Problems generating thumbnails with ffmpeg-php

[Morthian]

The script below should generate a thumbnail from the middle of the video, however, it instead creates thumbnails from seemingly random frames of the video.

Furthermore, depending on the video, the following PHP error sometimes occurs:
"Fatal error: Call to a member function toGDImage() on a non-object..."

Any ideas?

<?php

$media = new ffmpeg_movie('video.mp4');
$frame_count = $media->getFrameCount();
$frame = $media->getFrame(round($frame_count / 2));
$thumbnail_image = $frame->toGDImage();
        
header('Content-type: image/jpeg');
imagejpeg($thumbnail_image);

?>

[PHPycho]

Have you installed the extension of ffmpeg in your server ?

[Morthian]

Have you installed the extension of ffmpeg in your server ?

Of course. The script often succeeds at producing a thumbnail, but the thumbnail is not from the half-way point of the video from which it should be. When the script does not succeed, it produces the fatal error I mentioned in my initial post.

For now I think I will execute ffmpeg directly to generate thumbnails.