如何在iOS中使用AVPlayer實現4.0的播放速率？

Question

player.rate = 4.0不適用於我。

是否用AVPlayer實現4.0的比率是一個好方法，還是有更好的方法？

Answer 1

使用[AVComposition scaleTimeRange:toDuration:]來產生快動作AVAsset。

float rate = 4.0; 
AVAsset *asset = [AVAsset assetWithURL:someURL]; 
AVMutableComposition *composition = [AVMutableComposition composition]; 
NSError *error = nil; 
[composition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) 
        ofAsset:asset 
         atTime:kCMTimeZero error:&error]; 
[composition scaleTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) 
       toDuration:CMTimeMultiplyByFloat64(asset.duration, 1/rate)]; 
AVPlayerItem *playerItem = [AVPlayerItem playerItemWithAsset:composition]; 
AVPlayer *player = [AVPlayer playerWithPlayerItem:playerItem];