How to deal with [Error creating thumbnail] in mediawiki when upload video by TimedMediaHandler?

Question

I am creating my first MediaWiki, and I want to upload videos locally instead of using the YouTuBe links.

I have installed the TimedMediaHandler extension, I am sure as I can see it on the version of special pages. I also installed the ffmpeg as it asked.

I used these below in the LocalSettings.php:

wfLoadExtension（ 'TimedMediaHandler' ）;
$wgFFmpegLocation = 'C：\ffmpeg\bin\ffmpeg';
$wgMaxShellMemory = 780000;
$wgMaxShellFileSize = 1024 * 512;
$wgMaxShellTime = 60 * 60;

$wgFileExtensions = [
'png'， 'GIF'， 'jpg'， 'JPEG'， 'JP2'， 'WebP'， 'PPT'， 'PDF'， 'PSD'，
'mp3'， 'xls'， 'xlsx'， 'swf'， 'doc'， 'docx'， 'odt'， 'odc'， 'odp'，
'ODG'， 'MPP'， 'PPTX'， 'MP4'
];

But when I upload a video, no matter which kind of type (mp4,mpg,webm,ogv), there is always a [Error creating thumbnail], but the picture works.

enter image description here

When I use [[file:111.mpg]] in the source code of the main page as it asked, it also shows the word[Error creating thumbnail] and links to the file page.

I don't know how to deal with it...please help me!

I want to upload the video locally in MediaWiki as the TimedMediaHandler described.