61 lines
2.5 KiB
Markdown
61 lines
2.5 KiB
Markdown
# OSDSwitch
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FF-OSD Video Switcher for clean video output
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This is a small board with a high bandwidth video switching chip
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on it. The idea is that this sits in between the video generation
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circuitry and the video output socket of your Amiga (or similar
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computer) and is controlled by the On Screen Display signal from
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a modified Gotek (see [keirf/flashfloppy-osd](https://github.com/keirf/flashfloppy-osd).
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Normally the output of the OSD mod is just blasted unceremoniously
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over the green (or channel of your choice) signal, overpowering the
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circuitry in the receiving display system to give a green tint where
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the text is.
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This is not great. It's crude, and doesn't always work right, and
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the results are often less than desirable.
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This small board is the answer. It actively cuts out the normal
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video signal when the OSD text should be displayed, and replaces that
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video signal with a statically defined colour of your choice (configured
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by 3 jumpers) to give a crystal clear OSD that is embedded within the
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video stream, not overlayed on top of it.
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I developed this board because I use an Extron video scaler connected
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to my Amiga for both video capture while livestreaming and for display
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on a modern TFT screen. But the traditional overlay setup really didn't
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work with the Extron. Everything went pink:
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And so this board was born. The ADG1633BCPZ looked to be the ideal
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chip, with more than enough bandwidth for a video signal (one of the
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intended applications for this chip), and three channels, the board
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was pretty simple to design. And I think you'll agree the results
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are much nicer:
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(This image is from before I tweaked the resistor values a little,
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so the OSD is a bit darker than I would have liked).
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Installation is reasonably simple. For the Amiga 500 (R6):
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* Lift the side of the three ferrite beads by the video connector that is facing
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towards Denise (where you would normally solder the OSD wire to.
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* Connect three wires to where they were soldered
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* Attach the three wires to the INPUT side of the board's R G and B pins.
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* Solder the ferrite beads you just lifted one side of to the output
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R G and B pins
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* Connect a 5V and GND signal from somewhere suitable
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* Connect the signal from your OSD generator to the IN pin.
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Choose the colour you want with the jumpers (bonus hack: if you use resistors
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instead of jumpers you can get a wider range of colours to choose from).
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And here it is installed in my Amiga:
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