关于视频合成的调研

对于AVFoundation的理解

1. AVMutableComposition（音视频组合轨道）相当于一个容器，是总的音视频混合API

AVMutableComposition *mainComposition =[ [AVMutableComposition alloc]init];

2. AVMutableCompositionTrack  创建对应的音视频轨道

//可变音视频轨道添加一个 视频通道

AVMutableCompositionTrack*compositionVideoTrack = [mainComposition addMutableTrackWithMediaType:AVMediaTypeVideopreferredTrackID:kCMPersistentTrackID_Invalid];

//可变音视频轨道添加一个 音频通道

AVMutableCompositionTrack*compositionAudioTrack =  [mainComposition addMutableTrackWithMediaType:AVMediaTypeAudiopreferredTrackID:kCMPersistentTrackID_Invalid];