saturnu / gcvideo

GameCube Digital AV converter

GCVideo

GCVideo is a small series of devices capable of converting the GameCube's Digital Video port signals to standard video signals without using the custom chip in the original component video cable. There is currently just on device, GCVideo Lite, which outputs analog RGB or Component video signals. It has also been adapted to be used as an RGB DAC for the N64 since the board was already done.

The schematics and layout are in the Hardware directory and the HDL project is in the HDL directory. Each directory should contain README.md files with further information.

Mini-FAQ

1. I want one, how much is it?
   I do not sell any hardware. Since this is an open-source project, other people will probably offer ready-made boards or modding services.

2. But why don't you just sell it?
   Building hardware to be sold is a lot of work and requires much time that I'd rather use for something more interesting. Furthermore, the local laws require quite a bit of paperwork and investment to legally sell electronic devices that you build and I'd prefer not to deal with all of that.

3. You said your prototype came from OSHPark, so you have at least three boards. Can't you sell me one of them?
   No, they're all accounted for already.

4. Why analog instead of HDMI?
   I had this project on my bench for a few months and the HDMI version started to suffer from featuritis, so I decided to do an analog-output version first to stop people from paying the insane prices of the original cables. I have a version of the code that runs on an Atlys board (FPGA development board with HDMI outputs) that can convert the GameCube's video to HDMI (technically it's just DVI), but it is currently suffering from featuritis and lack of time for further development. Additionally I'm not confident enough in my PCB layout skills to create a board with 135MHz high-speed serial signals on it. If any small and cheap Spartan6 dev board with an HDMI output connector becomes available, I might adapt my code to it and release it.

   If you want to try to build an HDMI/DVI-output version of GCVideo yourself, just ask me for the code - it needs a bit of cleanup, so it's not in the repository yet. If you want to figure it out yourself I'll give you the hint that via DVI the monitor can tell the difference between black pixels and the blanking area and the GameCube rarely outputs the full 720x480/x576 pixel image that is in the specs. Some displays don't mind, others refuse to show anything.

5. Why did you use that weird Video-DAC, it's a non-stock part at Digikey!
   It wasn't when I designed the board some months ago... Instead it was the cheapest 24-bit video DAC available. It shouldn't be hard to adapt the design to a different DAC as long as it has 24 bit parallel input and a single-pumped clock. For YPbPr output, the DAC also needs to be able to generate a small offset on the Y line so that syncs can be generated below the blanking level.

6. Uh, it says XO2-256 in the schematic, but XO2-640 in the BOM. Which is the correct one?
   The original plan was to use an XO2-256, but adding the color space conversion for RGB output increased the size of the design too much. It was left as an XO2-256 in the schematic to ensure only pins available on that chip are used, so a slightly cheaper Component-only version can be built.

7. What about linedoubling?
   The FPGA used in the design is the smallest one that could fit everything, but it does not have enough BlockRAM available to store everything needed to generate a linedoubled picture. There is a larger, footprint-compatible FPGA (XO2-1200) available that should have enough resources to add at least simple linedoubling. On my HDMI prototyping system I have a working linedoubler that takes 240p/288p to 480p/576p, but I wasn't able to generate a working output timing from interlaced input signals. Additionally, simple linedoubling doesn't look very good for interlaced signals anyway, so the only reason I see to include it would be to increase compatibility with devices that accept 480i, but not 240p.

Licence

Copyright (C) 2014, Ingo Korb <[email protected]>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

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