MPNowPlayingInfoCenter duration not displayed

Question

I'm trying to write in Swift 2.2 (Xcode 7) an iOS 9 application that can play audio. All my files are read from internet, so i choosed StreamingKit and can be played in background from multiple ViewController, so i created a singleton that store the audio player instance.

I successfully make the player playing audio in background and display info in NowPlayingInfoCenter, but i can't get duration to work i got this result

When i start playing my file i initialize the MPNowPlayingInfo with theses lines

var nowPlayingInfo : Dictionary<String, AnyObject> = [
    MPNowPlayingInfoPropertyPlaybackRate : 1
]
if audioTitle != nil {
    nowPlayingInfo[MPMediaItemPropertyTitle] = audioTitle
}
else {
    nowPlayingInfo[MPMediaItemPropertyTitle] = NSLocalizedString("app_name", comment: "")
}
MPNowPlayingInfoCenter.defaultCenter().nowPlayingInfo = nowPlayingInfo

And when buffering is done i set additionnals informations with theses lines

var nowPlayingInfo = MPNowPlayingInfoCenter.defaultCenter().nowPlayingInfo

//Time
nowPlayingInfo!["MPNowPlayingInfoPropertyElapsedPlaybackTime"] = NSNumber(double: self.audioPlayer.progress)
nowPlayingInfo!["MPMediaItemPropertyPlaybackDuration"] = NSNumber(double: self.audioPlayer.duration)

//Is playing
nowPlayingInfo!["MPNowPlayingInfoPropertyPlaybackRate"] = NSNumber(double: self.isPlaying ? 1.0 : 0.0)

//State
if isError {
    nowPlayingInfo![MPMediaItemPropertyArtist] = NSLocalizedString("player_error", comment: "")
} else if isLoading {
    nowPlayingInfo![MPMediaItemPropertyArtist] = NSLocalizedString("player_loading", comment: "")
} else {
    nowPlayingInfo![MPMediaItemPropertyArtist] = NSString(string: self.audioArtist!)
}

MPNowPlayingInfoCenter.defaultCenter().nowPlayingInfo = nowPlayingInfo

An example (retrieved from debugger) of value passed in my NSNumber constructor above : progress = 1.892426303854875 duration = 62.85865814546887

I also tried to pass formatted NSString like this answer with for example theses values below retrieved in debugger : progress = 0:02 duration = 1:03

The player duration and seek bar still like the screenshot

Anyone can help me please ? Thanks