Question

我正在尝试对我构建的AVMutableComposition进行音频编辑。

        var commentaryTimeRange = CMTimeRange(start: commentaryItem.startTimeInTimeline, duration: commentaryItem.timeRange.duration)
        if CMTimeCompare(CMTimeRangeGetEnd(commentaryTimeRange), composition.duration) == 1 {
            commentaryTimeRange.duration = CMTimeSubtract(composition.duration, commentaryTimeRange.start);
            commentaryItem.timeRange = commentaryTimeRange
        }
        // Add the commentary track
        let compositionCommentaryTrack = composition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid)
        let track = commentaryItem.asset.tracks(withMediaType: AVMediaTypeAudio).first!
        try! compositionCommentaryTrack.insertTimeRange(CMTimeRange(start: kCMTimeZero, duration:commentaryTimeRange.duration), of: track, at: commentaryTimeRange.start)

        let tracksToDuck = composition.tracks(withMediaType: AVMediaTypeAudio)
        var trackMixArray = [AVMutableAudioMixInputParameters]()
        let rampDuration = CMTime(seconds: 1, preferredTimescale: 2)
        for track in tracksToDuck {
            let trackMix = AVMutableAudioMixInputParameters(track: track)
            trackMix.setVolumeRamp(fromStartVolume: 1.0, toEndVolume: 0.2, timeRange: CMTimeRange(start: CMTimeSubtract(commentaryTimeRange.start, rampDuration), duration: CMTimeSubtract(commentaryTimeRange.duration, rampDuration)))
            trackMix.setVolumeRamp(fromStartVolume: 0.2, toEndVolume: 1.0, timeRange: CMTimeRange(start: CMTimeRangeGetEnd(commentaryTimeRange), duration: rampDuration))
            trackMixArray.append(trackMix)
        }
        let audioMix = AVMutableAudioMix()
        audioMix.inputParameters = trackMixArray

基本上我很想通过删除原始音量来在视频轨道上添加评论音频在输出中正确混合，但音频指令似乎被忽略当然audiomix被传递给AVPlayerItem，从调试我可以看到所有指令都存在并正确传递给它。

 func makePlayable() -> AVPlayerItem {
        let playerItem = AVPlayerItem(asset: composition.copy() as! AVAsset, automaticallyLoadedAssetKeys: NewsPlayerViewController.assetKeysRequiredToPlay)
        playerItem.videoComposition = videoComposition
        playerItem.audioMix = audioMix?.copy() as! AVAudioMix?
        if let overlayLayer = overlayLayer {
            let syncLayer = AVSynchronizedLayer(playerItem: playerItem)
            syncLayer.addSublayer(overlayLayer)
            playerItem.syncLayer = syncLayer
        }
        return playerItem
 }

我找到了一些答案，表明缺少曲目标识符的原因，或者有一个曲目和没有曲目的曲目之间的某种不匹配。
我的作品不使用任何曲目ID，加上Apple的AVEdit示例代码不使用它们并且它可以工作。

Answer 1

解决方案只是在添加评论音轨之前计算要追踪的曲目。

      let tracksToDuck = composition.tracks(withMediaType: AVMediaTypeAudio)// <- MOVE HERE, AT THE TOP

        var commentaryTimeRange = CMTimeRange(start: commentaryItem.startTimeInTimeline, duration: commentaryItem.timeRange.duration)
        if CMTimeCompare(CMTimeRangeGetEnd(commentaryTimeRange), composition.duration) == 1 {
            commentaryTimeRange.duration = CMTimeSubtract(composition.duration, commentaryTimeRange.start);
            commentaryItem.timeRange = commentaryTimeRange
        }
        // Add the commentary track
        let compositionCommentaryTrack = composition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid)
        let track = commentaryItem.asset.tracks(withMediaType: AVMediaTypeAudio).first!
        try! compositionCommentaryTrack.insertTimeRange(CMTimeRange(start: kCMTimeZero, duration:commentaryTimeRange.duration), of: track, at: commentaryTimeRange.start)

        var trackMixArray = [AVMutableAudioMixInputParameters]()
        let rampDuration = CMTime(seconds: 1, preferredTimescale: 2)
        for track in tracksToDuck {
            let trackMix = AVMutableAudioMixInputParameters(track: track)
            trackMix.setVolumeRamp(fromStartVolume: 1.0, toEndVolume: 0.2, timeRange: CMTimeRange(start: CMTimeSubtract(commentaryTimeRange.start, rampDuration), duration: CMTimeSubtract(commentaryTimeRange.duration, rampDuration)))
            trackMix.setVolumeRamp(fromStartVolume: 0.2, toEndVolume: 1.0, timeRange: CMTimeRange(start: CMTimeRangeGetEnd(commentaryTimeRange), duration: rampDuration))
            trackMixArray.append(trackMix)
        }
        let audioMix = AVMutableAudioMix()
        audioMix.inputParameters = trackMixArray

AVAudioMix音频闪避不起作用

1 个答案: