Recently, I have found this article as below. Hope this will help all of you.

According to the Wikipedia figures, more than 25 million units of PSP have been shipped worldwide already. Lots of PSP users who are hungry for more content to put onto their PSP have to admit that downloading movies onto PSP via the internet is the easiest and fastest way.
The only problem is PSP can only support MP4 video formats (H.264/MPEG-4 AVC) while most movies and videos on the internet are the format of WMV, AVI or DivX. Chances are you have at least a small collection of videos on your computer hard drive – and those videos probably won't be supported because PSP essentially does not have "WMV playing" or "AVI playing" features!
Therefore, you will need a PSP video converter to convert the videos to be compatible with the PSP.
I’m using the ImTOO PSP Video Converter but other PSP conversion software should do the job as well.
Due to its wide LCD screen, playing video on the PSP is a little different, and, to get the best quality, you are supposed to follow certain settings.
For video settings, you will need to make video resolution at either 368x208 or 480x272. The video bit rate should be at 400, 512 or 768 kilo bits per second (Kbps). The frame rate should be at least 29.97 frames per second so there is no shuttering when playing video.
For the audio specification, it is almost a criterion selection. The sample rate should be at 24 KHz and the audio bit rate at 64, 96, 128 or 160 kbps.
And also, it offers a free tool for your movies to PSP transfer - PSP Video Manager, which can be handled so simply to put video on PSP.
I would highly recommend downloading a PSP video conversion tool rather than use a generic video converter to do the video to PSP conversion as it is easier and you do not need to remember these technical parameters.