I want to share this for anyone who might search for it in the future to save them some time.
The VideoData DAC-100 needs a 5V power supply (center pin positive) that can delver AT LEAST 6W of power.
This means that 5V 1A will NOT work.
It may look like it is working, but it will randomly reset the input source.
I found this out because the DC adapter that I was using just stopped working. To replace it, I took an old usb cable and connected to the end of the broken DC adapter (keeping center pin positive).
I then plugged into a USB power supply that happened to be 5V, 1A. (I didn't check the amps at first - just assumed it would be enough).
Everything looked like it was working, but I just spent over an hour trying to figure out why it would just reset itself once the video started playing. Tried replacing different wires, sending video through different devices, and it would just reset itself either immediately or after a few seconds of playing a video through it.
Finally, I looked at the adapter and saw that it was only "1A".
I changed it with a more powerful USB power adapter, and voila. It's been staying on and working consistently.
I now wonder if the old power adapter that I had, that recently stopped working, was causing problems before, as it would reset itself every once in a while. I always assumed it was a problem with the video coming through, but now I suspect that it was power-related all along.
So, make sure your DAC-100 is getting the power it needs!