC deck unopened in box, just for this purpose in the future. But the thing is, only the mechanical transfer needs to be good, and the heads OK, the rest of the machine need not be high end at all. It really has the potential to get better VHS rips than any pro lab today in existence can achieve.
- codys 7y ago
  I think you may be misunderstanding what I'm referring to as "RF" in my comment. In the specific case of old consoles (and VCRs and other equiptment, though this isn't really relevant), there is a built-in or external "RF modulator" which takes the video (composite in this case) & audio signals and modulates them such that they appear as a TV station on channel 3/4 (typically). This is an additional signal conversion from the unmixed and not-modulated-with-a-carrier-frequency signal that is composite + audio, and tends to have additional losses when restoring it to the RGB/YCbCr signal that we actually care about vs going from plain composite to that representation. The "almost RF" you're referring to here is a different end of things, the end dealt with by domesday, etc, which is the analog signal stored to the medium in question (whether tape, laserdisc, or something else). Using that signal is, as I think we agree, a very reasonable choice for constructing reasonable archival copies.

by codys 7y ago

makomk 7y ago

I'm not sure this is terribly practical for console capture unless you're a signal processing hacker who really doesn't want to go out and buy a capture device - decent consumer-level capture devices use some really fancy, carefully-optimized filtering to produce high quality pictures with minimal artifacting, and it'd probably take quite a bit of development and CPU time just to match the off the shelf stuff.

Maxious 7y ago
A reasonably priced and good quality bodge is described in "The Best Easy Way to Capture Analog Video (it's a little weird)" https://www.youtube.com/watch?v=ZC5Zr3NC2PY https://www.youtube.com/watch?v=ZC5Zr3NC2PY
- Mathnerd314 7y ago
  So he has a $25 RCA-to-HDMI and a $70 HDMI capture card for around $100. A fully assembled Domesday board is also somewhere $100 according to https://forum.lddb.com/viewtopic.php?p=100903&sid=a582ac9ebcad2b37d24930ac444a2311#p100903 https://forum.lddb.com/viewtopic.php?p=100903&sid=a582ac9ebc..., although I guess it could be higher without a good PCB supplier. The article's Airspy R2 SDR is $169. There's a PAL decoder in https://github.com/happycube/ld-decode/blob/3d5cdeddbaf4515b41d0dff2c43faa51d649c132/tools/ld-comb-pal/palcolour.cpp#L50 https://github.com/happycube/ld-decode/blob/3d5cdeddbaf4515b..., I'm guessing it could be adapted to the article's purposes with some work. https://twitter.com/windyoona/status/1163043586314821635 https://twitter.com/windyoona/status/1163043586314821635 says she was looking at it.
- mrguyorama 7y ago
  Despite my love for his channel, content, and personality, I think he was hugely in the wrong here. His example setup provided no better quality than my experience with a cheap analog capture device from ebay[0], though his is more pliable for other devices. [0]: https://www.ebay.com/itm/USB-Video-Capture-Converter-Analog-to-Digital-VHS-VCR-TV-to-PC-Computer-Laptop/123514920838?hash=item1cc2101f86:g:9UQAAOSwVKhcay4d https://www.ebay.com/itm/USB-Video-Capture-Converter-Analog-...

jacobush 7y ago

The domesday project is much more important IMHO for VHS and Beta captures, than for console captures. Consoles tend to have a stable timebase. Tapes tend to, especially if copies were made tape-to-tape, be very jittery. These could be almost flawlessly fixed in the domesday software, much better than any TBC. Since the capture is at the "almost RF" stage early in the tape player, the overall quality is very good too. There is the potential to view VHS in better quality than anyone has ever seen it, even back in the day.

bscphil 7y ago
Is there anyone using this hardware for VHS or Beta captures? Seems the original project itself is very targeted, and I'm having difficulty searching up different uses of the project. I'd considering purchasing one to do high quality VHS transfer, but I'd want a community I could turn to with problems.
- jacobush 7y ago
  One of the committers have submitted VHS patches, so there is a community of one so far. :-) Currently it can decode to black and white I think. I am very interested also. I bought a high end consumer JVC deck unopened in box, just for this purpose in the future. But the thing is, only the mechanical transfer needs to be good, and the heads OK, the rest of the machine need not be high end at all. It really has the potential to get better VHS rips than any pro lab today in existence can achieve.
codys 7y ago
I think you may be misunderstanding what I'm referring to as "RF" in my comment. In the specific case of old consoles (and VCRs and other equiptment, though this isn't really relevant), there is a built-in or external "RF modulator" which takes the video (composite in this case) & audio signals and modulates them such that they appear as a TV station on channel 3/4 (typically). This is an additional signal conversion from the unmixed and not-modulated-with-a-carrier-frequency signal that is composite + audio, and tends to have additional losses when restoring it to the RGB/YCbCr signal that we actually care about vs going from plain composite to that representation. The "almost RF" you're referring to here is a different end of things, the end dealt with by domesday, etc, which is the analog signal stored to the medium in question (whether tape, laserdisc, or something else). Using that signal is, as I think we agree, a very reasonable choice for constructing reasonable archival copies.