Ios G图像HoughtTransferMLined检测器闪烁/闪烁

我正在使用Brad Larson的示例项目中的GPuimageHoughtTransferorMLinedetector，这是我的一个使用故事板的应用程序。一切正常，但屏幕上闪烁着这个过滤器。使用滑块时，闪烁停止。有人能帮忙吗？或者有人知道为什么会这样吗

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你有没有想过？没有，我暂时搁置。你呢。。。有什么事吗？还没有。我可以找到并显示台词，但它仍在闪烁。

#import <UIKit/UIKit.h>
#import "GPUImage.h"
@interface ViewController : UIViewController<GPUImageVideoCameraDelegate>{
    GPUImageVideoCamera *videoCamera;
    GPUImageView *filterView;
    GPUImageOutput<GPUImageInput> *filter;
 __unsafe_unretained UISlider *slider;
}
@property(readwrite, unsafe_unretained, nonatomic) IBOutlet UISlider *slider;
- (IBAction)updateSlider:(id)sender;
@end

#import "ViewController.h"

@interface ViewController (){
}
@end
@implementation ViewController
@synthesize slider;
- (void)viewDidLoad {
[super viewDidLoad];

CGRect mainScreenFrame = [[UIScreen mainScreen] applicationFrame];
UIView *primaryView = [[UIView alloc] initWithFrame:mainScreenFrame];
primaryView.backgroundColor = [UIColor blueColor];
self.view = primaryView;

filterView = [[GPUImageView alloc] initWithFrame:CGRectMake(primaryView.frame.origin.x,primaryView.frame.origin.y, primaryView.frame.size.width,primaryView.frame.size.height)];
[primaryView addSubview:filterView];
[filterView addSubview:slider];
videoCamera = [[GPUImageVideoCamera alloc] initWithSessionPreset:AVCaptureSessionPreset640x480 cameraPosition:AVCaptureDevicePositionBack];
videoCamera.outputImageOrientation = UIInterfaceOrientationPortrait;

[slider setMinimumValue:0.2];
[slider setMaximumValue:1.0];
[slider setValue:0.6];

filter = [[GPUImageHoughTransformLineDetector alloc] init];
[(GPUImageHoughTransformLineDetector *)filter setLineDetectionThreshold:0.60];
[filter addTarget:filterView];
[videoCamera addTarget:filter];

GPUImageAlphaBlendFilter *blendFilter = [[GPUImageAlphaBlendFilter alloc] init];
[blendFilter forceProcessingAtSize:CGSizeMake(480.0, 640.0)];
GPUImageGammaFilter *gammaFilter = [[GPUImageGammaFilter alloc] init];
[videoCamera addTarget:gammaFilter];
[gammaFilter addTarget:blendFilter];
[blendFilter addTarget:filterView];

GPUImageLineGenerator *lineGenerator = [[GPUImageLineGenerator alloc] init];
[lineGenerator forceProcessingAtSize:CGSizeMake(480.0, 640.0)];
[lineGenerator setLineColorRed:1.0 green:0.0 blue:0.0];
[(GPUImageHoughTransformLineDetector *)filter setLinesDetectedBlock:^(GLfloat* lineArray, NSUInteger linesDetected, CMTime frameTime){
[lineGenerator renderLinesFromArray:lineArray count:linesDetected frameTime:frameTime];
}];
[lineGenerator addTarget:blendFilter];
[videoCamera startCameraCapture];
videoCamera.runBenchmark = YES;
}

- (IBAction)updateSlider:(id)sender {
[videoCamera resetBenchmarkAverage];
[(GPUImageHoughTransformLineDetector *)filter setLineDetectionThreshold:[(UISlider*)sender value]];
}
@end