Traditional LRU file caching doesn't work well with multimedia files only because of that the access patterns for movies are different from those of the text files.
The basic concept/idea behind the traditional LRU buffer caches is that after a block is used, it should be kept in the cache when it is needed again quickly with multimedia system, the general access pattern is that a movie is viewed from beginning to end sequentially.
Unlikely, a block is to be used a second time unless the user rewinds the movie to see some scene again.
Consequently, the normal caching techniques don't work. However, caching can still help, but only if used differently.