Video player ive downloaded several mp4 films to the nwz-a818 but can never play them the unit tells me the film is the wrong format,why is this and how do i fix the problem

That's correct...

i had the same issue until i met ipod video converter, it let any video playable on Ipod.

We can easily see that MP4 is a file container format, while H.264 is actually a video compression codec that requires a video container to host the encoded video. Although the file format shows in "MP4", you can still not play the because the parameters.

Here is the guide on how to convert H.264 to MP4 in detailed, where you can found solution to change the parameter too.

Make it clear what formats that your media player can support and use a video converter to convert your mp4 videos to the supported video format. You can try leawo video converter to do the conversion job.

This player supports MP4 and M4V but not all Mp4s are the same, some aren't compatible with certain mp3/video players. I've tried syncing several movies from my mac to my ipod only to find that they need to be reformatted b4 they can be transfered to my ipod. Try downloading a media converter program and reformating it as an MP4 or M4V. I know this is the same format but sometimes its just a matter of the MP3 player not liking that perticular version of MP4. Sometimes reformating the file to the same format can fix this. Also depends on the software, Try an Ipod MP4 format. Also Some MP4s are H.264 format which isn't always read by non-apple products, as this format is Hi-Def. Try using a basic, Non H.264 , MP4 format. I hope this helps. Oh, BTW, conversion software can also tell you the original format b4 you convert, including whether it was H.264 or not.