[FFmpeg-user] input to YADIF filter

[Human Being]

 yes, with the enable option things got a bit better, although now i don't understand what n actually is. it's supposed to be a sequential frame number, but when i try

-vf "yadif=enable='between(n,0,1)'"
then the first two frames won't be deinterlaced. instead,

-vf "yadif=enable='between(n,2,2)'"
gets the 1st frame deinterlaced,

-vf "yadif=enable='between(n,3,3)'"
gets the 2nd frame deinterlaced, and

-vf "yadif=enable='between(n,2,3)'"
gets both of them deinterlaced.

earlier, i ran the following command

ffmpeg -t 30 -i VTS_01_3.VOB frames/%04d.png

to look at the frames and manually pick those interlaced. i saw that the first two frames were interlaced [0001.png and 0002.png], and the next frames with combs were on images 0116.png and 0117.png. so, 1 in snapshots corresponds to 2 as n, and 2 to 3. then, much to my surprise, i found out that n values for the next interlaced pair [116 and 117] were 96 and 97. does it make sense to anybody? if yes, i'd love to read your explanation. if not, any suggestions are welcome.