Please clarify. The original plays fine-where? TV or monitor? You're viewing the ripped file on which- a computer monitor, or did you burn it to DVD and are seeing the jaggies on your TV?
Normally, you only deinterlace to optimize viewing on a computer monitor. Interlaced recordings will have jaggy lines on a monitor, sometimes almost invisible, sometimes very annoying. Movement exacerbates the jaggies.
It's highly unlikely an original, pressed, DVD would be deinterlaced. :eek: Encoded badly, yes, occasionally. BTW, progressive source video from film is encoded on DVD as interlaced field pairs. A progressive player merely reinterleaves to recreate the progressive video.
Now, unless I've misunderstood your question entirely, or am all wet, (Often wrong, never in doubt! ), here's what I'd do:
Try burning one to a DVDRW and test it on your TV. And for your computer get a decent software player like Media Player Classic or Videolan.