Which model Yamaha?
How do you watch movies on your iPad?
Usually if you plug the HDMI into the receiver, then the receiver into the TV, you can get the digital signal to your speakers that way. If your iPad only has stereo as a source file, you can use Dolby Pro Logic II if your receiver has it (converts stereo to quasi-5.1). iirc the CineXPlayer from Dolby does 5.1 out via iPad using Xvids. And if your receiver does AC3 decoding, you can supposedly do Dolby 5.1 out with the Apple adapters. Variety of options out there, depending on how what you'd like to do.