size = bitrate * runtime
So if you want a smaller file you need to re-encode at a lower bitrate or reduce the runtime. @ 217MB (assuming that you meant Bytes, not bits), your source is probably already be compressed, so I don't like your chances of getting decent quality at 15MB's.
one:
If you are taking a 217MB and reduce it to 15MB, and it's already MPEG-4, you might as well not do it. You are looking at just one large block as a picture. That's going to be too low of a bitrate. You might want to try for like 45-55MB realistically
Two:
what machine are you using, Windows or Mac?
Three;
How long is the video clip?
Four:
You may want to check out the ImTOO Products (not free, and not going to give a link, u can google it) if you want to take anything other than a DVD and rip it down, that is, if you use it under windows. I have used it and it works OK, although, it's not fast. This is what you probably don't want to use if you are looking for free. Maybe someone else can provide a link to something like it, but free.
Five:
If you are under Mac, there is stuff like FFMpegX that works, it's a free software that you can get on sourceforge.
I?m wondering what u want to do after u cut AVI file to some pieces of 15M files,I guess u want to import them into portable player such as iPod, yes ? if that?s the case, u can make it by setting Start Time and Duration via ImTOO MPEG Encoder(as jackey recommends), u can also output iPod supported files.
I tried imtoo mpeg encoder after your suggestion. It may make it by setting Start Time and Duration, but Start Time and Duration function of the trial version is unavailable. If no one recommend me a free way, maybe I have to pay for this product. thanks.
Paying for the product is always good, but I am cheap, I end up finding a free one. Total Video Converter is a good one you can convert it to mpg which might make it smaller. I would also try AVI Splitter by 008soft
Explaining your intent may also prove to be helpful because loading 15 MB files into your Ipod vs uploading to YouTube are totally different stories. Also because it could turn out someone was trying to do the same things as you and tell you what they did or that someone might benefit from your final solution in the future
