I received a mp4 video in a text on my Nokia Lumia 920. How can I save the video to the camera roll (photos)? The 'save' option is not available as it is with a photo.
You will have to use a workaround to do this: instead of trying to saving the video itself, forward the message containing the video to your email. Then download it on your computer and sync it back to your phone (through OneDrive, the Windows Phone app, or File Explorer).
You are not alone in wanting this feature. There are 3 posts that have been created on the Windows Phone User Voice site that request this feature: