ios - 在iOS SDK中以1.5播放速度保存视频

Question

我有一个录制的视频，我想将其另存为ios sdk中具有1.5播放速度(快进)的新视频。谁能建议我如何实现此功能？

谢谢
亚什什

Answer 1

AVURLAsset* videoAsset = nil; //self.inputAsset;

//create mutable composition
AVMutableComposition *mixComposition = [AVMutableComposition composition];

AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
                                                                               preferredTrackID:kCMPersistentTrackID_Invalid];
NSError *videoInsertError = nil;
BOOL videoInsertResult = [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
                                                        ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0]
                                                         atTime:kCMTimeZero
                                                          error:&videoInsertError];
if (!videoInsertResult || nil != videoInsertError) {
    //handle error
    return;
}

//slow down whole video by 2.0
double videoScaleFactor = 2.0;
CMTime videoDuration = videoAsset.duration;

[compositionVideoTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero, videoDuration)
                           toDuration:CMTimeMake(videoDuration.value*videoScaleFactor, videoDuration.timescale)];

//export
AVAssetExportSession* assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition
                                                                     presetName:AVAssetExportPresetLowQuality];