Many people have the same question: why I can play AVI files on iPad sometimes, but not in most cases. According to Apple Official Website, the reason is iPad only supports this kind of AVI file: Motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 720 pixels, 30 frames per second, audio in ulaw, PCM stereo audio. When the imported AVI files are not encoded with the above codecs, you'll encounter issues.

To solve iPad won't play AVI issue, you'd better to convert AVI to MP4. Here is a guide to help you do this job at: http://www.faasoft.com/articles/how-...i-on-ipad.html