Video fields seems swapped - dropping quality when transcode

I’ve configured an HD channel transcoding. Source is 1080i 25fps, H264 AVC video, but as it is interlaced, it is moving smoothly in players and TV, you know, like 50fps.

However, the transcoded 1080 stream (I know I can transrate it or just pass it through, but I want to test transcoding quality) appears to be interlaced wrong, like its video fields were swapped. If, in transcoder’s Decode options, I turn on “Deinterlace source stream”, the picture is not interlaced anymore, but smooth movement is gone, it is true 25 fps now.

How can I achieve a proper interlacing and still that “50fps-like” movement?

This was handled in ticket #112083

Daren