使用 AudioMixInputParameters AVFoundation 为每个视频轨道设置多个音量在 Swift iOS 中不起作用

Question

我正在 Swift 中基于 Application 的 Video。根据要求，我必须 select 来自 Device Gallery 的多个 Videos，为每个 Video Asset 设置不同的 CIFilter 效果和 Volume 然后合并所有 Videos 并且必须保存 Final Video。作为输出，当我播放 Final Video 时 Video 声音 volume 应该相应地改变。

我已经将所有 selected Video Assets 合并为一个具有不同 CIFilter 效果的一个，但我的问题是当我试图为每个 Volume 设置时Video Clips 那就不行了。我正在为我的 Final Video 获取默认值 Volume。这是我的代码：

func addFilerEffectAndVolumeToIndividualVideoClip(_ assetURL: URL, video: VideoFileModel, completion : ((_ session: AVAssetExportSession?, _ outputURL : URL?) -> ())?){

        let videoFilteredAsset = AVAsset(url: assetURL)

        print(videoFilteredAsset)
        createVideoComposition(myAsset: videoFilteredAsset, videos: video)

        let documentDirectory = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]

        let url = URL(fileURLWithPath: documentDirectory).appendingPathComponent("\(video.fileID)_\("FilterVideo").mov")

        let filePath = url.path
        let fileManager = FileManager.default

        do {
            if fileManager.fileExists(atPath: filePath) {
                print("FILE AVAILABLE")
                try fileManager.removeItem(atPath:filePath)
            } else {
                print("FILE NOT AVAILABLE")
            }
        } catch _ {
        }

        let composition: AVMutableComposition = AVMutableComposition()
        let compositionVideo: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
        let compositionAudioVideo: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())


        //Add video to the final record
        do {
            try compositionVideo.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoFilteredAsset.duration), of: videoFilteredAsset.tracks(withMediaType: AVMediaTypeVideo)[0], at: kCMTimeZero)
        } catch _ {
        }

        //Extract audio from the video and the music
        let audioMix: AVMutableAudioMix = AVMutableAudioMix()
        var audioMixParam: [AVMutableAudioMixInputParameters] = []

        let assetVideoTrack: AVAssetTrack = videoFilteredAsset.tracks(withMediaType: AVMediaTypeAudio)[0]

        let videoParam: AVMutableAudioMixInputParameters = AVMutableAudioMixInputParameters(track: assetVideoTrack)
        videoParam.trackID = compositionAudioVideo.trackID

        //Set final volume of the audio record and the music
        videoParam.setVolume(video.videoClipVolume, at: kCMTimeZero)

        //Add setting
        audioMixParam.append(videoParam)

        //Add audio on final record
        do {
            try compositionAudioVideo.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoFilteredAsset.duration), of: assetVideoTrack, at: kCMTimeZero)

        } catch _ {
            assertionFailure()
        }

        //Fading volume out for background music
        let durationInSeconds = CMTimeGetSeconds(videoFilteredAsset.duration)

        let firstSecond = CMTimeRangeMake(CMTimeMakeWithSeconds(0, 1), CMTimeMakeWithSeconds(1, 1))
        let lastSecond = CMTimeRangeMake(CMTimeMakeWithSeconds(durationInSeconds-1, 1), CMTimeMakeWithSeconds(1, 1))

        videoParam.setVolumeRamp(fromStartVolume: 0, toEndVolume: video.videoClipVolume, timeRange: firstSecond)
        videoParam.setVolumeRamp(fromStartVolume: video.videoClipVolume, toEndVolume: 0, timeRange: lastSecond)

        //Add parameter
        audioMix.inputParameters = audioMixParam

        // Export part, left for facility
        let exporter = AVAssetExportSession(asset: videoFilteredAsset, presetName: AVAssetExportPresetHighestQuality)!
        exporter.videoComposition = videoFilterComposition
        exporter.outputURL = url
        exporter.outputFileType = AVFileTypeQuickTimeMovie

        exporter.audioMix = audioMix

        exporter.exportAsynchronously(completionHandler: { () -> Void in
            completion!(exporter, url)
        })

    }

在那之后，我再次使用一种方法使用 AVAssetExportSession 合并所有 Video Clips，我没有设置任何 AudioMixInputParameters。

Note: 当我使用 AVAssetExportSession's AudioMixInputParameters 在最终合并方法中设置音量时，然后 Volume 正在为完整 Video 进行更改。

我的问题：是否可以为每个Video Clips设置多个volume。请建议。谢谢！

Answer 1

这是我的问题的有效解决方案：

func addVolumeToIndividualVideoClip(_ assetURL: URL, video: VideoFileModel, completion : ((_ session: AVAssetExportSession?, _ outputURL : URL?) -> ())?){

        //Create Asset from Url
        let filteredVideoAsset: AVAsset = AVAsset(url: assetURL)

        video.fileID = String(video.videoID)

        //Get the path of App Document Directory
        let documentDirectory = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]

        let url = URL(fileURLWithPath: documentDirectory).appendingPathComponent("\(video.fileID)_\("FilterVideo").mov")

        let filePath = url.path
        let fileManager = FileManager.default

        do {
            if fileManager.fileExists(atPath: filePath) {
                print("FILE AVAILABLE")
                try fileManager.removeItem(atPath:filePath)
            } else {
                print("FILE NOT AVAILABLE")
            }
        } catch _ {
        }


        let composition: AVMutableComposition = AVMutableComposition()
        let compositionVideo: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
        let compositionAudioVideo: AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())


        //Add video to the final record
        do {
             try compositionVideo.insertTimeRange(CMTimeRangeMake(kCMTimeZero, filteredVideoAsset.duration), of: filteredVideoAsset.tracks(withMediaType: AVMediaTypeVideo)[0], at: kCMTimeZero)
        } catch _ {
        }

        //Extract audio from the video and the music
        let audioMix: AVMutableAudioMix = AVMutableAudioMix()
        var audioMixParam: [AVMutableAudioMixInputParameters] = []

        let assetVideoTrack: AVAssetTrack = filteredVideoAsset.tracks(withMediaType: AVMediaTypeAudio)[0]

        let videoParam: AVMutableAudioMixInputParameters = AVMutableAudioMixInputParameters(track: assetVideoTrack)
        videoParam.trackID = compositionAudioVideo.trackID

        //Set final volume of the audio record and the music
        videoParam.setVolume(video.videoVolume, at: kCMTimeZero)

        //Add setting
        audioMixParam.append(videoParam)

        //Add audio on final record
        //First: the audio of the record and Second: the music
        do {
            try compositionAudioVideo.insertTimeRange(CMTimeRangeMake(kCMTimeZero, filteredVideoAsset.duration), of: assetVideoTrack, at: kCMTimeZero)
        } catch _ {
            assertionFailure()
        }

        //Fading volume out for background music
        let durationInSeconds = CMTimeGetSeconds(filteredVideoAsset.duration)

        let firstSecond = CMTimeRangeMake(CMTimeMakeWithSeconds(0, 1), CMTimeMakeWithSeconds(1, 1))
        let lastSecond = CMTimeRangeMake(CMTimeMakeWithSeconds(durationInSeconds-1, 1), CMTimeMakeWithSeconds(1, 1))

        videoParam.setVolumeRamp(fromStartVolume: 0, toEndVolume: video.videoVolume, timeRange: firstSecond)
        videoParam.setVolumeRamp(fromStartVolume: video.videoVolume, toEndVolume: 0, timeRange: lastSecond)

        //Add parameter
        audioMix.inputParameters = audioMixParam

        //Remove the previous temp video if exist
        let filemgr = FileManager.default
        do {
            if filemgr.fileExists(atPath: "\(video.fileID)_\("FilterVideo").mov") {
                try filemgr.removeItem(atPath: "\(video.fileID)_\("FilterVideo").mov")
            } else {
            }
        } catch _ {
        }

        //Exporte the final record’
        let exporter: AVAssetExportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetHighestQuality)!
        exporter.outputURL = url
        exporter.outputFileType = AVFileTypeMPEG4
        exporter.audioMix = audioMix

        exporter.exportAsynchronously(completionHandler: { () -> Void in
            completion!(exporter, url)

           // self.saveVideoToLibrary(from: filePath)
        })
    }

Answer 2

我发现，导出预设为 AVAssetExportPresetPassthrough 的资产不会对输出量产生影响。当我尝试使用 AVAssetExportPresetLowQuality 时，成功应用了音量更改。

我希望它在某处有更好的记录:(

工作代码：

// Assume we have:
let composition: AVMutableComposition
var inputParameters = [AVAudioMixInputParameters]()

// We add a track
let trackComposition = composition.addMutableTrack(...)

// Configure volume for this track
let inputParameter = AVMutableAudioMixInputParameters(track: trackComposition)
inputParameter.setVolume(desiredVolume, at: startTime)

// It works even without setting the `trackID`
// inputParameter.trackID = trackComposition.trackID

inputParameters.append(inputParameter)

// Apply gathered `inputParameters` before exporting
let audioMix = AVMutableAudioMix()
audioMix.inputParameters = inputParameters

// I found it's not working, if using `AVAssetExportPresetPassthrough`,
// so try `AVAssetExportPresetLowQuality` first
let export = AVAssetExportSession(..., presetName: AVAssetExportPresetLowQuality)
export.audioMix = audioMix

使用多个 assetTrack 插入到同一个 compositionTrack 进行测试，为每个插入设置不同的音量。似乎有效。

使用 AudioMixInputParameters AVFoundation 为每个视频轨道设置多个音量在 Swift iOS 中不起作用

Setting multiple Volumes to each Video tracks using AudioMixInputParameters AVFoundation is not working in Swift iOS

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