Joomla uses it’s own php.ini for the administration panel. So although we had change our values in the root php.ini the upload_max_filesize remained at 8M.
To increase that we need to edit the php.ini located under the administrator dir and add those two lines
upload_max_filesize = 50M post_max_size = 50M
Also have a look at your Media Manager Component configuration and increase the limit accordingly.