如何将视频长度设置为原始视频长度的 3/4 倍？

Question

我想导出比原始视频多 3 倍的视频（同一视频重复 3 次）。这意味着 2 秒的视频将是 6 秒。这怎么可能？

我已经实现了导出视频并将其保存在 cameroll 中。所以请建议我最好的方法。

Answer 1

AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

/*******************Code for increase video length*****************************************/

AVAssetTrack *clipVideoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:clipVideoTrack atTime:kCMTimeZero error:nil];
CMTime videoLength = videoAsset.duration;
if(self.isVideo){
    [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:clipVideoTrack atTime:videoAsset.duration error:nil];
    videoLength = CMTimeAdd(videoAsset.duration, videoAsset.duration);
}
[compositionVideoTrack setPreferredTransform:[[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] preferredTransform]];

//slow down whole video by 2.0
double videoScaleFactor = scalfactor;
CMTime videoDuration = videoLength;
[compositionVideoTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero, videoDuration)
                           toDuration:CMTimeMake(videoDuration.value/videoScaleFactor, videoDuration.timescale)];

CGSize videoSize = [clipVideoTrack naturalSize];

/******************* End Code *************************************************************/

如何将视频长度设置为原始视频长度的 3/4 倍？

How to set video length 3/4 time more then original?

iphone

objective-c

avfoundation

ios