Today’s high-def broadcasts are done in either 1080i or 720p, and there’s little or no chance they’ll
jump to 1080p any time soon because of bandwidth issues and Blue Ray is interlaced format too.
What happens when you feed a 1080i signal to a 720p TV?
The 1080i signal is scaled, or downconverted, to 720p. Nearly all recent HDTVs are able to do this.
What happens when you feed a 1080i signal to a 1080p TV?
It’s converted to 1080p with no resolution conversion. Instead, the 1080i signal is “de-interlaced” for display in 1080p. Some HDTVs do a better job of this de-interlacing process than others, but usually the artifacts caused by improper de-interlacing are difficult for most viewers to spot.
AE’s deinterlacer is very poor quality compared to other methods, hardware based or third party tools.