Amiga 1000 connected to framegrabber via Composite, RGB, VGA or other cables

[drHirudo]

Hello,
I am trying to connect my Amiga 1000 to Blackmagic Decklink 4K Extreme 12G framegrabber, that has HDMI, S-Video, Composite and Component inputs.

First I've tried with my RGB to SCART cable connected to SCART to HDMI converter upscaler connected to the Decklink via HDMI, but I was only getting sound and very dark shadowed picture, which is unusable, so I didn't record it.

Then I've tried with AV&S-Video to HDMI convertor upscaler, connected to the Decklink via HDMI and I got acceptable picture, but the built-in deinterlacer makes the picture to flicker, even when there is no interlaced signal. Here is my test result:

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Then I've tried directly linking the Amiga 1000 to the Decklink with the use of Breakout cable and Composite-in with Cinch cable, but I came to unsatisfactory result:

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I still want to get the best possible results, so what are my other options now?

Shall I buy OSSC and try with it to the HDMI input?

Or buy RGB to VGA converter and try with VGA to HDMI convertor that I have?

Or try to fix the RGB to SCART and grab with the SCART to HDMI converter.

The framegrabber is very picky about the resolutions and screenmodes and even slight difference makes it to not grab any picture, or give bad results. Till now I still haven't figured how to framegrab Apple PowerBook G4 and MacMini G4 with it, either under MacOS X or Morphos, so it is very hard to adjust the signal to be like from camera or Video/DVD player.

Here is the framegrabber that I am using:
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