Сергей Дунаев

Из того кода, что написан, максимально приближенный рабочий вариант будет выглядеть следующим образом. Чтобы хорошо разобраться в теме рекомендую посмотреть этот курс по Collection View.

import UIKit
import AVKit

class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {
    
    let imagesCellId = "ImageCellId"
    let albumCellId = "AlbumCellId"
    
    let collectionView: UICollectionView = {
        let layout = UICollectionViewFlowLayout()
        layout.minimumLineSpacing = 16
        layout.scrollDirection = .vertical
        layout.itemSize = CGSize(width: 50, height: 50)
        
        let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
        cv.backgroundColor = .clear
        
        return cv
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setupViews()
    }
    
    func setupViews() {
        collectionView.register(VideoCell.self, forCellWithReuseIdentifier: imagesCellId)
        collectionView.register(PreviewCell.self, forCellWithReuseIdentifier: albumCellId)
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.allowsSelection = true
        collectionView.isUserInteractionEnabled = true
        
        view.addSubview(collectionView)
        
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        collectionView.topAnchor.constraint(equalTo: view.topAnchor, constant: 20).isActive = true
        collectionView.bottomAnchor.constraint(equalTo:  view.bottomAnchor, constant: 5).isActive = true
        collectionView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0).isActive = true
        collectionView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 0).isActive = true
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        if indexPath.section == 1 {
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: albumCellId, for: indexPath) as! PreviewCell
            cell.backgroundColor = UIColor.red
            return cell
        }
        
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: imagesCellId, for: indexPath) as! VideoCell
        
        cell.backgroundColor = UIColor.green
        return cell
    }
    
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 2
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 1
    }
    
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        // Вот тут совсем не понятно, что хотел сказать автор
        
//        collectionView.selectItem(at: IndexPath(item: 0, section: 0), animated: true, scrollPosition: .left)
//        collectionView(collectionView, didSelectItemAt: IndexPath(item: 0, section: 0))
        
        print("Выбрана ячейка: (\(indexPath.section), \(indexPath.item))")
    }
    
}

class VideoCell: UICollectionViewCell, AVPlayerViewControllerDelegate {
    var videoPlayerController = AVPlayerViewController()
}
class PreviewCell: UICollectionViewCell {

}