I need to convert video data to 7.5 fps mpeg. By this i mean *real* 7.5 fps and not 7.5 at internal 30 fps ( thus cutting down the playtime by four) The only way i found is rather complicated and affects the quality because you have to recompress a few times.

I use Virtualdub to convert the video to 30 fps. Then i use Virtual dub again to decimate the frames of the 30fps video by 4. ( VirtualDub can decimate frames only by integers).The result is a 7.5 fps avi. Then i hex edit the avi back to 30 fps and convert this avi to 30fps mpeg with tnmpeg.

Is there a better way to do this ?

Btw if you wonder what i need 7.5fps mpegs for, it's a mpeg player i wrote for the gba

Just use AVISynth, you can open an MPEG with directshowsource and the audio with mpasource then do pretty much whatever you want with the framerate.

SelectEvery(4,0)
assumefps(30)

You're playing mpeg on a GBA?

Very, very brave.

great tool, thanks a lot !

Wait, your video is not already 30fps?

Then your command sequence should be different.

As a general method, you could use:

ChangeFPS(target)
or
ConvertFPS(Target)

This will prevent audio speed problems, which assumefps may cause.

<You're playing mpeg on a GBA?

<Very, very brave.

i assume you don't mean you have to be brave to watch mpg on a gba ,but to provide gba freaks with a free tool to watch simpsons episodes on their favourite machine :P

Because the quality is quite good when you have a frontlit gba.
I only have to get it a little faster... 12 fps would be cool.

Which mode are you using? Mode 3 might have drawing artifacts, 4 would limit your colors, and 5 would have a small resolution....

Well, best of luck to you regardless.

i use mode 5 scaled to fullscreen. when i have done some more optimizing i'm going to implement a mode 3 bilinear scaled dither function wich will look a lot better. It currently runs at stable at 7.5fps with (non mpeg) sound.