Class “FFMpegFFMpeg” not found

I installed ffmpeg on xampp by COMPOSER. I installed FFMPEG on windows before.
enter image description here

Then with the command composer require php-ffmpeg/php-ffmpeg installed php-ffmpeg
enter image description here

I use code below (from php-ffmpeg github) for a test but this does not work

<?php

require '../../phpMyAdmin/vendor/autoload.php';

$ffmpeg = FFMpegFFMpeg::create(); // line 5 that error referees to 
$video = $ffmpeg->open('video.mpg');
$video
    ->filters()
    ->resize(new FFMpegCoordinateDimension(320, 240))
    ->synchronize();
$video
    ->frame(FFMpegCoordinateTimeCode::fromSeconds(10))
    ->save('frame.jpg');
$video
    ->save(new FFMpegFormatVideoX264(), 'export-x264.mp4')
    ->save(new FFMpegFormatVideoWMV(), 'export-wmv.wmv')
    ->save(new FFMpegFormatVideoWebM(), 'export-webm.webm');

?>

This is the error I encounter.
enter image description here

I read many and many similar questions but almost all of them suggest require '../../phpMyAdmin/vendor/autoload.php'; that I have it in my code.