I have transferred a targa sequence with alpha to my Vision switcher which I want to play out in Still Store channel 1, but when I play out the sequence it does not key. I have tried setting the alpha channel in the source settings to Still Store channel 1, but then it won't play out the sequence. Do I have to have an entirely separate targa sequence that is just the alpha or is there some way to play out my original sequence with the alpha information built-in?