kjohn:
I don't think there are any scalers which will accept progressive input, although I could be wrong. The more common ones, such as the Faroudja NRS and Key Digital Leeza, only accept 480i for scaling. This is why you may see comments to the effect that DVD players should be set to interlaced output when being used with a scaler. They do a better job with 480i than the DVD player does with 480p.
I don't think there are any scalers which will accept progressive input, although I could be wrong. The more common ones, such as the Faroudja NRS and Key Digital Leeza, only accept 480i for scaling. This is why you may see comments to the effect that DVD players should be set to interlaced output when being used with a scaler. They do a better job with 480i than the DVD player does with 480p.