无法用AVMutableComposition导出AVAssetExportSession

Question

这里是构图创作的一部分：

  AVMutableComposition* mixComposition = [[AVMutableComposition alloc] init];

  for (NSDictionary *track in tracks) {
    NSURL *url = [[NSURL alloc] initWithString:track[@"url"]];
    AVURLAsset *urlAsset = [AVURLAsset URLAssetWithURL:url options:nil];
    AVMutableCompositionTrack *firstTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio
                                                                        preferredTrackID:kCMPersistentTrackID_Invalid];

    [firstTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, urlAsset.duration)
                        ofTrack:[[urlAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]
                         atTime:kCMTimeZero
                          error:nil];
  }
  [self persist:mixComposition for:songId];

然后，我希望将集合保存在目录中，这样我就不必每次都下载它。

构图的输出如下：

"AVMutableCompositionTrack: 0x1c4a276a0 trackID = 1，mediaType = soun，editCount = 1"，"AVMutableCompositionTrack: 0x1c4a28560 trackID = 2，mediaType = soun，editCount =1“.

- (void)persist:(AVMutableComposition *) composition
            for:(NSString *) songId {

  NSLog(@"%@", composition);


  AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]
                                         initWithAsset:composition
                                         presetName:AVAssetExportPresetAppleM4A];
  NSString *path = [NSHomeDirectory() stringByAppendingPathComponent: songId];
  NSURL *url = [NSURL fileURLWithPath: path];
  exportSession.outputURL = url;
  exportSession.shouldOptimizeForNetworkUse = YES;
  exportSession.outputFileType = AVFileTypeAppleM4A;


  //   perform the export
  [exportSession exportAsynchronouslyWithCompletionHandler:^{

    if (AVAssetExportSessionStatusCompleted == exportSession.status) {
      NSLog(@"AVAssetExportSessionStatusCompleted");
      NSLog(@"Path : %@", url);
    } else if (AVAssetExportSessionStatusFailed == exportSession.status) {
      // a failure may happen because of an event out of your control
      // for example, an interruption like a phone call comming in
      // make sure and handle this case appropriately
      NSLog(@"%@", exportSession.error);

    } else {
      NSLog(@"Export Session Status: %ld", (long)exportSession.status);
    }
  }];

}

我所犯的错误：

错误Domain=AVFoundationErrorDomain代码=-11800“操作无法完成”UserInfo={NSLocalizedFailureReason=An未知错误发生(-12780)，NSLocalizedDescription=The操作无法完成，NSUnderlyingError=0x1c0a409f0 {Error Domain=NSOSStatusErrorDomain代码=-12780 "(null)"}}

Answer 1

您使用的路径必须包含需要导出的文件的内容类型，如下所示：

    let directory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first
    let audioTypeOutput = ".m4a"//type of your file, mp3, m4a for audio
    let exportPath = directory?.appendingPathComponent(name + audioTypeOutput)

希望能帮上忙！