iphone ios AV Foundation

1.官方中文文档http://www.apple.com.cn/developer/iphone/library/documentation/iPhone/Conceptual/iOs精明的小丸子/MediaLayer/MediaLayer.html#//apple_ref/doc/uid/TP40007898-CH9-SW42.官方e文文档http://developer.apple.com/library/ios/#documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/00_Introduction.html