Photo and Video Gallery for clients

I need professional look photos and video gallery for my clients in my existing website. I would not mind if you want to build the gallery from any free existing gallery software but I have some spacific need. 1) The client will need prior registration and approved by us before being able to log into the site. 2) All the photos or video should not be able to download without using download function in the gallery. 3) I like to have low quality photo appear on the site but when download the photo, it should give high quality photo. 4) Once a client downlaod a photo, email will send to us with detail of the client and the photo. This information will also be stored in the admin page of the gallery. 5) For video, the file format will be mpeg 2 or mpeg 4. It should be able to play on the site. It would be great if you can make low quality video appear on the site without we uploading two different file format. I will need a space for short explanation of the video like photo caption but more space will be needed. 6) Once a client want to purchease, it should give two option, one - download into a client computer or send to client ftp site with a client desire file name. 7) I will need a text page where all the updated information will appear. I would also need sending update information to all the clients email addresses and perhaps, sms to their mobile numbers. 8)At his stage, I don't need online credit card payment but it should be able to do it in the future. The whole gallery should be able to maintain on the website with backadmin and for large video file, we could upload via ftp and update the link in the admin page. I might need to add some small extra need as the project is being implemeted. I would prefre you write this on php and mysql but I would not mind if you want to use flash.