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  1. Originally Posted by oln View Post
    Personally I bought it from one of the Domesday86 guys but I think he's out of boards now.

    There are some people working on making some batches for sale I think, I would suggest asking on the domesday86 project facebook page or in the #domesday86 IRC channel on freenode.
    What's the best time of day to reach them on the IRC channel to inquire about an order? I tried asking a few questions at different times but only one person responded. There are 26 people online. I know the UK is 5 hours ahead of me but I tried in the morning and afternoon as well. I don't use Facebook.
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  2. I decided to go with a CX23880 based capture card and cxadc instead. Can't beat 10 bucks! I've since seen some example decodes using this which looks as good as VHS is going to look. Heck, even LaserDisc captures look incredibly good at 28.6MSPS!

    If you want to capture RF from your VCR I would look for the service manual. I have a cheap Philips VCR and while I didn't find a service manual for the exact model, I did find one for the VR550 on manualslib.com. My machine, although it probably costed $80 new, tracks surprisingly well. In this case the test point is one of the many jumpers on the main board. I located the RF and ground test points after referencing the service manual's RF calibration section.

    Last edited by Titan_91; 3rd Nov 2019 at 19:08.
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    Hello,
    But what is about signal level? As far as I know cx2388x accept relatively high level of signals near 0.775 v video signal can be also 1.5 V. Video out from RF control is low may be 100+ milivolts. What is the solution ? Can head RF control point to be directly connected with video input of the board (input of the cx2388x?)?
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  4. According to oyvindln nothing needs to be done with regards to signal level. Itís ideal for the Conexant chip input via the luma pin on the s-video port.

    https://github.com/happycube/ld-decode/issues/16
    Last edited by Titan_91; 7th Nov 2019 at 11:56.
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  5. Well you want to use it with a deck where you can tap the signal after the RF amplifier. Couldn't get strong enough signal on my JVC deck for the cx88 card (but the same worked with the DdD). My Sony deck gives a much stronger signal, so I presume the rf test point on that one may be after the rf amp, on the JVC I used (HR-J658) it's not. On decks up to like the mid 90s the rf amp was usually on it's own board, but on later decks the RF amp seems clumped together with other parts of the decoding chain on an IC so it may be harder to find a point to tap the signal after amplification.

    Also, you can use the composite inputs on the cx88 card, just have to specify the right input in the cxadc driver settings.
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  6. Thanks for the tip. I installed the card, built the driver from the GitHub repository, and used insmod to insert the module into the kernel. I rebooted and checked lsmod. Lsmod showed the module loaded before I rebooted but does not show it now. I guess I need to load it on boot and possibly blacklist the normal CX88 modules? I have little experience with using custom drivers on Linux, if anyone can help that would be great.
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  7. Mountains of gear vaporeon800's Avatar
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    You do need to blacklist the normal drivers. At the time I used cxadc, I followed the instructions in the then-current ld-decode documentation, which was a Google Doc. Can't link it at the moment.
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  8. I forgot about the Google document. I remember a guide on how to use the driver and dd to capture samples but couldnít find it. Iíll check and report back.
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  9. Awesome, thanks a lot.
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  10. I got the driver working. I ran the level adjustment tool using ./leveladj 31. I did a blank test recording connected to an unpowered s-video device. Besides the fact that my s-video cable sucks creating noise, the zero point is way off from DC center. Any suggestions?

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  11. I think I've put two and two together now. I hooked up a Roku box, ran the level adjustment tool with it turned on, chose level 19 with 0 low and high closest to 255, and captured a few fields of luma video. I opened this in Audacity and it looked good, but the lines were being clipped a bit at the top. At this point I realized "clipped" has to read 0. So I then chose level 6 which doesn't have as much dynamic range, but does not clip. Here are some Audacity screenshots, the first waveform being level 19 and second being level 6. My understanding of the goal is to get as much dynamic range as possible (low being 0 and high being closest to 255) without clipping. Do I have the gist of this?





    And here are both samples loaded respectively in the RawSource AviSynth filter running in Wine:




    With either case, the picture looks REALLY clean.
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  12. I hooked up a scope and capture card to the test point. I have to bottom out the volts per division to even see the RF envelope. I looked at the schematics for the main A/V block and the two amplifiers for the SP/EP heads are internal to the main IC. However, pins 78 and 79 break out to a capacitor that connect to what appears to be a switched amplified FM signal.

    https://imgur.com/a/E0392id
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  13. Yeah as noted you want to tap somewhere after the rf signal has been amplified.
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