Depending on the file type, you may have to download a player.

 

The stock Android video player wants H264 encoded MP4 video, or 3gp. If you have Avi or other files, you'll either need to do a transcode or get an app like RockPlayer to handle more file types. 480x320 is the native video size.

The Optimus wants a lot of video to look decent, I'm finding 512k video is optimal, and 256k can pass, but will show some blockiness in H.264.

 

I need to add that I'm having issues with H264 AVC video transcoded with the free program FormatFactory, for reasons I'm not sure of, as of yet, as AVC video produced on the (paid) program I usually use has no issues at all. There's something going on with the basic encoder used by FormatFactory that the Android player doesn't like. Weird, as the FormatFactory video is fine everywhere else...it's got to be a codec issue.

 

You might also try qqplayer. I've tried rockplayer as well but qqplayer seemed to work better on several of my files.

 

I tried QQPlayer and I liked the features of battery life, clock and screen expansion. The downsides are that it has to be loaded in main memory and is a huge program (4MB+), and it loads in every media file as video...I have 3gp audio recordings on my card and it loads those as well. RealPlayer has folder types and can be moved to the card, which is a better fit for me...but thanks for the suggestion. I like the fact ArcMedia allows you to sort on folders only as well, rather than loading every video it finds on the card.