Originally Posted by Alister Chapman
Bjorn, one thing to consider is that at low bitrates, like the ones used for HD TV broadcast, interlace images show more artifacts than progressive images. Mpeg 2 and Mpeg 4 both work much better with progressive images when the bandwidth is being minimised.
Mpeg2 actually handles interlaced material like progressive material, ie. it does NOT try to encode those interlace lines, but it sees the material as progressive. 30i becomes 60p, but at half the resolution.
So it doesn't matter to mpeg2 if the material is interlaced or not, the bandwidth is the same. As long as you flag it correctly, if you try to encode interlaced material as progressive then it will look very bad.