Video Player Issues

[Wogenst]

Ok. Here is one that has me stumped. Sometimes I will DL a 3gp or mp4 file from the internet and save it. When I go to play it in any media player on the phone I get a message that the file format is unsupported. I thought that the customary format for mobile phones was 3gp. Am I missing something in trying to play these files?

Thanks again..