Truly or not truly interlaced source?

[Eyael]

Could anyone be kind enough in explaining how you can tell the difference (I mean visually) between interlaced and non interlaced video sources?

I've tried to encode a PAL interlaced DVD (not a TV movie) as if it were a progressive source and the result was OK (not perfect, just okay and I've used a 905kB/s bitrate).
Then I've set the Desinterlace filter in ffdshow video decoder to see if it would produce a difference, but I could not see any. So my question is was the source truly interlaced? GSpot says it is and so does DGIndex (I've tried VOBs without the logo). So how can you really tell?

And when a source is truly interlaced, which desinterlacing method should I use before encoding : GordianKnot's filters or XviD's interlaced encoding mode?
A million thanks for letting me know.

[jggimi]

See www.doom.org/ivtc-tut.htm for guidance on interlaced and telecined material with GK. The software discussed is a little out-of-date, but the content is still quite usable. Most of the discussion is about telecined content, but there's a PAL section there as well you should find helpful.

[Eyael]

Thank you. By the way you got the URL wrong (forgot the "9") but I'm managed to sort it out. For those who would like to get the info it should read

http://www.doom9.org/ivtc-tut.htm