在 AVMutableComposition 中更改音轨的音量

Question

我正在尝试将预先存在的视频与新录制的音频画外音轨道合并。用户可以设置两个音轨（属于视频的音频和新音频）的相对音量。

这段代码可以将其合并到一个新的视频文件中，但是我不知道如何调整音轨音量。我尝试了一些代码（已注释掉）但不明白如何将 AVMutableAudioMixInputParameters 与我已有的代码一起使用。

    static func mergeFilesWithUrl(videoUrl: URL, videoVolume: Float, audioUrl: URL, audioVolume: Float, completion: @escaping (URL?, Error?) -> Void) {

        let mixComposition: AVMutableComposition = AVMutableComposition()

        var mutableCompositionVideoTrack: [AVMutableCompositionTrack] = []
        var mutableCompositionAudioTrack: [AVMutableCompositionTrack] = []
        var mutableCompositionAudioOfVideoTrack: [AVMutableCompositionTrack] = []
        let totalVideoCompositionInstruction: AVMutableVideoCompositionInstruction = AVMutableVideoCompositionInstruction()

        let aVideoAsset: AVAsset = AVAsset(url: videoUrl)
        let aAudioAsset: AVAsset = AVAsset(url: audioUrl)

        mutableCompositionVideoTrack.append(mixComposition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: kCMPersistentTrackID_Invalid)!)
        mutableCompositionAudioTrack.append(mixComposition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid)!)
        mutableCompositionAudioOfVideoTrack.append(mixComposition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid)!)



        let aAudioOfVideoTrack: AVAssetTrack = aVideoAsset.tracks(withMediaType: AVMediaType.audio)[0]
        let aVideoAssetTrack: AVAssetTrack = aVideoAsset.tracks(withMediaType: AVMediaType.video)[0]
        let aAudioAssetTrack: AVAssetTrack = aAudioAsset.tracks(withMediaType: AVMediaType.audio)[0]

        do {
            try mutableCompositionAudioOfVideoTrack[0].insertTimeRange(CMTimeRangeMake(start: CMTime.zero, duration: aVideoAssetTrack.timeRange.duration), of: aAudioOfVideoTrack, at: CMTime.zero)
            try mutableCompositionVideoTrack[0].insertTimeRange(CMTimeRangeMake(start: CMTime.zero, duration: aVideoAssetTrack.timeRange.duration), of: aVideoAssetTrack, at: CMTime.zero)
            try mutableCompositionAudioTrack[0].insertTimeRange(CMTimeRangeMake(start: CMTime.zero, duration: aVideoAssetTrack.timeRange.duration), of: aAudioAssetTrack, at: CMTime.zero)
        } catch {

        }

        //TODO: how to set audio track volume

//        let audioMixInputParams = AVMutableAudioMixInputParameters()
//        audioMixInputParams.trackID = aAudioAssetTrack.trackID
//        audioMixInputParams.setVolume(0.0, at: CMTime.zero)
//        aAudioAssetTrack.inputParameters.append(audioMixInputParams)


        totalVideoCompositionInstruction.timeRange = CMTimeRangeMake(start: CMTime.zero, duration: aVideoAssetTrack.timeRange.duration)

        let mutableVideoComposition: AVMutableVideoComposition = AVMutableVideoComposition()
        mutableVideoComposition.frameDuration = CMTimeMake(value: 1, timescale: 30)

        mutableVideoComposition.renderSize = CGSize(width: 720, height: 1280)//CGSize(1280,720)


        //find your video on this URl
        let savePathUrl: NSURL = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/newVideo.mp4")

        do { // delete old video
            try FileManager.default.removeItem(at: savePathUrl as URL)
        } catch {
            print(error.localizedDescription)
        }

        let assetExport: AVAssetExportSession = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)!
        assetExport.outputFileType = AVFileType.mp4
        assetExport.outputURL = savePathUrl as URL
        assetExport.shouldOptimizeForNetworkUse = true

        assetExport.exportAsynchronously {
            switch assetExport.status {
            case AVAssetExportSessionStatus.completed:
                print("success")
                completion(assetExport.outputURL, nil)
            case AVAssetExportSessionStatus.failed:
                print("failed \(String(describing: assetExport.error))")
                completion(nil, assetExport.error)
            case AVAssetExportSessionStatus.cancelled:
                print("cancelled \(String(describing: assetExport.error))")
                completion(nil, assetExport.error)
            default:
                print("complete")
            }
        }
    }

Answer 1

这是我用来改变曲目的音量的代码：

    let audioMix: AVMutableAudioMix = AVMutableAudioMix()
    var audioMixParam: [AVMutableAudioMixInputParameters] = []

    let assetAudioFromVideo: AVAssetTrack = videoAsset.tracks(withMediaType: AVMediaType.audio)[0]

    let videoParam: AVMutableAudioMixInputParameters = AVMutableAudioMixInputParameters(track: assetAudioFromVideo)
    videoParam.trackID = videoAudioTrack!.trackID

    videoParam.setVolume(inputs.levels.videoVolume, at: CMTime.zero)
    audioMixParam.append(videoParam)

    audioMix.inputParameters = audioMixParam

    //...

    let assetExport: AVAssetExportSession = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)!
    assetExport.outputFileType = AVFileType.mp4
    assetExport.outputURL = savePathUrl as URL
    assetExport.shouldOptimizeForNetworkUse = true
    assetExport.audioMix = audioMix
    assetExport.videoComposition = videoComposition

    assetExport.exportAsynchronously { //...

在 AVMutableComposition 中更改音轨的音量

Change volume of audio track within AVMutableComposition

avmutablecomposition

avasset

swift

avmutableaudiomixinputparameters