Class not found after installing library

I just installed this library:

https://video.aminyazdanpanah.com/start

By running:

composer require aminyazdanpanah/php-ffmpeg-video-streaming

In my class, I put the following:

<?php

namespace App\Jobs;

use Streaming\FFMpeg;

But when the job runs, it returns the following error:

Symfony\Component\Debug\Exception\FatalThrowableError: Class 'Streaming\FFMpeg' not found in /home/vagrant/project/app/Jobs/MyJob.php:114

Why? What have I missed?

via Chebli Mohamed