Create a Wordpress Function to affect a specific .txt file.

This is really pretty hard to explain, but I will try my best. I have a small automatic wordpress plugin. The plugin is created to protect my direct download links (to save bandwitch). For example: I have a direct download link - [login to view URL] People can use this link and use my bandwitch. To prevent hotlinking (stealing), I created a wordpress plugin which automatically generates new links that are "binded" to IP and expires after a certain time. Plugin automatically generates new links every time page is reloaded/opened. Direct link: [login to view URL] Protected link: [login to view URL] This plugin works perfect, but it is applied only to - the_content part of my wordpress based website. It uses this filter: add_filter( 'the_content', 'new_link_generator' ); Problem: I have some videos on my website which are using the same plugin for protection. For single-type videos it works just fine. The problem appears when I use playlist-type videos. My player reads JSON format .txt files for playlists: {"playlist":[ {"comment":"VIDEO_NAME","file":"VIDEO_LINK"} ]} The problem is what my plugin works only on >> the_content << part of my website, as I already said. It simply doesn't work in .txt files. What do I need? 1) Custom Field where I place my playlist links. 2) Every post must have it's own playlist. It is not just one playlist. I need tons of them. 3) The links in Playlist must be secured with my plugin. There are tons of websites running with similar method. I will provide some live examples (just websites who uses protected playlists). Let me know if you need some more information. Thank you.