为.mov文件目标C

Question

我试图生成缩略图并将其保存到文件中。这是我的代码。

   AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:object[@"path"] options:nil];
     AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
     NSError *err = NULL;

     CMTime requestedTime = CMTimeMake(1, 60);     // To create thumbnail image

     CGImageRef imgRef = [generator copyCGImageAtTime:requestedTime actualTime:NULL error:&err];

     NSLog(@"err = %@, imageRef = %@", err, imgRef);

     UIImage *thumbnailImage = [[UIImage alloc] initWithCGImage:imgRef];

     CGImageRelease(imgRef);

     NSString* path = [NSHomeDirectory() stringByAppendingString:@"/Documents/myImage.png"];
     BOOL ok = [[NSFileManager defaultManager] createFileAtPath:path
                                                contents:nil attributes:nil];
     if (!ok)
     {
       NSLog(@"Error creating file %@", path);
     }
     else
     {
       NSFileHandle* myFileHandle = [NSFileHandle        fileHandleForWritingAtPath:path];
       [myFileHandle writeData:UIImagePNGRepresentation(thumbnailImage)];
       [myFileHandle closeFile];
       resolve(path);
     }

但是我收到了这个错误：

 Code=-11822 "Cannot Open" UserInfo={NSLocalizedDescription=Cannot Open, NSLocalizedFailureReason=This media format is not supported.}

有什么想法？