I thought I would share my newfound understanding on how to properly deinterlace video when transcoding. In my case I am using mencoder to do the transcoding from mpeg2 -> mpeg4, but I suspect this applies to any scenario where you need to deinterlace. I believe this info is also very NTSC-centric.

I was having problems with jerky video using kerndeint on some shows. Sometimes it was subtle, sometimes significant. What I finally came to understand, after much reading and experimenting, is that you can't use a single deinterlace method on all shows. The two scenarios I have encountered so far are:

1. Source show was shot at 29.97fps and can be properly deinterlaced using "kerndeint", "linear blending", etc. It appears that all news and sports broadcasts fall into this catagory. Some other programming is also done this way. For example, the sitcom "The Nanny" appears to have been produced this way.

2. Source show was shot with film at ~24 frames/second and can be properly deinterlaced using "filmdint". The final deinterlaced stream will be at ~24fps, not 29.97fps. It appears that moves and most other shows are done this way. My experience is that the TV series "JAG" and "Friends" are both best deinterlaced using this methodology.

I have not found any way to automatically determine which method works best. I would be interested in any additional inisghts others may have on this topic...

marc