The final format I checked was Video. The box advertises support for MPEG-1, MPEG-2, MPEG-4 and DivX 4 and 5, but like many things, it's not quite as easy as that. I'm no expert in the matter, but I know that at least MPEG-2 and MPEG-4 come in different types. For example, I found a site that advertised MPEG-2 test streams that manufacturers can use to test their MPEG-2 decoders. But it turned out they were MPEG-2 transport streams, and were incompatible with the MP115.
I created a MPEG-4 movie on my iBook using iMovie, but it too was incompatible because it wrapped the video stream for use in Quicktime. A NETGEAR representative verified that only MPEG-4 movies wrapped in AVI format would be playable. But even then, there are incompatibilities because there's more than one way to do MPEG-4 encoding.
Despite using several programs ( Quicktime Pro , VLC , HandBrake ) to generate MPEG-4 AVI files, I was never able to create an MPEG-4 movie that was playable on the box. One of my movies even caused the box to lock up hard, requiring a power reset. Given more time, I suspect I could have found the magic encoding incantation, because NETGEAR supplied me with some sample MPEG-4 AVI files that did play correctly.
I had better luck with MPEG-2 files. My best source of MPEG-2 movies were DVDs I had created with iDVD. Internally, DVDs use MPEG-2 encoding, but the video is wrapped in a VOB format (DVD Video Object) that includes information about chapters, alternate tracks, etc. A file with a .vob extension is not recognized by the NETGEAR server, but I found that if I renamed a file from *.vob to *.mpg it was usually playable. The decoder must be smart enough to skip past non-recognized data until it gets to MPEG-2 data.
Commercial DVDs are another matter. Commercial DVDs are normally encrypted, so their VOB files will not play unless the encryption is removed. I extracted and unencrypted a VOB file from one of my DVDs and the result played fine with one exception. The DVD was in wide-screen format where the video was "letterboxed" on the screen with black bars on top and bottom of the picture.
However, when I viewed the video on the MP115, the picture was stretched vertically to take up the whole screen where the black letterbox bars had been. Fortunately, a quick check of the preference menu gave an option to allow the video to play without stretching. Once this was set, the video displayed properly.
My experience with MPEG-1 video was the smoothest because all of my MPEG-1 samples played properly. So MPEG-1 appears to be the safest bet, for trouble-free video playback on the MP115, but that means sacrificing a lot of quality. Note that I didn't try to play DivX 4 or 5 files.
One feature that seemed a bit odd with movie playback was the way it automatically moved on to the next movie in the list when the first was complete. Maybe this would be fine for music and slide shows, but after viewing a 2 hour movie, I wouldn't want the box to just automatically start up a new one.
Tip: While researching the playback of video on the device, I came across an entire forum devoted to tricks, tips and experiences in using the same media server and decoder in use on the MP115.