How i can change metadata (flag) w/o recompession stream with existing 720p25 avi encoded by Cineform to add 2:2 pulldown to every frame display twice (fake 720p50)? Thanks.

Why do you need to do this, as 25p in 50p project automatically add 2:2 pulldown when you turn frame blending off.

CineVision encoder accept as 1280x720 input only 50p.
I can change metadata in hex editor for mpeg2 but need solution for CF avi.
It is possible, David, manipulate with avi metadata header?

Unfortunately via the codec interface they are likely using, we can't lie about the number of frame and the frame rate. You will need to export to a new clip form Premiere as 50p,

1) open a 1280x720 p 50 project.
2) place your 25p clip on it.
3) Turn frame blend off for that clip.
4) Export to a new CineForm AVI.

Thank you, David! I'll try your recomendation.