I'm trying upload video and get this error

the error :

Illuminate\ Http\ Exceptions \ PostTooLargeException

    public function store(Request $request)
    {


        $validated = $request->validate([
            'small_title' => 'required',
            'big_title' => 'required',
            'image' => 'mimes:jpeg,png,jpg,gif',
            'video' => 'mimes:mp4,mov,ogg,qt | max:20000',
            'description' => 'required',
            'button_name' => 'required',
            'button_link' => 'required',

        ]);

        if ($request->has('image')){
            $photo = $request->image;
            $imageName = $photo->getClientOriginalName();
            $request->image->move(public_path('banner_image/'), $imageName);

        }

        if ($request->has('video')){
            $video = $request->video;
            $imageName = $video->getClientOriginalName();
            $request->video->move(public_path('banner_video/'), $imageName);
        }



        Banner::create([
            "page_id" => $request->page_id,
            "small_title" => $request->small_title,
            "big_title" => $request->big_title,
            "description" => $request->description,
            "banner_btn" => $request->button_name,
            "banner_link_btn" => $request->button_link,
            "small_title_ar" => $request->small_title_ar,
            "big_title_ar" => $request->big_title_ar,
            "description_ar" => $request->description_ar,
            "banner_btn_ar" => $request->banner_btn_ar,
            "banner_type" => $request->banner_type,
            "path" => $imageName,

        ]);
        session()->flash('success-add','Item Successfully Added.');
        $type = ($request->banner_type) ? "image" : "video";
        return redirect()->route('banner',$type);

    }