Accounting for current time when panning to scrub video - ios

Question

This is the code related to panning/ scrubbable video. The current issue occurs when the second swipe gesture has a delta from the last position of the first swipe. In other words this code needs to take into account the current time of the video to prevent the skip.
```
func didSwipe(panGR: UIPanGestureRecognizer) {
let translation = panGR.translationInView(self.view)
var horizontalTranslation = Float(translation.x)
let durationInSeconds = Float(CMTimeGetSeconds(self.playerView.player.player.currentItem!.asset.duration))
// Using 275 as the limit for delta along x
let translationLimit: Float = 275
let minTranslation: Float = -1 * translationLimit
let maxTranslation: Float = translationLimit
if horizontalTranslation > maxTranslation {
horizontalTranslation = maxTranslation
}
if horizontalTranslation < minTranslation {
horizontalTranslation = minTranslation
}
let timeToSeekTo = normalize(horizontalTranslation , minDelta: minTranslation, maxDelta: maxTranslation, minDuration: 0, maxDuration: durationInSeconds)
print("horizontal translation \(horizontalTranslation) \n timeToSeekTo: \(timeToSeekTo)")
self.playerView.player.startScrubbing()
self.playerView.player.scrub(timeToSeekTo)
self.playerView.player.stopScrubbing()
}
func normalize(delta: Float, minDelta: Float, maxDelta: Float, minDuration: Float, maxDuration: Float) -> Float {
let result = ((delta - minDelta) * (maxDuration - minDuration) / (maxDelta - minDelta) + minDuration)
return result
}
```
I am setting the starting time to be exactly at half of the video length. This produces a good first swipe result in either direction. It has a noticeable skip on the second and subsequent swipes because it is not accounting for the current time of the video (i think).

Answer 1

Here's the code I wrote that employs the normalize function, and displays the current rate (and a Play icon that changes size according to the player rate:
- (IBAction)handlePanGesture:(UIPanGestureRecognizer *)sender {
if (sender.state == UIGestureRecognizerStateBegan) {
[self.rateLabel setHidden:FALSE];
[self animatePlayerControl:#"▷" size:1.0];
[UIView animateWithDuration:0.375 animations:^{
(self.playerControlsLabel).alpha = 0.5f;
}];
} else if (sender.state == UIGestureRecognizerStateEnded) {
[self.rateLabel setHidden:FALSE]; // set to TRUE after testing or remove hiding altogether
//[self.delegate setRate:oldRate];
//[self animatePlayerControl:#"□" size:1.0];
//[_ChromaEpsilonGammaAppDelegate.playerViewController setRate:0.0];
//[_ChromaEpsilonGammaAppDelegate.playerViewController stop];
[UIView animateWithDuration:0.375 animations:^{
(self.playerControlsLabel).alpha = 0.0f;
}];
} else if (sender.state == UIGestureRecognizerStateChanged){
CGPoint location = [sender locationInView:self];
float nlx = ((location.x / ((CGRectGetMidX(self.frame) / (self.frame.size.width / 2.0)))) / (self.frame.size.width / 2.0)) - 1.0;
//float nly = ((location.y / ((CGRectGetMidY(self.view.frame) / (self.view.frame.size.width / 2.0)))) / (self.view.frame.size.width / 2.0)) - 1.0;
nlx = nlx * 2.0;
[self.delegate setRate:nlx];
if (nlx > 0.0) [self animatePlayerControl:#"▷" size:nlx];
else if (nlx < 0.0) [self animatePlayerControl:#"◁" size:fabs(nlx)];
(self.rateLabel).text = [NSString stringWithFormat:#"%.2f", [self.delegate rate]];
}
}
The label setup, which can go anywhere, not just in the drawRect method:
- (void)drawRect:(CGRect)rect {
(self.brightnessLabel).textColor = [UIColor colorWithWhite:1.0 alpha:1.0];
(self.brightnessLabel).font = [UIFont preferredFontForTextStyle:#"Apple Symbol"];
(self.brightnessLabel).textAlignment = NSTextAlignmentCenter;
(self.contrastLabel).textColor = [UIColor colorWithWhite:1.0 alpha:1.0];
(self.contrastLabel).font = [UIFont preferredFontForTextStyle:#"Apple Symbol"];
(self.contrastLabel).textAlignment = NSTextAlignmentCenter;
_attrsDictionary = #{NSFontAttributeName: [UIFont systemFontOfSize:24.0 weight:UIFontWeightLight]};
}
And, the auto-adjusting Player icon size code:
- (void)animatePlayerControl:(NSString *)labelText size:(float)size {
(self.playerControlsLabel).textColor = [UIColor colorWithWhite:1.0 alpha:1.0];
(self.playerControlsLabel).font = [UIFont preferredFontForTextStyle:#"Apple Symbol"];
(self.playerControlsLabel).textAlignment = NSTextAlignmentCenter;
NSDictionary *attrsDictionary = #{NSFontAttributeName: [UIFont systemFontOfSize:fabs(48.0 * size) weight:UIFontWeightUltraLight]};
NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:labelText attributes:attrsDictionary];
(self.playerControlsLabel).attributedText = attrString;
}
The player icon is simply a character from the Apple Symbol font.