Delete them in list view. Re-upload with a better connection.
If videos are stuck in processing (typically only when the internet connection is interrupted during upload), delete them and try again. This can be accomplished by switching to list view (middle of 3 buttons on the left side of the top bar when viewing "All Media"). Then select the stuck videos and select "Delete" in the bottom right corner. Videos should be re-uploaded when the internet connection is strong and will be uninterrupted.