Process Live Photos on multiple threads

Question

I am processing a PHLivePhoto using .frameProcessor to modify each frame. The frames appear to be processed in sequence, which is slow. Can I get PHLivePhotoEditingContext.frameProcessor to take advantage of more than one core?

func processLivePhoto(input: PHContentEditingInput) {
    guard let context = PHLivePhotoEditingContext(livePhotoEditingInput: input)
        else { fatalError("not a Live Photo editing input") }
    context.frameProcessor = { frame, _ in
        let renderedFrame = expensiveOperation(using: frame.image)
        return renderedFrame
    }
    // ...logic for saving
}

score 0 · Answer 1 · answered Oct 04 '19 at 13:09

I'm afraid there's no way to parallelize the frame processing in this case. You have to keep in mind:

Video frames need to be written in order.
The more frames you would process in parallel, the more memory you would need.
Core Image is processing the frames on the GPU, which can usually only process one frame at a time anyways.
Your expensiveOperation is not really happening in the frameProcessor block anyways, since the actual rendering is handled by the framework outside this scope.

Process Live Photos on multiple threads

1 Answers1