How to change CIFilter value of video using UISlider?

Question

I am trying to add CIFilters to video. But I change the values using UISliders because of AVPlayer take time to play filter added video. I search of this issue, UISlider values continuously changing and it takes float values as well. Because of every time filter add to video and play. I want to know how to change values of CIFilter and without delay of AVPlayer when slider value change continuously.

float value = sender.value;
CIFilter *filter = [CIFilter filterWithName:@"CIColorControls"];
AVVideoComposition *composition = [AVVideoComposition videoCompositionWithAsset:tempAVAsset applyingCIFiltersWithHandler:
                                   ^(AVAsynchronousCIImageFilteringRequest *request){
                                       NSError *err = nil;
                                       CIImage *filtered = [request.sourceImage imageByClampingToExtent];
                                       [filter setDefaults];
                                       [filter setValue:filtered forKey:kCIInputImageKey];

                                       [filter setValue:[NSNumber numberWithFloat:0.00] forKey:@"inputSaturation"];
                                       [filter setValue:[NSNumber numberWithFloat:0.00] forKey:@"inputBrightness"];
                                       [filter setValue:[NSNumber numberWithFloat:value] forKey:@"inputContrast"];

                                       CIImage *output = [filter.outputImage imageByCroppingToRect:request.sourceImage.extent];
                                       if (filtered)
                                           [request finishWithImage:output context:nil];
                                       else
                                           [request finishWithError:err];

                                   }];

Answer 1

You can just change the filter parameter outside of your composition block when the slider value changes and don't re-set it inside the block. So just do

[adjustFilter setValue:[NSNumber numberWithFloat:sender.value] forKey:@"inputContrast"];

inside your valueChanged callback instead of inside the composition block. This way the filter always gets the most current value and will use it for the next video frame.

Edit:

Here are some parts of a possible implementation inside a view controller:

@interface DemoViewController ()

@property (strong, nonatomic) CIFilter *filter;
@property (strong, nonatomic) AVPlayer *player;
@property (strong, nonatomic) AVAsset *tempAVAsset;

@end

@implementation DemoViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // setup filter
    self.filter = [CIFilter filterWithName:@"CIColorControls"];
    [self.filter setDefaults];
    [self.filter setValue:[NSNumber numberWithFloat:0.00] forKey:@"inputSaturation"];
    [self.filter setValue:[NSNumber numberWithFloat:0.00] forKey:@"inputBrightness"];

    AVVideoComposition *composition = [AVVideoComposition videoCompositionWithAsset:self.tempAVAsset applyingCIFiltersWithHandler:
        ^(AVAsynchronousCIImageFilteringRequest *request){
            NSError *err = nil;
            CIImage *filtered = [request.sourceImage imageByClampingToExtent];

            [self.filter setValue:filtered forKey:kCIInputImageKey];
            CIImage *output = [self.filter.outputImage imageByCroppingToRect:request.sourceImage.extent];
            if (filtered)
               [request finishWithImage:output context:nil];
            else
               [request finishWithError:err];
        }
    ];

    // setup player with composition
    // ...
}


- (IBAction)sliderValueChanged:(UISlider*)sender
{
    // get the new slider value and assign it to the filter
    [self.filter setValue:[NSNumber numberWithFloat:sender.value] forKey:@"inputContrast"];
}

@end