How can I make the process that filtering saved video in photo library in iOS?

I got URLs of videos in the library using AssetsLibrary framework,

then, made a preview for the video.

Next step, I wanna make filtering process for video using CIFilter.

In case of real time issue, I made video filter process using AVCaptureVideoDataOutputSampleBufferDelegate.

But in case of saved video, I don't know how to make filter process.

Do I use AVAsset? If I must use that, how can I filter it? and how to save it?

always thank you.