In Xcode which audio file types loop seamlessly?

So, I have read that if you want to make an audio sound play and loop, mp3 doesn't work well because it has a gap.开发者_高级运维 Are there any file types that work and when looped don't have a gap? If so, which types?

For me, .aiff works best. It loops seamlessly and has a small file size, but .wav works too.