Can you please give us specifics so we can better assist?

[ol]
[li]what apps(s) are you attempting to use to open the multimedia files?[/li]
[li]What are the file types?[/li]
[li]What medium are the file being retrieved from?[/li]
[/ol]

I don't use redhat so I am not quite certain about the functionality. But I am guessing that your system does not have the required audio and video codecs installed to run those files. I would recommend opening your package manager and searching for "codec", you should be able to find and install all necessary codecs to open your files.