VGA Output
The majority of this evening was spent constructing a simple converter that takes output from the Xbox and converts it into mostly spec VGA.

The Xbox has a video encoder chip that takes the raw digital input and converts it to (usually) composite video, although it also outputs luminance and chrominance for S-Video, as well as both current HDTV standards. From a combination of signals from all of these formats, a VGA signal can be formed. The problem is that the sync signal for the whole picture is encoded within the Green channel. This is not VESA-compliant.

The solution to creating a more-or-less VESA compliant signal is to use a video sync splitter chip. In this case, the National LM1881N was used. The input to the chip is the Green channel and the outputs are the horizontal and vertical sync signals, which go directly to pins 13 and 14 on a VGA connector.

While the rest of the PCB is mostly pass-through for the video signals and their ground lines, there Xbox also outputs audio through the same connector as video. Therefore, there is a stereo headphone jack, and it works surprisingly cleanly.

Unfortunately, the video portion of the converter is not ideal. It was expected from the start that there would be a slight greenish tint, since the colours are not weighted for VGA display. However, the green tint is quite heavy wherever other colours are not displayed. Also, there are occasionally some sync issues. Upon investigating the completed circuit, it appears that the resistor is approximately half as resistive as it is supposed to be. Perhaps the resistor is faulty. This may explain some of the issues, so it will be replaced at some point in the near future.