iPod have a lot of limitations when you want to covert your videos into iPhones or iPods. iPad doesn’t.
Thanks to the A4 Chipset. iPad can decode more complicated videos.
THE MOST IMPORTANT THING:
Change the dimensions to 1280 x720 HD (that’s 720P) when you encode it in H.264 .
The format iPad accepts
H.264 video up to 720p, 30 frames per second,
Main Profile level 3.1 with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats;
MPEG-4 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second,
Simple Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats;
Motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 720 pixels, 30 frames per second, audio in ulaw,
PCM stereo audio in .avi file format
Basically if you are using QuickTime 7 ( with / without x264 encoder),
When you see the window below => Options
Here is the most important part, Change the dimensions to 1280 x720 HD (which is 720P that iPad support)
Enjoy the videos on iPad.