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我正在制作一个简单的视频编辑应用程序.我想为我的应用添加慢动作.我注意到AVMutableCompositionTrack类中有一个scaleTimeRange方法,所以我用它来实现我的目的.我发现scaleTimeRange在视频轨道上运行良好,但对音轨没有任何影响.这意味着音轨仍以原始速度播放.

关注是我的代码:

    CMTime insertionPoint = kCMTimeZero;

    double wholeDuration = CMTimeGetSeconds([asset duration]);
    double doubleDuration = CMTimeGetSeconds([asset duration])*2.0;
    CMTime trimmedDuration = CMTimeMakeWithSeconds(wholeDuration, 600.0);

    // Create a new composition
    self.mutableComposition = [AVMutableComposition composition];

    // Insert video and audio tracks from AVAsset
    if(assetVideoTrack != nil) {
        AVMutableCompositionTrack *compositionVideoTrack = [self.mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
        [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, trimmedDuration) ofTrack:assetVideoTrack atTime:insertionPoint error:&error];

        [compositionVideoTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero, trimmedDuration) toDuration:CMTimeMakeWithSeconds(doubleDuration, 600.0)];
    }
    if(assetAudioTrack != nil) {
        AVMutableCompositionTrack *compositionAudioTrack = [self.mutableComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
        [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, trimmedDuration) ofTrack:assetAudioTrack atTime:insertionPoint error:&error];

        [compositionAudioTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero, trimmedDuration) toDuration:CMTimeMakeWithSeconds(doubleDuration, …