Currently you can upload up to 100MB Video Files & 10MB Photos.

Should you need to upload video of much greater size, please submit a support ticket, this is the same system that we use for bulk uploading, the easiest way is to add them to your OneDrive/Google Drive in a separate folder and share us the link as read only, we will then process the video files for you.
This is also referred to as the max upload file size.

These will only ever be used for this purpose, all ownership of the files still belong to yourself.