Hey! I just solved this problem and am very happy to share my working solution. The trick here is that two videos can have different fps. And we need to update the frameDuration AVMutableVideoComposition parameter of our AVPlayerItem in general, the code looks like this enum Const { static let perciseValue = 1000000 } struct SemgentModel { let framerate: Float let timeRange: CMTimeRange } var mySegments: [SemgentModel] = ..add segments var player: AVPlayer? func updateFramerateOfComposition(newRate: Float) { let mutableComposition = player?.playerItem?.videoComposition?.mutableCopy() as? AVMutableVideoComposition mutableComposition?.frameDuration = CMTime(value: CMTimeValue(1 * Const.perciseValue), timescale: CMTimeScale(newRate * Float(Const.perciseValue))) player?.playerItem?.videoComposition = mutableComposition } func setTime(time: CMTime) { if let segment = mySegments.first(where: { $0.timeRange.contains(time) }) { updateFramerateOfComposition(newRate: segment.framerate) } player?.seek( to: seekTargetTime, toleranceBefore: .zero, toleranceAfter: .zero) { ... } }