[MEncoder-users] How does one interlace progressive content?

[Grozdan Nikolov]

Hi,

I'm trying to learn here the interlacing procedure along with the mencoder 
filters and I have a question about the tinterlace filter.

I have a 25fps progressive PAL DVD and I want to make it interlaced during 
encoding. Do I have to only add the tinterlace=4 filter to the filter chain 
or do I also have to provide a -ofps value?

I just did a small test with -vf tinterlace=4 on the progressive 25fps PAL DVD 
and during encoding I see that mencoder prints a huge amount of "duplicate 
frames". However, when playing the interlaced encode, everything looks fine. 
I can see the interlacing and there are no A/V issues.

Also, is the above procedure the same if you want to interlace a 23.976fps 
progressive NTSC content? what about 29.97fps progressive content?