https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/01_UsingAssets.html#//apple_ref/doc/uid/TP40010188-CH7-SW1
AVSimpleEditoriOS-视频的旋转,剪切,水印等
https://developer.apple.com/library/ios/samplecode/AVSimpleEditoriOS/Introduction/Intro.html
RosyWriter-视频加滤镜等
https://developer.apple.com/library/ios/samplecode/RosyWriter/Introduction/Intro.html#//apple_ref/doc/uid/DTS40011110
AVCam-iOS: Using AVFoundation to Capture Images and Movies-拍图片和视频
https://developer.apple.com/library/prerelease/content/samplecode/AVCam/Introduction/Intro.html