title: How to save GPUImage filtered video with Audio?
body: <p>I have already apply filter on video. But the issue with saving it in Camera roll with Audio output. But unfortunately I am failing to save it.</p>
  
  <p>see below code.</p>
  
  <pre><code>-(IBAction)saveVideo:(id)sender{
  
      NSString *pathToMovie = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Movie.mov"];
      unlink([pathToMovie UTF8String]); // If a file already exists, AVAssetWriter won't let you record new frames, so delete the old movie
      NSURL *movieURL = [NSURL fileURLWithPath:pathToMovie];
  
      _movieWriter = [[GPUImageMovieWriter alloc] initWithMovieURL:movieURL size:CGSizeMake(720.0, 1280.0)];
      _movieWriter.shouldPassthroughAudio = YES;
      //_movieWriter.assetWriter.movieFragmentInterval = kCMTimeInvalid;
      _movieWriter.hasAudioTrack = YES;
      _movieFile.audioEncodingTarget = self.movieWriter;
      [_filter addTarget:_movieWriter];
      [_movieFile enableSynchronizedEncodingUsingMovieWriter:_movieWriter];
  
      [_movieWriter startRecording];
      __block GPUImageOutput&lt;GPUImageInput&gt; *weekfilter = _filter;
      __block GPUImageMovieWriter *weekMovieWriter = _movieWriter;
      ViewControllerFilters* __weak weakSelf = self;
  
      [_movieWriter setCompletionBlock:^{
          [weekfilter removeTarget:weekMovieWriter];
          [weekMovieWriter finishRecording];
  
          dispatch_async(dispatch_get_main_queue(), ^{
              // [timer invalidate];
              //self.progressLabel.text = @"100%";
  //            [[SoundManager sharedManager] stopAnimating];
  //            [weakSelf performSegueWithIdentifier:export sender:movieURL];
              [weakSelf saveToCameraRoll:movieURL];
          });
      }];
  }
  </code></pre>
  
  <p><strong>I got the log can't write frame. and receive memory warning and app crash.</strong></p>