Convert 720p25 back to 1080i50?

[RowanDDR]

I downloaded some English TV shows that are 720p25 (MKV). The framerate does not seem to be as smooth as the original broadcast, which I guess was 1080i50. Is there a way to convert the file back to an interlaced format so it plays as smooth as the original broadcast? In doing so, what if any quality is lost?

I want to author the file to an AVCHD disc ultimately.

Thanks in advance for any help.

[aedipuss]

no. half the motion samples have been removed. if you re-interlaced it all that would happen is the same frame would be split in 2 then re-combined by the tv. the re-encoding would cause loss of video quality to boot.

[jagabo]

You can try using motion interpolation techniques. They often generate weird artifacts though.