Video formats

I’ve noticed that when I upload an m4v video the thumbnail is generated automatically and embedded using the Add Media option.

When I’ve uploaded mp4 (I think) there’s been no thumbnail.

Can anyone tell me why this is? I’m assuming that it’sa function of the software that’s used to export the video? Or is it a feature of that format? And that WordPress knows how to get the thumbnail from the video? Is there any other format that WordPress would auto generate the thumbnail and be a good format to watch a less than 5 minute video at a good quality?

Thanks in anticipation.

• This topic was modified 2 years, 8 months ago by Jan Dembowski. Reason: Moved to Fixing WordPress, this is not an Everything else WordPress topic