导出多个轨道：AVMutableComposition和AVAssetExportSession

Question

我有4个视频文件，我已对其进行编辑并将其添加到可变的作品中。 我正在尝试使用导出会话来导出文件，但是，当我导出时，仅导出了以下轨道列表中的第一条轨道

<AVAssetExportSession: 0x60800001da50, asset = <AVMutableComposition: 0x6080002240a0 tracks = (
    "<AVMutableCompositionTrack: 0x600000224ca0 trackID = 1, mediaType = vide, editCount = 8>",
    "<AVMutableCompositionTrack: 0x600000226da0 trackID = 2, mediaType = vide, editCount = 10>",
    "<AVMutableCompositionTrack: 0x60000023e180 trackID = 3, mediaType = vide, editCount = 3>",
    "<AVMutableCompositionTrack: 0x60000023e500 trackID = 4, mediaType = vide, editCount = 7>"
)>, presetName = AVAssetExportPreset1280x720, outputFileType = (null)

仅具有trackID = 1的第一条轨道被导出。 这是导出会话源：

   // Create path to output file
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:
                             [NSString stringWithFormat:@"ProcessedVideo-%d.mov", arc4random() % 1000]];
    NSURL *url = [NSURL fileURLWithPath:myPathDocs];

    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:batchComposition presetName:AVAssetExportPreset1280x720];

    NSLog(@"%@", exporter);

    exporter.outputURL = url;
    exporter.outputFileType = AVFileTypeQuickTimeMovie;

    [exporter exportAsynchronouslyWithCompletionHandler:^(void) {
        switch (exporter.status) {
            case AVAssetExportSessionStatusCompleted:
                NSLog(@"Completed");
                break;
            case AVAssetExportSessionStatusFailed:
                NSLog(@"Failed:%@",exporter.error);
                break;
            case AVAssetExportSessionStatusCancelled:
                NSLog(@"Canceled:%@",exporter.error);
                break;
            default:
                break;
        }
    }];

有谁知道如何使用导出会话将所有4条轨道导出到单个.mov文件？

Answer 1

您只能使用AVAssetExportSession导出到一个NSURL 。 如果要导出4个单独的文件，则必须导出4次。

Answer 2

感谢jlw的帮助。 我发现问题是我在可变的构图中添加了多个视频轨道。 相反，我应该做的是制作单个视频轨道，并将来自其他资产轨道的所有编辑应用于单个视频轨道。 似乎AVAssetExportSession将仅导出jlw指出的单个轨道。

摘要：

1. 创建可变的成分
2. 创建可变的合成音轨
3. 将资产轨道应用于合成（insertTimeRange）
4. 导出可变成分

Answer 3

我认为没有必要创建新的AVMutableComposition 。 而是只分配您的AVVideoComposition? 导出器的videoComposition属性。

guard let playerItem = getPlayerItem() as? AVPlayerItem else {
    return
}

let asset = playerItem.asset
let videoComposition: AVVideoComposition? = playerItem.videoComposition

let path = NSTemporaryDirectory().stringByAppendingFormat("/video.mov")
if NSFileManager.defaultManager().fileExistsAtPath(path) {
    do {
        try NSFileManager.defaultManager().removeItemAtPath(path)
    } catch {
        print("Temporary file removing error.")
    }
}
let outputURL = NSURL.fileURLWithPath(path)

guard let exporter = AVAssetExportSession(asset: asset,
                                          presetName: AVAssetExportPresetHighestQuality) else {
                                            return
}

exporter.outputURL = outputURL
exporter.outputFileType = AVFileTypeQuickTimeMovie
exporter.shouldOptimizeForNetworkUse = true
exporter.videoComposition = videoComposition // 👈

exporter.exportAsynchronouslyWithCompletionHandler {
    PHPhotoLibrary.sharedPhotoLibrary().performChanges({
        PHAssetChangeRequest.creationRequestForAssetFromVideoAtFileURL(outputURL)
    }) { (success: Bool, error: NSError?) -> Void in
        if success {
        } else {
        }
    }
}