Objective-c how to add filter to an existing video like Instagram Application?

I'm trying to add filter to video after recording it, just like Instagram. After searching for a way I found GPUImage, but that didn't solve it since in this code the video is being written to directory before displaying it (causing delay):

//Setting path for temporary storing the video in document directory
NSURL *movieURL = [self dataFilePath: @"tempVideo.mp4"]; // url where we want to save our new edited video

Is there a way to preview the filtered video before saving it in order not to take time? If so, how it is done?

Also, I found in the apple documentation about CIFilter but still can not find a way that states how to add filters to the video.

In addition, that there are some codes but written in swift.

Thanks in advance.

Solution

I couldn't find a way to stop the delay that is happing with the GPUImage. So I tried working with the SCRecorder.

What I have done is:

[_player setItemByUrl:videoURL];

instead of:

[_player setItemByAsset:_recordSession.assetRepresentingSegments];

by this way I'm able to play and add filter to an existing video just like Instagram.

To export the video with the chosen filter I used this code:

 - (void)saveToCameraRoll {

  NSString *fileName = videoURL.lastPathComponent;
  NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *docsDir = [dirPaths objectAtIndex:0];
  NSString *videoPath = [NSString stringWithFormat:@"%@/%@",docsDir,fileName];
  NSURL *urlPath = [NSURL fileURLWithPath:[NSString stringWithFormat:@"%@", videoPath]];

  NSURL *assetUrl = urlPath;
  AVAsset *asset = [AVAsset assetWithURL:assetUrl];
  SCFilter *exportFilter = [self.filterSwitcherView.selectedFilter copy];

  SCAssetExportSession *exportSession = [[SCAssetExportSession alloc] initWithAsset:asset];
  NSURL *urlFile = [NSURL URLWithString:[NSString stringWithFormat:@"%@/%@.mov",docsDir,fileName]];
  exportSession.outputUrl = [NSURL fileURLWithPath:[NSString stringWithFormat:@"%@",urlFile]];

  filterURL = exportSession.outputUrl;

  exportSession.videoConfiguration.filter = exportFilter;
  exportSession.videoConfiguration.preset = SCPresetHighestQuality;
  exportSession.audioConfiguration.preset = SCPresetHighestQuality;
  exportSession.videoConfiguration.maxFrameRate = 35;
  exportSession.outputFileType = AVFileTypeMPEG4;
  exportSession.delegate = self;
  exportSession.contextType = SCContextTypeAuto;
  self.exportSession = exportSession;

  [exportSession exportAsynchronouslyWithCompletionHandler:^{
      if (exportSession.error == nil) {
          [[UIApplication sharedApplication] beginIgnoringInteractionEvents];
          [exportSession.outputUrl saveToCameraRollWithCompletion:^(NSString * _Nullable path, NSError * _Nullable error) {
              [[UIApplication sharedApplication] endIgnoringInteractionEvents];

              if (error == nil) {
                //Success
              }
          }];

      } else {
          NSLog(@"Error: %@", exportSession.error);
      }
  }];
}