why are some mpeg video clips not playing as long as they actually are

I have been having this issue for a while now and I am sick of it. Any suggestions would be appreciated.
I have a few downloaded clips that are about 100MB, they are actually longer but only show up be 50s on windows media player. When I push the scanner halfway I can see more of the clip but it stops or freezes soon after. Anyone please let me know if they've encountered this problem. Thanks

 

Improperly joined files. It's common.

 

thanks for the reply.
what can I do about it. It was thinking that it was a codec problem at first. Is there any patch or decoder I can used to fix this. thanks

 

You could try demuxing in PVAStrumento, and then remuxing.
You could try re-encoding in virtualdubmod.
What are you going to do with the finished file? Just save it as avi, encode it for DVD, or what?

 

what do you use and how do you demux?

 

PVAStrumento. It splits the file into separate audio and video.

 

I've experienced the same thing though i use Zoom player to watch mpgs ive downloaded. The time shows up as for example 30 sec but the clip is 2 min long. In Zoom player the file plays all the way through but the time is incorrect. in the little research i've done, i think its a damaged mpg header. I'm still trying to figure out to fix the problem but right now as long i can watch the clip its okay. They're not not real important if you know what i mean. In the meantime try Zoom player its free and i like it better for watching clips. Media Player Classic also works better than the windows version