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Old 13th October 2014, 19:36   #21  |  Link
Retried Guesser
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Get access to an oscilloscope, or someone who uses one, and you can find the right pins with 5 minutes of probing around. Just be careful (you assume all risk of death by electrocution, etc etc)
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Old 14th October 2014, 12:20   #22  |  Link
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Originally Posted by SpOeK! View Post
One of the VCR that I'm using it's a Funai 25A-750. Following the same idea of finding the logic in charge of the Y/C mix and maybe intercepting the signals before this mix was carried on I've been able to get the service manual.

I've located the IC301 (LA71750EM) in charge of all these tasks. One pin (25) seems to carry "PB C OUT (Playback Chroma out?)" but sadly I still haven't found a similar pin for the Luminance. Best chance right now is pin 46 which is dubbed VCA-OUT but I'm just guessing without the proper datasheet.

I see Y before delay processing available on pin 46 (IC301 - Y/C combining is performed by IC internally) - Y delay is 1 line long easy to implement in software.


I would advise to use buffered signals (video opamps are cheap and widely available today).

Your current problem with S-Video capture can be solved by removing chroma signal in frequency domain from luma plane (defreq?).

Last edited by pandy; 14th October 2014 at 12:23.
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Old 16th October 2014, 08:29   #23  |  Link
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Thank you for the information, pandy.

All of this tinkering seems to be a bit out of my current skills so at the moment I'll stick with the composite output. Maybe in the future I will give this a shot.
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Old 14th November 2014, 17:29   #24  |  Link
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How do you use S-Video?
Is it through SCART?

As some S-Video (Like SCART in most cases) are not Real S-Video, but simply Composite.
And using that will result in much crosstalk (As Luma and Chroma is separated in S-Video, but if it's Composite in it it will be Luma = Luma/Chroma, Chroma = Luma/Chroma. And you can guess the mess.
Usually you get like a checkboard pattern with colored dots that falls down, yours is much more extreme, i am guessing it's some grounding issues.

Still all just a guess
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capture, composite, noise, s-video, vhs-c

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