Rendering the currently visible frame of a paused AVPlayer that has a custom video compositor

Q:  How can I re-render the currently visible frame of a paused AVPlayer that has a custom video compositor? I would like to update values that affect the rendered video while it is paused, and have those changes reflected in the currently visible frame.

A: To re-render a frame, you must set a new instance of AVVideoComposition to the player's current player item as shown in Listing 1.

Listing 1  Setting the video composition for a paused player to re-render the currently visible frame.

let asset:AVAsset = <#An asset#>

let playerItem:AVPlayerItem = <#A player's current player item#>

var applyComposition: ((AVAsynchronousCIImageFilteringRequest) -> Void)? = nil

applyComposition = { request in

      ...

}

let composition = AVVideoComposition(asset: asset,

          applyingCIFiltersWithHandler: applyComposition)

playerItem.videoComposition = composition   // Set the player item video composition.

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