Question about avi framrate

[goldrake72]

Hi,
i've an avi file that runs at 23,97 fps (after inverse telecine from
ntsc at 29,97 fps) and its length is 60 seconds.
Is there a program to change only the framerate of the avi
file but not the length??
I've tried avi framerate changer but after patching the file
the length of it gets shorter in time.
I want to keep the same length but at 25 fps.
Is there something to change the framerate in the avi header but
keeping the same lenght??

thanks in advance

[stephanV]

well yes, by adding duplicates or interpolations of frames... but that would require re-encoding the file. and it causes jerky playback.

[goldrake72]

ok...but is there a program to edit or change
the parameters in the avi header??
every program i've tried when it's time to change
the frame rate it changes also the whole length..
i want different framerate but same length.

orginal ntsc 29.97 = 60 seconds

inverse telecine 23.97 = 60 sec

new pal file 25 = 60 sec

is there a program to change only the framerate but not the length??
i mean..to patch the avi header..in this case avi framerate
changer is useless...

thanks in advance

[stephanV]

what you want is not possible, you cannot change the framerate without affecting the length if you dont add frames somehow.

the equation is videolength = number of frames/frame rate

changing one will always affect the other... thats how maths works :)

[goldrake72]

ok....thanks for your time!

my problem was that if i convert from ntsc to pal
i have to perform inverse telecine.
From 23.97 to 25 i have to speed up the video and not only the video
but also the audio....
the pal video file is shorter in video and audio....but
at this point who cares if the length is shorter....
i don't think i'll see the difference watching the file
with a dvd player and a tv set...

[scharfis_brain]

it is possible doing a FILM conversion from NTSC to PAL without a speedup.

there are several methods availabe using avisynth. but all of them RERQUIRE reencoding

1) just inserting a dupe every 25 frames (heavy jerks)

2) insert two fields per sec. film becomes combed -> interlaced encoding nesessary (twice a scond, you'll get a slight stutter)

3) blend neighboring frames and use them as in/between fields -> ghosting, but nomore any stutter, interlaced encoding required

4) use motion compensation, to interpolate 23.976 fps up to 25 fps
-> progressive Film, but motion artifacts, due to motion compensation will appear.

5) the PAL-Speedup. progressive. just 5% faster, audio gets pitched about a half tone upwards

[bobmaster]

I think windows media encoder 9, will do frame rate conversion without changing length of the file.

Downside – you will have to encode to a windows format also it is buggy and slow