I can't speak to the XHA1S exactly, as I use it's bigger brother the XLH1. But while physically much different, electronically they are virtually identical cameras so the advice probably holds.
Within the cameras menu you can set/assign the DV output choices. I'm not in studio now so I can't check, but if memory serves the choices are something like automatic/SD/HD.
When set on automatic, the camera will play back whatever format the tape is shot on. But, if set to SD and you have an HDV recorded tape in the camera, when you play back it downconverts the firewire output to standard def (keeping in mind that it is still anamorphic widescreen).
Now, all that being said... that output conversion is for taped footage that has already been recorded, and just using the camera as a playback device. I don't know if the downcoversion will work when the camera is used for live output... but it might. On the plus side, at least there is a setting which you can try. I don't know if it will work, but it's better than no options at all.
You'll just have to make that menu adjustment... and give it a test drive.
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