fade in fade out

gistfile1.txt

let avUrlAsset = AVAsset(URL: _url)
            let duration = avUrlAsset.duration
            let durationInSeconds = CMTimeGetSeconds(duration)
            let item = AVPlayerItem(asset: avUrlAsset, automaticallyLoadedAssetKeys:["duration"])
            let params = AVMutableAudioMixInputParameters(track: avUrlAsset.tracks.first! as AVAssetTrack)
            let firstSecond = CMTimeRangeMake(CMTimeMakeWithSeconds(0, 1), CMTimeMakeWithSeconds(15, 1))
            let lastSecond = CMTimeRangeMake(CMTimeMakeWithSeconds(durationInSeconds - 1, 1), CMTimeMakeWithSeconds(1, 1))
            params.setVolumeRampFromStartVolume(0, toEndVolume: 1, timeRange: firstSecond)
            params.setVolumeRampFromStartVolume(1, toEndVolume: 0, timeRange: lastSecond)
            let mix = AVMutableAudioMix()
            mix.inputParameters = [params]
            item.audioMix = mix